A 2D chiral microcavity based on apparent circular dichroism

Engineering asymmetric transmission between left-handed and right-handed circularly polarized light in planar Fabry-Pérot (FP) microcavities would enable a variety of chiral light-matter phenomena, with applications in spintronics, polaritonics, and chiral lasing. Such symmetry breaking, however, generally requires Faraday rotators or nanofabricated polarization-preserving mirrors. We present a simple solution requiring no nanofabrication to induce asymmetric transmission in FP microcavities, preserving low mode volumes by embedding organic thin films exhibiting apparent circular dichroism (ACD); an optical phenomenon based on 2D chirality. Importantly, ACD interactions are opposite for counter-propagating light. Consequently, we demonstrated asymmetric transmission of cavity modes over an order of magnitude larger than that of the isolated thin film. Through circular dichroism spectroscopy, Mueller matrix ellipsometry, and simulation using theoretical scattering matrix methods, we characterize the spatial, spectral, and angular chiroptical responses of this 2D chiral microcavity.

Theory predicts 2D chiral polaritons based on achiral Fabry-Pérot cavities using apparent circular dichroism

Realizing polariton states with high levels of chirality offers exciting prospects for quantum information, sensing, and lasing applications. Such chirality must emanate from either the involved optical resonators or the quantum emitters. Here, we theoretically demonstrate a rare opportunity for realizing polaritons with so-called 2D chirality by strong coupling of the optical modes of (high finesse) achiral Fabry-Pérot cavities with samples exhibiting "apparent circular dichroism" (ACD). ACD is a phenomenon resulting from an interference between linear birefringence and dichroic interactions. By introducing a quantum electrodynamical theory of ACD, we identify the design rules based on which 2D chiral polaritons can be produced, and their chirality can be optimized.

Theory predicts UV/vis-to-IR photonic down conversion mediated by excited state vibrational polaritons

This work proposes a photophysical phenomenon whereby ultraviolet/visible (UV/vis) excitation of a molecule involving a Franck-Condon (FC) active vibration yields infrared (IR) emission by strong coupling to an optical cavity. The resulting UV/vis-to-IR photonic down conversion process is mediated by vibrational polaritons in the electronic excited state potential. It is shown that the formation of excited state vibrational polaritons (ESVP) via UV/vis excitation only involve vibrational modes with both a non-zero FC activity and IR activity in the excited state. Density functional theory calculations are used to identify 1-Pyreneacetic acid as a molecule with this property and the dynamics of ESVP are modeled. Overall, this work introduces an avenue of polariton chemistry where excited state dynamics are influenced by the formation of vibrational polaritons. Along with this, the UV/vis-to-IR photonic down conversion is potentially useful in both sensing excited state vibrations and quantum transduction schemes.

Exciton annihilation in molecular aggregates suppressed through qu antum interference

Exciton-exciton annihilation (EEA), an important loss channel in optoelectronic devices and photosynthetic complexes, has conventionally been assumed to be an incoherent, diffusion-limited process. Here we challenge this assumption by experimentally demonstrating the ability to control EEA in molecular aggregates using the quantum phase relationships of excitons. We employed time-resolved photoluminescence microscopy to independently determine exciton diffusion constants and annihilation rates in two substituted perylene diimide aggregates featuring contrasting excitonic phase envelopes. Low-temperature EEA rates were found to differ by more than two orders of magnitude for the two compounds, despite comparable diffusion constants. Simulated rates based on a microscopic theory, in excellent agreement with experiments, rationalize this EEA behaviour based on quantum interference arising from the presence or absence of spatial phase oscillations of delocalized excitons. These results offer an approach for designing molecular materials using quantum interference where low annihilation can coexist with high exciton concentrations and mobilities.

A Mean-Field Treatment of Vacuum Fluctuations in Strong Light-Matter Coupling

Mean-field mixed quantum-classical dynamics could provide a much-needed means to inexpensively model quantum electrodynamical phenomena by describing the optical field and its vacuum fluctuations classically. However, this approach is known to suffer from an unphysical transfer of energy out of the vacuum fluctuations when the light-matter coupling becomes strong. We highlight this issue for the case of an atom in an optical cavity and resolve it by introducing an additional set of classical coordinates to specifically represent vacuum fluctuations whose light-matter interaction is scaled by the instantaneous ground-state population of the atom. This not only rigorously prevents the aforementioned unphysical energy transfer but is also shown to yield a radically improved accuracy in terms of the atomic population and the optical field dynamics, generating results in excellent agreement with full quantum calculations. As such, the resulting method emerges as an attractive solution for the affordable modeling of strong light-matter coupling phenomena involving macroscopic numbers of optical modes.

Overcoming positivity violations for density matrices in surface hopping

Fewest-switches surface hopping (FSSH) has emerged as one of the leading methods for modeling the quantum dynamics of molecular systems. While its original formulation was limited to adiabatic populations, the growing interest in the application of FSSH to coherent phenomena prompts the question of how one should construct a complete density matrix based on FSSH trajectories. A straightforward solution is to define adiabatic coherences based on wavefunction coefficients. In this paper, we demonstrate that inconsistencies introduced in the density matrix through such treatment may lead to a violation of positivity. We furthermore show that a recently proposed coherent generalization of FSSH results in density matrices that satisfy positivity while yielding improved accuracy throughout much (but not all) of parameter space.

A reciprocal-space formulation of surface hopping

Surface hopping has seen great success in describing molecular phenomena where electronic excitations tend to be localized, but its application to materials with band-like electronic properties has remained limited. Here, we derive a formulation of fewest-switches surface hopping where both the quantum and classical equations of motion are solved entirely in terms of reciprocal-space coordinates. The resulting method is directly compatible with band structure calculations and allows for the efficient description of band-like phenomena by means of a truncation of the Brillouin zone. Using the Holstein and Peierls models as examples, we demonstrate the formal equivalence between real-space and reciprocal-space surface hopping and assess their accuracy against mean-field mixed quantum-classical dynamics and numerically exact results. Having very similar equations of motion, reciprocal-space surface hopping can be straightforwardly incorporated in existing (real-space) surface hopping implementations.

Theory of Apparent Circular Dichroism Reveals the Origin of Inverted and Noninverted Chiroptical Response under Sample Flipping

Circular dichroism (CD) finds widespread application as an optical probe for the structure of molecules and supramolecular assemblies. Its underlying chiral light-matter interactions effectively couple between photonic spin states and select quantum-mechanical degrees of freedom in a sample, implying an intricate connection with photon-to-matter quantum transduction. However, effective transduction implementations likely require interactions that are antisymmetric with respect to the direction of light propagation through the sample, yielding an inversion of the chiroptical response upon sample flipping, which is uncommon for CD. Recent experiments on organic thin films have demonstrated such chiroptical behavior, which was attributed to "apparent CD" resulting from an interference between the sample's linear birefringence and linear dichroism. However, a theory connecting the underlying optical selection rules to the microscopic electronic structure of the constituent molecules remains to be formulated. Here, we present such a theory based on a combination of Mueller calculus and a Lorentz oscillator model. The theory reaches good agreement with experimental CD spectra and allows for establishing the (supra)molecular design rules for maximizing or minimizing this chiroptical effect. It furthermore highlights that, in addition to antisymmetrically, it can manifest symmetrically such that no chiroptical response inversion occurs, which is a consequence of a helical stacking of molecules in the light propagation direction.

Analytic and numerical vibronic spectra from quasi-classical trajectory ensembles

The truncated Wigner approximation to quantum dynamics in phase space is explored in the context of computing vibronic line shapes for monomer linear optical spectra. We consider multiple model potential forms including a shifted harmonic oscillator with both equal and unequal frequencies on the ground and excited state potentials as well as a shifted Morse potential model. For the equal-frequency shifted harmonic oscillator model, we derive an analytic expression for the exact vibronic line shape that emphasizes the importance of using a quantum mechanical distribution of phase space initial conditions. For the unequal-frequency shifted harmonic oscillator model, we are no longer able to obtain an exact expression for the vibronic line shape in terms of independent deterministic classical trajectories. We show how one can rigorously account for corrections to the truncated Wigner approximation through nonlinear responses of the line shape function to momentum fluctuations along a classical trajectory and demonstrate the qualitative improvement in the resulting spectrum when the leading-order quantum correction is included. Finally, we numerically simulate absorption spectra of a highly anharmonic shifted Morse potential model. We find that, while finite quantization and the dissociation limit are captured with reasonable accuracy, there is a qualitative breakdown of the quasi-classical trajectory ensemble's ability to describe the vibronic line shape when the relative shift in Morse potentials becomes large. The work presented here provides clarity on the origin of unphysical negative features known to contaminate absorption spectra computed with quasi-classical trajectory ensembles.

A reciprocal-space formulation of mixed quantum-classical dynamics

We derive a formulation of mixed quantum-classical dynamics for modeling electronic carriers interacting with phonons in reciprocal space. For dispersionless phonons, we start by expressing the real-space classical coordinates in terms of complex variables. Taking these variables as a Fourier series then yields the reciprocal-space coordinates. Evaluating the electron-phonon interaction term through Ehrenfest's theorem, we arrive at a reciprocal-space formalism that is equivalent to mean-field mixed quantum-classical dynamics in real space. This equivalence is numerically verified for the Holstein and Peierls models, for which we find the reciprocal-space Hellmann-Feynman forces to involve momentum-derivative contributions in addition to the position-derivative terms commonly seen in real space. To illustrate the advantage of the reciprocal-space formulation, we present a proof of concept for the inexpensive modeling of low-momentum carriers interacting with phonons using a truncated reciprocal-space basis, which is not possible within a real-space formulation.

Charge-transfer biexciton annihilation in a donor-acceptor co-crystal yields high-energy long-lived charge carriers

Organic donor-acceptor (D-A) co-crystals have attracted much interest due to their important optical and electronic properties. Co-crystals having ⋯DADA⋯ π-stacked morphologies are especially interesting because photoexcitation produces a charge-transfer (CT) exciton, D˙+-A˙-, between adjacent D-A molecules. Although several studies have reported on the steady-state optical properties of this type of CT exciton, very few have measured the dynamics of its formation and decay in a single D-A co-crystal. We have co-crystallized a peri-xanthenoxanthene (PXX) donor with a N,N-bis(3-pentyl)-2,5,8,11-tetraphenylperylene-3,4:9,10-bis(dicarboximide) (Ph4PDI) acceptor to give an orthorhombic PXX-Ph4PDI ⋯DADA⋯ π-stacked co-crystal with a CT transition dipole moment that is perpendicular to the transition moments for S n ← S0 excitation of PXX and Ph4PDI. Using polarized, broadband, femtosecond pump-probe microscopy, we have determined that selective photoexcitation of Ph4PDI in the single co-crystal results in CT exciton formation within the 300 fs instrument response time. At early times (0.3 ≤ t ≤ 500 ps), the CT excitons decay with a t -1/2 dependence, which is attributed to CT biexciton annihilation within the one-dimensional ⋯DADA⋯ π-stacks producing high-energy, long-lived (>8 ns) electron-hole pairs in the crystal. These energetic charge carriers may prove useful in applications ranging from photovoltaics and opto-electronics to photocatalysis.

Quantum biology revisited

Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.

Multiset Matrix Product State Calculations Reveal Mobile Franck-Condon Excitations Under Strong Holstein-Type Coupling

We show that the dynamics of (vertical) Franck-Condon excitations in the regime where Holstein-coupled vibrational modes mix strongly with electronic degrees of freedom sharply contrasts with the known self-localized behavior of vibrationally relaxed excitations. Instead, the strongly coupled modes are found to periodically induce resonances between interacting electronic sites, during which effective excitation transfer occurs, allowing Franck-Condon excitations to attain substantial mean square displacements under conditions where relaxed excitations are essentially trapped to a single site. In demonstrating this behavior, we employ a multiset matrix product state formalism. We find this tensor network state method to be a remarkably efficient and accurate approach for the notoriously difficult problem posed by the Holstein model in the regime where the electronic coupling, the vibrational quantum, and the vibrational reorganization energy are comparable in magnitude.

Many-body simulation of two-dimensional electronic spectroscopy of excitons and trions in monolayer transition metal dichalcogenides

Indications of coherently interacting excitons and trions in doped transition metal dichalcogenides have been measured as quantum beats in two-dimensional electronic spectroscopy, but the microscopic principles underlying the optical signals of exciton-trion coherence remain to be clarified. Here we present calculations of two-dimensional spectra of such monolayers based on a microscopic many-body formalism. We use a parameterized band structure and a static model dielectric function, although a full ab initio implementation of our formalism is possible in principle. Our simulated spectra are in excellent agreement with experiments, including the quantum beats, while revealing the interplay between excitons and trions in molybdenum- and tungsten-based transition metal dichalcogenides. Quantum beats are confirmed to unambiguously reflect the exciton-trion coherence time in molybdenum compounds, but are shown to provide a lower bound to the coherence time for tungsten analogues due to a destructive interference from coexisting singlet and triplet trions.

2D electronic spectroscopy found experimental indications of coherently interacting excitons and trions in doped transition metal dichalcogenides (TMDCs). Here, the authors perform simulations of 2D spectra of monolayer TMDCs based on a many-body formalism, allowing to relate exciton-trion coherence to quantum beats based on microscopic principles.

Vibronic exciton theory of singlet fission. I. Linear absorption and the anatomy of the correlated triplet pair state

Recent time-resolved spectroscopic experiments have indicated that vibronic coupling plays a vital role in facilitating the process of singlet fission. In this work, which forms the first article of a series, we set out to unravel the mechanisms underlying singlet fission through a vibronic exciton theory. We formulate a model in which both electronic and vibrational degrees of freedom are treated microscopically and non-perturbatively. Using pentacene as a prototypical material for singlet fission, we subject our theory to comparison with measurements on polarization-resolved absorption of single crystals, and employ our model to characterize the excited states underlying the absorption band. Special attention is given to the convergence of photophysical observables with respect to the basis size employed, through which we determine the optimal basis for more expensive calculations to be presented in subsequent work. We furthermore evaluate the energetic separation between the optically prepared singlet excited state and the correlated triplet pair state, as well as provide a real-space characterization of the latter, both of which are of key importance in the discussion of fission dynamics. We discuss our results in the context of recent experimental studies.

Exciton-Exciton Annihilation Is Coherently Suppressed in H-Aggregates, but Not in J-Aggregates

We theoretically demonstrate a strong dependence of the annihilation rate between (singlet) excitons on the sign of dipole-dipole couplings between molecules. For molecular H-aggregates, where this sign is positive, the phase relation of the delocalized two-exciton wave functions causes a destructive interference in the annihilation probability. For J-aggregates, where this sign is negative, the interference is constructive instead; as a result, no such coherent suppression of the annihilation rate occurs. As a consequence, room temperature annihilation rates of typical H- and J-aggregates differ by a factor of ∼3, while an order of magnitude difference is found for low-temperature aggregates with a low degree of disorder. These findings, which explain experimental observations, reveal a fundamental principle underlying exciton-exciton annihilation, with major implications for technological devices and experimental studies involving high excitation densities.

Triplet Separation Drives Singlet Fission after Femtosecond Correlated Triplet Pair Production in Rubrene

Singlet fission, a multistep molecular process in which one photon generates two triplet excitons, holds great technological promise. Here, by applying a combination of transient transmittance and two-dimensional electronic spectroscopy with 5 fs laser pulses, we resolve the full set of fission steps before the onset of spin dephasing. In addition to its role as a viable singlet fission material, single-crystalline rubrene is selected because its energetics and transition dipole alignment uniquely allow for the unambiguous identification of the various fission steps through their contributions to distinct spectroscopic features. The measurements reveal that the neighboring correlated triplet pair achieves its maximum population within 20 fs. Subsequent growth of the triplet signal on picosecond time scales is attributable to spatial separation of the triplets, proceeding nonadiabatically through weakly coupled but near-resonant states. As such, we provide evidence in crystalline rubrene for a singlet fission step that, until now, has not been convincingly observed.

Charge Recombination Suppressed by Destructive Quantum Interference in Heterojunction Materials

We show that charge recombination in ordered heterojunctions depends sensitively on the degree of coherent delocalization of charges at the donor-acceptor interface. Depending on the relative sign of the electron and hole transfer integrals, such delocalization can dramatically suppress recombination through destructive quantum interference. This could explain why measured recombination rates are significantly lower than predictions based on Langevin theory for a variety of organic bulk heterojunctions. Moreover, it opens up a design strategy for photovoltaic devices with enhanced efficiencies through coherently suppressed charge recombination.

Vibrational beatings conceal evidence of electronic coherence in the FMO light-harvesting complex

In biological light harvesting, solar energy is captured by photosynthetic antennae for subsequent storage into chemical bonds. The remarkable efficiency reached in transferring the energy between the collection and storage events recently has been attributed to long-lived electronic coherence present in such antennae systems. We present numerical simulations indicating that the spectroscopic transients that supported this hypothesis are not induced by electronic coherence but instead are caused by vibrational (nuclear) motion in the electronic ground state potential. Besides emphasizing the significance of such nuclear modes, our findings stimulate a reconsideration of the role of electronic coherence in promoting energy transfer in natural photosynthesis. Furthermore, they require us to rethink how energy transfer efficiency is reflected in spectral signals.

Mapping the Evolution of Spatial Exciton Coherence through Time-Resolved Fluorescence

Quantum coherence is expected to have a positive effect on the transfer efficiency of excitation energy through photosynthetic aggregates and conjugated polymers, but its significance to the functioning of these molecular assemblies remains largely unknown. We propose a new experimental means to monitor the coherence between distant molecular sites on a time scale relevant to energy transfer. Through numerical calculations, we demonstrate that the range of such spatial coherence continually scales as the 0-0 to 0-1 vibronic peak ratio in time-resolved fluorescence spectroscopy. As such, this observable allows one to monitor the coherent evolution of an excited state, displaying the large coherence length following optical excitation, and the subsequent dephasing over time.

The role of social and psychologic resources in caregiving of cancer patients

BACKGROUND

The role of social support and personality within the cancer caregiving process has remained a relatively unexplored area. The current longitudinal study examines the main and moderating effects on caregiver experiences and caregiver's depression over time of various social and psychologic resources.

METHODS

Newly diagnosed colorectal carcinoma patients and their partners (N = 148) were included and data were obtained at three measurement points: 2 weeks prior to hospital admission and 3 months and 6 months after discharge. The initial and change scores of the caregiver's negative and positive social interactions and personality attributes (mastery, neuroticism, and extraversion) were included to assess their impact on caregiver experiences and depression over time.

RESULTS

The main effects of social and psychologic resources on caregiver experiences were found to be small to absent. With respect to caregiver depression, both initial scores and changes in neuroticism, mastery, and negative social interactions were shown to have substantial main effects over time. Moreover, daily emotional support and mastery modified the relations between caregiver experiences and caregiver depression. Caregivers with a low level of daily emotional support, as well as those with a low score on mastery and who also perceived caregiving in a more negative way were identified as more depressed over time.

CONCLUSIONS

The results of the current study demonstrate the importance of including various social and psychologic resources in studying the cancer caregiving process. It illustrates the distinctive impact of these resources on the depression of caregivers of patients with cancer, and therefore helps healthcare providers understand why some persons adapt better than others to their caregiving role.

Patterns of caregiver experiences among partners of cancer patients

This study describes patterns of caregiving experiences in partners of patients with cancer (N=148) over a 6-month period. Caregiving experiences were assessed by means of the Caregiver Reaction Assessment Scale (CRA), which consists of four negative dimensions and one positive subscale: Disrupted Schedule, Financial Problems, Lack of Family Support, Loss of Physical Strength, and Self-Esteem. Subgroup analyses were performed according to gender, age, and socioeconomic status (SES). Type, size, and direction of changes in caregiving experiences over time were analyzed both at a group level and at an individual level. Patterns of caregiver experiences appeared to vary between the subgroups; women, younger caregivers, and caregivers with a higher SES experienced caregiving more negatively or less positively. The findings illustrate the value of studying inter- and intraindividual patterns across different subgroups, and stress that caregiver experiences should be regarded as a multidimensional concept that includes both negative and positive experiences of caregiving.

Determinants of caregiving experiences and mental health of partners of cancer patients

BACKGROUND

Research regarding informal caregiving showed considerable individual variation in responses to cancer caregiving. The current longitudinal study examined determinants of caregiver outcomes in terms of caregiver experiences at 3 months and caregiver's mental health at 6 months after hospital discharge. It included both negative and positive dimensions of caregiving outcomes.

METHODS

One hundred forty-eight patients with newly diagnosed colorectal carcinoma and their partners were included. Caregiver experiences were assessed by the Caregiver Reaction Assessment Scale, which contains four negative subscales (disrupted schedule, financial problems, lack of family support, and loss of physical strength) and one positive subscale (self-esteem). The mental health of the caregiver was assessed in terms of depression and quality of life. Possible determinants of the caregiver's experiences and mental health were categorized according to characteristics of the caregiver, the patient, and the care situation. Caregiving experiences were studied as a fourth additional category of possible determinants of the caregiver's mental health.

RESULTS

Each domain of the caregiving experience was explained by different factors, with total explained variances ranging between 11-46%. Negative caregiver experiences were associated with a low income, living with only the patient, a distressed relationship, a high level of patient dependency, and a high involvement in caregiving tasks. Caregivers with a low level of education and caregivers of patients with a stoma were able to derive more self-esteem from caregiving. Although caregiving may lead to depression, especially in those experiencing loss of physical strength, caregivers may sustain their quality of life by deriving self-esteem from caregiving.

CONCLUSIONS

It is important that professionals involved in the ongoing care of cancer patients and their families be aware of the increasing demands made on caregivers and the specific problems and uplifts they perceive in caregiving. Professional caregivers are urged to involve informal caregivers with care explicitly and continuously. However, specific attention to those caregivers who live only with the patient, those with a low income, those with a distressed relationship, and those with a high level of patient dependency and care involvement is warranted.

Measuring both negative and positive reactions to giving care to cancer patients: psychometric qualities of the Caregiver Reaction Assessment (CRA)

The Caregiver Reaction Assessment Scale (CRA) is an instrument designed to assess specific aspects of the caregiving situation, including both negative and positive dimensions of caregiving reactions. This paper addresses the psychometric qualities of the CRA in a multicenter study among partners of colorectal cancer patients (n = 181). No problems in feasibility were observed. Five dimensions of caregiver reactions were identified through exploratory factor analysis: the impact of caregiving on disrupted schedule, financial problems, lack of family support, health problems and the impact of caregiving on caregiver's self-esteem. Reliability analyses showed that standardized Cronbach's alpha's varied between 0.62 and 0.83 for the separate subscales, indicating sufficient internal consistencies. Construct validity was supported. The CRA proves to be a feasible, reliable and valid instrument for assessing both negative and positive reactions to caregiving among partners of patients with cancer.

Cancer and caregiving: the impact on the caregiver's health

A diagnosis of cancer affects not only the patient but also their significant others, especially when a lot of care tasks are involved. Some caregivers perceive the care as a burden, while others consider it a challenge. In this article, findings concerning the impact of cancer caregiving on informal caregivers will be described. No consistent results are reported, and little is known about patterns of caregiving changes in relation to the course of the patient's illness. Attention will be given to factors which have been identified as influencing the course and consequences of caregiving. These factors form the basis of a conceptual research model for caregivers of cancer patients. As cancer progresses, care tasks are generated, which can be perceived by the caregiver as either negative (i.e. burden) or positive. Furthermore, these caregiver experiences may lead to negative as well as positive effects on the caregiver's health and these relationships can be assumed to be bidirectional.

A measurement of social support in epidemiological research: the social experiences checklist tested in a general population in The Netherlands

STUDY OBJECTIVE

This study aimed to examine in a general population the psychometric qualities of an instrument designed to measure positive and negative social experiences that had been developed in a clinical setting.

DESIGN

The Netherlands monitoring project on cardiovascular disease risk factors, a large scale population based study (comprising 36,588 men and women aged 20 to 59 years) carried out in three Dutch towns (Amsterdam, Doetinchem, and Maastricht) offered the possibility of testing the strength of this instrument cross sectionally.

MEASUREMENTS AND MAIN RESULTS

The social experiences checklist (SEC) which resulted from a research project on the quality of life of cancer patients was used. The independence of positive and negative experiences was confirmed. The reliability of both the positive and negative experiences dimension was good (Cronbach's alpha = 0.82 and 0.72 respectively). In accordance with the results of a study on cancer patients, the theoretically derived four dimensions in the experience of social support did not seem to be independent. The validity of the SEC was confirmed by Pearson correlations with neuroticism and coping styles. Neuroticism seemed to be negatively correlated with positive social experiences and was positively correlated with negative social experiences. The coping style of seeking information and direct action was positively correlated with positive social experiences. Coping by withdrawal was negatively correlated with negative social experiences. Women and highly educated people seemed to have more positive and fewer negative social experiences than men and people with less education. Younger people had more positive social experiences than older people. The oldest group in the study, those aged 50 to 59, reported fewer negative social experiences than any other age group.

CONCLUSIONS

Similar results were found in a study of cancer patients. This underlines the usefulness of the instrument not only for cancer patients but also in survey research in a general population.

Cancer patients and their network: the meaning of the social network and social interactions for quality of life

A lot of research is carried out on the subject of social relations and quality of life. One should find at least some indication for an association between the social environment and quality of life of cancer patients; will interventions be appropriate and well-considered? But until now, less has been known about the association between the social network of cancer patients and their quality of life. In this study, the way in which the patients' network can effect their quality of life is examined. Two patient groups are distinguished: a group of cancer patients recently treated for their cancer by surgery and a group treated by chemotherapy (n = 108 and n = 109) and these are compared with a disease-free group of cancer patients (n = 192). Although an association between network, social relations and quality of life is found, only a small part of the variation in quality of life can be explained by this social component. It seems that the cancer itself and the cancer treatment mainly affect the patients' quality of life and that the impact of the social environment is less significant.

The distinction between affect and cognition in the quality of life of cancer patients--sensitivity and stability

The distinction between affect and cognition has been put forward to clarify the lack of differences found in studies describing quality of life under deteriorated circumstances, such as serious illness. In the study reported here, cancer patients under treatment (n = 201) were compared with a random sample from the normal population (n = 200). As hypothesized, the affective component of life quality turned out to be more severely impaired than the cognitive component. Besides, it was investigated which factors contribute to the affective and the cognitive component of the quality of life of cancer patients under treatment. In cancer patients affect proved more strongly related to the physical domain. Cognition on the other hand was more strongly related to coping resources, especially personality characteristics like the level of self-esteem. It is concluded that an affective measure of quality of life is more sensitive to change in patients. The stability of life quality is attributed to the rather strong relation the affective and the cognitive component both have to coping resources.

The social experiences of cancer patients under treatment: a comparative study

As part of a larger study on the quality of life of cancer patients under treatment, the positive and negative experiences in social interaction have been examined as compared to those of a control group (nonpatients, n = 201). Two patient groups were included: 109 patients who had recently undergone surgery and 108 patients receiving chemotherapy. The respondents returned a mailed questionnaire. Contrary to the assumptions based on a review from the literature, cancer patients appear to have more positive and fewer negative social experiences than a random sample from the 'normal' population. Even under more severe medical circumstances (a poor prognosis or heavy chemotherapy, a large number of chemotherapy cycles, poor progress after surgery) the poorer the patients, medically speaking, the more help and support they perceive. The results of this study do not support the idea of stigmatization. The personality characteristics, neuroticism and self-esteem are especially important for the having of positive and negative experiences in social interaction. Positive social experiences show a relationship with self-esteem and negative social experiences show a relationship with neuroticism.