Stable, narrow-linewidth laser system with a broad frequency tunability and a fast switching time

For a Rydberg atom-based sensor to change its sensing frequency, the wavelength of the Rydberg state excitation laser must be altered. The wavelength shifts required can be on the order of 10 nm. A fast-tunable narrow-linewidth laser with broadband tuning capability is required. Here, we present a demonstration of a laser system that can rapidly switch a coupling laser as much as 8 nm in less than 50 μs. The laser system comprises a frequency-stabilized continuous wave laser and an electro-optic frequency comb. A filter enables selection of individual comb lines. A high-speed electro-optic modulator is used to tune the selected comb line to a specific frequency, i.e., an atomic transition. Through Rydberg atom-based sensing experiments, we demonstrate frequency hopping between two Rydberg states and a fast switching time of 400 μs, which we show can be reduced to ∼50 μs with a ping-pong scheme. If updating the RF frequency is not required during frequency hopping, a 200 ns switching time can be achieved. These results showcase the potential of the laser system for advanced Rydberg atom-based radio frequency sensing applications, like communications and radar.

Ultracold Rydberg molecules

Ultracold molecules formed from association of a single Rydberg atom with surrounding atoms or molecules and those from double Rydberg excitations are discussed in this review. Ultralong-range Rydberg molecules possess a novel molecular bond resulting from scattering of the Rydberg electron from the perturber atoms or molecules. The strong interactions between Rydberg atoms in ultracold gases may lead to formation of macroscopic Rydberg macrodimers. The exquisite control over the properties of the Rydberg electron means that interesting and unusual few-body and quantum many-body features can be realized in such systems.

Rydberg molecules have been extensively studied both theoretically and experimentally. Here the authors review the recent developments in the study of various types of Rydberg molecules and their potential for future applications in spectroscopy, sensing and quantum information.

Electric Field Cancellation on Quartz by Rb Adsorbate-Induced Negative Electron Affinity

We investigate the (0001) surface of single crystal quartz with a submonolayer of Rb adsorbates. Using Rydberg atom electromagnetically induced transparency, we investigate the electric fields resulting from Rb adsorbed on the quartz surface, and measure the activation energy of the Rb adsorbates. We show that the adsorbed Rb induces negative electron affinity (NEA) on the quartz surface. The NEA surface allows low energy electrons to bind to the surface and cancel the electric field from the Rb adsorbates. Our results will be important for integrating Rydberg atoms into hybrid quantum systems, as fundamental probes of atom-surface interactions, and for studies of 2D electron gases bound to surfaces.

Strongly Correlated Growth of Rydberg Aggregates in a Vapor Cell

The observation of strongly interacting many-body phenomena in atomic gases typically requires ultracold samples. Here we show that the strong interaction potentials between Rydberg atoms enable the observation of many-body effects in an atomic vapor, even at room temperature. We excite Rydberg atoms in cesium vapor and observe in real time an out-of-equilibrium excitation dynamics that is consistent with an aggregation mechanism. The experimental observations show qualitative and quantitative agreement with a microscopic theoretical model. Numerical simulations reveal that the strongly correlated growth of the emerging aggregates is reminiscent of soft-matter type systems.

Molecular physics. Production of trilobite Rydberg molecule dimers with kilo-Debye permanent electric dipole moments

Permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions, and realization of strongly correlated many-body quantum systems. However, large molecular permanent electric dipole moments are challenging to realize experimentally. We report the observation of ultralong-range Rydberg molecules with bond lengths of ~100 nanometers and kilo-Debye permanent electric dipole moments that form when an ultracold ground-state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit. The electronic character of this hybrid class of "trilobite" molecules is dominated by degenerate Rydberg manifolds, making them difficult to produce by conventional photoassociation. We used detailed coupled-channel calculations to reproduce their properties quantitatively. Our findings may lead to progress in ultracold chemistry and strongly correlated many-body physics.

Subwavelength microwave electric-field imaging using Rydberg atoms inside atomic vapor cells

We have recently shown [Nat. Phys.8, 819 (2012)] that Alkali atoms contained in a vapor cell can serve as a highly accurate standard for microwave (MW) electric field strength as well as polarization. Here we show for the first time that Rydberg atom electromagnetically induced transparency can be used to image MW electric fields with unprecedented precision. The spatial resolution of the method is far into the subwavelength regime ∼λ/650 or 66 μm at 6.9 GHz. The electric field resolutions are similar to those we have already demonstrated ∼50  μV cm(-1). Our experimental results agree with finite element calculations of test electric-field patterns.

Atom-based vector microwave electrometry using rubidium Rydberg atoms in a vapor cell

It is clearly important to pursue atomic standards for quantities like electromagnetic fields, time, length, and gravity. We have recently shown using Rydberg states that Rb atoms in a vapor cell can serve as a practical, compact standard for microwave electric field strength. Here we demonstrate for the first time that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg-atom electromagnetically induced transparency. We describe the measurements necessary to obtain an arbitrary microwave electric field polarization at a resolution of 0.5°. We compare the experiments to theory and find them to be in excellent agreement.

Observation of blueshifted ultralong-range Cs2 Rydberg molecules

We observe ultralong-range blueshifted Cs(2) molecular states near ns(1/2) Rydberg states in an optical dipole trap, where 31≤n≤34. The accidental near degeneracy of (n-4)l and ns Rydberg states for l>2 in Cs, due to the small fractional ns quantum defect, leads to nonadiabatic coupling among these states, producing potential wells above the ns thresholds. Two important consequences of admixing high angular momentum states with ns states are the formation of large permanent dipole moments, ~15-100 Debye, and accessibility of these states via two-photon association. The observed states are in excellent agreement with theory.

Rydberg trimers and excited dimers bound by internal quantum reflection

In a combined experimental and theoretical effort we report on two novel types of ultracold long-range Rydberg molecules. First, we demonstrate the creation of triatomic molecules of one Rydberg atom and two ground-state atoms in a single-step photoassociation. Second, we assign a series of excited dimer states that are bound by a so far unexplored mechanism based on internal quantum reflection at a steep potential drop. The properties of the Rydberg molecules identified in this work qualify them as prototypes for a new type of chemistry at ultracold temperatures.

Electric field effects in the excitation of cold Rydberg-atom pairs

In this work, we study the role of the ac Stark effects on the excitation of nS1/2 cold Rydberg atoms produced in a rubidium magneto-optical trap. We have observed an atomic population in the nP3/2 state after excitation of nS1/2 for 29<or=n<or=37. Such an observation is normally attributed to binary collisions; however, the interaction between Rb nS1/2 atoms is repulsive. To explain our results, the dipole-dipole interaction and ac Stark shifts from the excitation laser must be considered. We find that the Rydberg-atom-pair state asymptotically correlating to nP3/2+(n-1)P3/2 is excited directly.

Femtosecond Multidimensional Imaging of a Molecular Dissociation

The coupled electronic and vibrational motions governing chemical processes are best viewed from the molecule's point of view-the molecular frame. Measurements made in the laboratory frame often conceal information because of the random orientations the molecule can take. We used a combination of time-resolved photoelectron spectroscopy, multidimensional coincidence imaging spectroscopy, and ab initio computation to trace a complete reactant-to-product pathway-the photodissociation of the nitric oxide dimer-from the molecule's point of view, on the femtosecond time scale. This method revealed an elusive photochemical process involving intermediate electronic configurations.

Non-adiabatic intramolecular and photodissociation dynamics studied by femtosecond time-resolved photoelectron and coincidence imaging spectroscopy

Time-resolved photoelectron spectroscopy (TRPES) is emerging as a useful tool for the study of non-adiabatic dynamics in isolated polyatomic molecules and clusters due to its sensitivity to both electronic and vibrational dynamics. A powerful extension of TRPES, coincidence imaging spectroscopy (CIS), based upon femtosecond time-resolved 3D momentum vector imaging of both photoions and photoelectrons in coincidence, is a new technique for the study of complex dissociative processes. Here we show how these spectroscopies can be used to study both non-adiabatic intramolecular and photodissociation dynamics in polyatomic molecules. Intramolecular dynamics in the alpha, beta-enones acrolein, crotonaldehyde and methyl vinyl ketone are studied using both TRPES and laser-induced fluorescence of HCO(X) product yields. The location of the methyl group is seen to have very dramatic effects on the relative electronic relaxation rates and the HCO(X) yield. Applying both TRPES and CIS to the 200 nm and 209 nm photodissociation of the nitric oxide dimer, (NO)2, we observe the fs time-scale evolution of the excited parent neutral via its photoelectron spectrum and the emergence of the NO(A) photofragment including its energy and angular distributions.

Towards disentangling coupled electronic-vibrational dynamics in ultrafast non-adiabatic processes

Femtosecond time-resolved photoelectron spectroscopy is emerging as a new technique for investigating polyatomic excited state dynamics. Due to the sensitivity of photoelectron spectroscopy to both electronic configurations and vibrational dynamics, it is well suited to the study of non-adiabatic processes such as internal conversion, which often occur on sub-picosecond time scales. We discuss the technical requirements for such experiments, including lasers systems, energy- and angle-resolved photoelectron spectrometers and new detectors for coincidence experiments. We present a few examples of these methods applied to problems in diatomic wavepacket dynamics and ultrafast non-adiabatic processes in polyatomic molecules.

The use of expandable metal stents to facilitate extubation in patients with large airway obstruction

OBJECTIVE

To determine the clinical utility of placing airway stents to facilitate weaning in ventilator-dependent patients with large airway obstruction.

METHODS

A chart review of mechanically ventilated patients who received expandable metal airway stents to attempt a facilitation of weaning.

RESULTS

Eight patients, 3 women and 5 men, ranging in age from 37 to 82 years, had respiratory failure associated with large airway obstruction and underwent flexible bronchofluoroscopic placement of 12 expandable metal stents (7 Wallstents [Schneider; Minneapolis, MN], 2 Palmaz [Johnson & Johnson; Warren, NJ], and 3 Ultraflex [Microinvasive; Natick, MA]). Six had respiratory failure that was secondary to malignant airway disease, and two had benign airway disease. Seven patients with tracheal or mainstem bronchial obstruction were weaned from the ventilator within 0 to 11 days of stent placement after having previously required mechanical ventilation from 2 to 52 days. There were no associated complications. Following prolonged attempts at weaning, one patient with lobar bronchus obstruction died after mechanical ventilation was withdrawn.

CONCLUSIONS

Expandable metal airway stents may be safely deployed in mechanically ventilated patients and can facilitate weaning from the mechanical ventilator. Mechanically ventilated patients with tracheal and mainstem bronchus obstruction are the best candidates for deployment of expandable airway stents to facilitate weaning.

Massive hemoptysis as the presenting manifestation in a child with histoplasmosis

A previously healthy and asymptomatic 7-year-old white boy presented with a history of two episodes of hemoptysis productive of bright red blood in the 5 days preceding admission. After admission he developed massive hemoptysis that, on bronchoscopy, was noted to be emanating from the right lower lobe. An emergency right lower lobe resection was done. Pathological examination revealed hilar adenopathy and peripheral lesions with caseating granulomas containing yeast, morphologically consistent with Histoplasma capsulatum.