1
|
Ramachandran R, Pavithraa S, Meka JK, Rahul KK, Lo JI, Chou SL, Cheng BM, Rajasekhar BN, Bhardwaj A, Mason NJ, Sivaraman B. Vacuum ultraviolet photoabsorption spectra of icy isoprene and its oligomers. Spectrochim Acta A Mol Biomol Spectrosc 2022; 268:120586. [PMID: 34872862 DOI: 10.1016/j.saa.2021.120586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 10/30/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
Isoprene and its oligomers, terpenes, are expected to be present, along with other complex organic molecules in the diverse environments of the ISM and in our solar system. Due to insufficient spectral information of these molecules at low temperature, detection and understanding the importance of these molecules has been rather incomplete. For this purpose, we have carried out the vacuum ultraviolet (VUV) photoabsorption measurements on pure molecular ices of isoprene and a few simple terpenes: limonene, α-pinene and β-pinene by forming icy mantles on cold dust analogs. From these experiments, we report the first low temperature (10 K) VUV spectra of isoprene and its oligomers limonene, α-pinene and β-pinene. VUV photoabsorption spectra of all the molecules reported here reveal similarities in the ice and gas phase as expected, with an exception of isoprene where a prominent red shift is observed in the ice phase absorption. This unqiue property of isoprene along with distinctive absorption at longer wavelengths supports its candidature for detection on icy bodies.
Collapse
Affiliation(s)
| | - S Pavithraa
- Department of Applied Chemistry and Institute of Molecular Sciences, National Chiao Tung University, Hsinchu, Taiwan
| | - J K Meka
- Physical Research Laboratory, Ahmedabad, India
| | - K K Rahul
- Physical Research Laboratory, Ahmedabad, India
| | - J-I Lo
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - S-L Chou
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - B-M Cheng
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - B N Rajasekhar
- Atomic and Molecular Physics Division, Bhabha Atomic Research Center, Mumbai, India
| | | | - N J Mason
- School of Physical Sciences, University of Kent, Canterbury, UK
| | - B Sivaraman
- Physical Research Laboratory, Ahmedabad, India.
| |
Collapse
|
2
|
Rahul KK, Shivakarthik E, Meka JK, Das A, Chandrasekaran V, Rajasekhar BN, Lo JI, Cheng BM, Janardhan P, Bhardwaj A, Mason NJ, Sivaraman B. Residue from vacuum ultraviolet irradiation of benzene ices: Insights into the physical structure of astrophysical dust. Spectrochim Acta A Mol Biomol Spectrosc 2020; 231:117797. [PMID: 31837964 DOI: 10.1016/j.saa.2019.117797] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/12/2019] [Accepted: 11/12/2019] [Indexed: 06/10/2023]
Abstract
We have irradiated benzene ices deposited at 4 K on a cold, interstellar dust analog with vacuum ultraviolet (9 eV) irradiation for periods lasting from several hours to nearly a day, after which the irradiated ice was warmed to room temperature. Vacuum ultraviolet photoabsorption spectra of the aromatic residue left at room temperature were recorded and showed the synthesis of benzene derivatives. The residue was also imaged using an electron microscope and revealed crystals of various sizes and shapes. The result of our experiments suggests such geometrically shaped dust particles may be a key component of interstellar dust.
Collapse
Affiliation(s)
- K K Rahul
- Physical Research Laboratory, Ahmedabad, India
| | | | - J K Meka
- Physical Research Laboratory, Ahmedabad, India
| | - A Das
- Indian Centre for Space Physics, Kolkata, India
| | | | - B N Rajasekhar
- Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai, India
| | - J-I Lo
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - B-M Cheng
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - P Janardhan
- Physical Research Laboratory, Ahmedabad, India
| | - A Bhardwaj
- Physical Research Laboratory, Ahmedabad, India
| | - N J Mason
- School of Physical Sciences, University of Kent, Canterbury, Kent CT2, UK
| | - B Sivaraman
- Physical Research Laboratory, Ahmedabad, India.
| |
Collapse
|
3
|
Rahul KK, Meka JK, Pavithraa S, Gorai P, Das A, Lo JI, Sekhar BNR, Cheng BM, Janardhan P, Bhardwaj A, Mason NJ, Sivaraman B. Infrared attenuation due to phase change from amorphous to crystalline observed in astrochemical propargyl ether ices. Spectrochim Acta A Mol Biomol Spectrosc 2020; 224:117393. [PMID: 31398696 DOI: 10.1016/j.saa.2019.117393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/15/2019] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
Astrochemical ices are known to undergo morphological changes, from amorphous to crystalline, upon warming the ice from lower (10 K) to higher temperatures. Phase changes are mostly identified by the observation of significant changes in the InfraRed (IR) spectrum, where the IR bands that are broad in the amorphous phase are narrower and split when the ice turns crystalline. To-date all the molecules that are studied under astrochemical conditions are observed to follow such a behaviour without significant attenuation in the IR wavelength. However, in this paper we report a new observation when propargyl ether (C3H3OC3H3) is warmed from the amorphous phase, at 10 K, through the phase transition temperature of 170 K, the crystalline ice being found to strongly attenuate IR photons at the mid-IR wavelengths.
Collapse
Affiliation(s)
- K K Rahul
- Physical Research Laboratory, Ahmedabad, India
| | - J K Meka
- Physical Research Laboratory, Ahmedabad, India
| | - S Pavithraa
- Physical Research Laboratory, Ahmedabad, India
| | - P Gorai
- Indian Centre for Space Physics, Kolkata, India
| | - A Das
- Indian Centre for Space Physics, Kolkata, India
| | - J-I Lo
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | | | - B-M Cheng
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - P Janardhan
- Physical Research Laboratory, Ahmedabad, India
| | - A Bhardwaj
- Physical Research Laboratory, Ahmedabad, India
| | | | - B Sivaraman
- Physical Research Laboratory, Ahmedabad, India.
| |
Collapse
|
4
|
Pavithraa S, Lo JI, Cheng BM, Sekhar BNR, Mason NJ, Sivaraman B. Identification of a unique VUV photoabsorption band of carbonic acid for its identification in radiation and thermally processed water-carbon dioxide ices. Spectrochim Acta A Mol Biomol Spectrosc 2019; 215:130-132. [PMID: 30825863 DOI: 10.1016/j.saa.2019.02.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 01/27/2019] [Accepted: 02/16/2019] [Indexed: 06/09/2023]
Abstract
Carbonic acid was synthesized within an ice containing water and carbon dioxide by irradiation of ~9 eV photons. Vacuum UltraViolet (VUV)/UltraViolet (UV) photoabsorption spectra of the irradiated ice revealed absorption features from carbon dioxide, ozone, water, carbon monoxide and oxygen in addition to a band peaking at ~200 nm which is identified to be characteristic of carbonic acid. After thermal processing of the irradiated ice leading to desorption of the lower volatile ices, a pure carbonic acid spectrum is identified starting from 170 K until sublimation above 230 K. Therefore the ~200 nm band in the VUV region corresponding to carbonic acid is proposed to be a unique identifier in mixed ices, rich in water and carbon dioxide typically encountered on planetary and satellite surfaces.
Collapse
Affiliation(s)
- S Pavithraa
- Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India
| | - J-I Lo
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - B-M Cheng
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - B N Raja Sekhar
- B-1, Indus-1, Atomic and molecular Physics division, Bhabha Atomic Research Centre at RRCAT, Indore, India
| | - N J Mason
- School of Physical Sciences, University of Kent, Canterbury, United Kingdom
| | - B Sivaraman
- Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India.
| |
Collapse
|
5
|
Pavithraa S, Lo JI, Rahul K, Raja Sekhar BN, Cheng BM, Mason NJ, Sivaraman B. Vacuum ultraviolet photoabsorption of prime ice analogues of Pluto and Charon. Spectrochim Acta A Mol Biomol Spectrosc 2018; 190:172-176. [PMID: 28922643 DOI: 10.1016/j.saa.2017.08.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 08/23/2017] [Accepted: 08/24/2017] [Indexed: 06/07/2023]
Abstract
Here we present the first Vacuum UltraViolet (VUV) photoabsorption spectra of ice analogues of Pluto and Charon ice mixtures. For Pluto the ice analogue is an icy mixture containing nitrogen (N2), carbon monoxide (CO), methane (CH4) and water (H2O) prepared with a 100:1:1:3 ratio, respectively. Photoabsorption of icy mixtures with and without H2O were recorded and no significant changes in the spectra due to presence of H2O were observed. For Charon a VUV photoabsorption spectra of an ice analogue containing ammonia (NH3) and H2O prepared with a 1:1 ratio was recorded, a spectrum of ammonium hydroxide (NH4OH) was also recorded. These spectra may help to interpret the P-Alice data from New Horizons.
Collapse
Affiliation(s)
- S Pavithraa
- Physical Research Laboratory, Ahmedabad 380 009, India
| | - J-I Lo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - K Rahul
- Physical Research Laboratory, Ahmedabad 380 009, India
| | - B N Raja Sekhar
- Atomic and Molecular Physics Division, BARC at RRCAT, Indore 452 013, India
| | - B-M Cheng
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - N J Mason
- Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
| | - B Sivaraman
- Physical Research Laboratory, Ahmedabad 380 009, India.
| |
Collapse
|
6
|
Pavithraa S, Methikkalam RRJ, Gorai P, Lo JI, Das A, Raja Sekhar BN, Pradeep T, Cheng BM, Mason NJ, Sivaraman B. Qualitative observation of reversible phase change in astrochemical ethanethiol ices using infrared spectroscopy. Spectrochim Acta A Mol Biomol Spectrosc 2017; 178:166-170. [PMID: 28187314 DOI: 10.1016/j.saa.2017.01.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/10/2017] [Accepted: 01/11/2017] [Indexed: 06/06/2023]
Abstract
Here we report the first evidence for a reversible phase change in an ethanethiol ice prepared under astrochemical conditions. InfraRed (IR) spectroscopy was used to monitor the morphology of the ice using the SH stretching vibration, a characteristic vibration of thiol molecules. The deposited sample was able to switch between amorphous and crystalline phases repeatedly under temperature cycles between 10K and 130K with subsequent loss of molecules in every phase change. Such an effect is dependent upon the original thickness of the ice. Further work on quantitative analysis is to be carried out in due course whereas here we are reporting the first results obtained.
Collapse
Affiliation(s)
- S Pavithraa
- Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India
| | - R R J Methikkalam
- Department of Chemistry, Indian Institute of Technology-Madras, Chennai, India
| | - P Gorai
- Indian Centre for Space Physics, Kolkata, India
| | - J-I Lo
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - A Das
- Indian Centre for Space Physics, Kolkata, India
| | - B N Raja Sekhar
- B-1, Indus-1, Atomic Molecular Physics Division, BARC at RRCAT, Indore, India
| | - T Pradeep
- Department of Chemistry, Indian Institute of Technology-Madras, Chennai, India
| | - B-M Cheng
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - N J Mason
- Department of Physical Sciences, The Open University, Milton Keynes, UK
| | - B Sivaraman
- Atomic Molecular and Optical Physics Division, Physical Research Laboratory, Ahmedabad, India.
| |
Collapse
|
7
|
Gessner O, Chrysostom ETH, Lee AMD, Wardlaw DM, Ho ML, Lee SJ, Cheng BM, Zgierski MZ, Chen IC, Shaffer JP, Hayden CC, Stolow A. Non-adiabatic intramolecular and photodissociation dynamics studied by femtosecond time-resolved photoelectron and coincidence imaging spectroscopy. Faraday Discuss 2004; 127:193-212. [PMID: 15471347 DOI: 10.1039/b316742a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
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.
Collapse
Affiliation(s)
- O Gessner
- Steacie Institute for Molecular Sciences, National Research Council, Ottawa ON, Canada
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Cheng BM, Chew EP, Liu CP, Bahou M, Lee YP, Yung YL, Gerstell MF. Photo-induced fractionation of water isotopomers in the Martian atmosphere. Geophys Res Lett 1999; 26:3657-3660. [PMID: 11543402 DOI: 10.1029/1999gl008367] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The history and size of the water reservoirs on early Mars can be constrained using isotopic ratios of deuterium to hydrogen. We present new laboratory measurements of the ultraviolet cross-sections of H2O and its isotopomers, and modeling calculations in support of a photo-induced fractionation effect (PHIFE), that reconciles a discrepancy between past theoretical modeling and recent observations. This supports the hypothesis that Mars had an early warm atmosphere and has lost at least a 50-m global layer of water. Likely applications of PHIFE to other planetary atmospheres are sketched.
Collapse
Affiliation(s)
- B M Cheng
- Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | | | | | | | | | | | | |
Collapse
|
9
|
Cheng BM, Chew EP, Hung WC, Eberhard J, Lee YP. Photoionization studies of sulfur radicals and products of their reactions. J Synchrotron Radiat 1998; 5:1041-1043. [PMID: 15263738 DOI: 10.1107/s0909049597016075] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/1997] [Accepted: 11/10/1997] [Indexed: 05/24/2023]
Abstract
A discharge flow-photoionization mass spectrometric system coupled to a synchrotron is employed to study intermediates and products of sulfur radical reactions related to atmospheric chemistry. Sulfur radicals are generated from reactions of oxygen or chlorine atoms with sulfur compounds in a flow tube. The gaseous reaction products are sampled into the ionization region via a three-stage differential pumping scheme. Photoionization spectra and ionization energies are measured by dispersing synchrotron radiation to ionize the samples. Using this technique, photoionization spectra and ionization energies of HSO, CH(3)SO, C(2)H(5)SO, HSCl, and some secondary reaction products, SSCl, HSSCl, HSSSH, CH(3)SOH and CH(3)SS(O)CH(3), were measured for the first time.
Collapse
Affiliation(s)
- B M Cheng
- Synchrotron Radiation Research Center, No. 1, R&D Road VI, Hsinchu Science-Based Industrial Park, Hsinchu 30077, Taiwan
| | | | | | | | | |
Collapse
|
10
|
Abstract
This paper describes the design and implementation of a constraint-based nurse rostering system using a redundant modeling approach. Nurse rostering is defined as the process of generating timetables for specifying the work shifts of nurses over a given period of time. This process is difficult because the human roster planner has to ensure that every rostering decision made complies with a mixture of hard hospital rules and soft nurse preference rules. Moreover, some nurse shift pre-assignments often break the regularity of wanted (or unwanted) shifts and reduce the choices for other unfilled slots. Soft constraints amount to disjunction, which can be modeled as choices in the search space. This approach, although straightforward, incurs overhead in the search of solution. To reduce search time, we propose redundant modeling, an effective way to increase constraint propagation through cooperations among different models for the same problem. Our problem domain involves around 25 to 28 nurses and 11 shift types. Experiments and pilot testing of the system confirm the effectiveness and efficiency of our method.
Collapse
Affiliation(s)
- B M Cheng
- Department of Computer Science and Engineering, Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | | | | |
Collapse
|