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Muller G, Catani KJ, Scholz MS, Jacovella U, Bartlett NI, Bieske EJ. Electronic Spectra of Diacetylene Cations (HC 4H +) Tagged with Ar and N 2. J Phys Chem A 2019; 123:7228-7236. [DOI: 10.1021/acs.jpca.9b05996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Giel Muller
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Katherine J. Catani
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Michael S. Scholz
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Ugo Jacovella
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Nastasia I. Bartlett
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Evan J. Bieske
- School of Chemistry, University of Melbourne, Parkville, Victoria 3010, Australia
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2
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Jacovella U, Merkt F. Spin-orbit interaction and Renner-Teller effect in HCCCCH + studied by high-resolution photoelectron spectroscopy. Phys Chem Chem Phys 2018; 19:23524-23531. [PMID: 28829462 DOI: 10.1039/c7cp04759b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photoelectron spectra of the X+ 2Πg ← X 1Σ photoionizing transition of diacetylene (HCCCCH) and d2-diacetylene (DCCCCD) have been recorded at high resolution using the technique of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy. The partially resolved rotational structure of the origin band of the spectra of HCCCCH and DCCCCD has enabled the determination of the adiabatic ionization energies of HCCCCH [Ead = 82072.2(5) cm-1] and DCCCCD [Ead = 82090.0(10) cm-1] and of the spin-orbit coupling constant [A = -31.1(4) cm-1] of the ground vibronic state of HCCCCH+, which is smaller than the value of -33.3 cm-1 commonly used since the work of Callomon (J. H. Callomon, Can. J. Phys., 1956, 34, 1046). Several excited vibrational levels of HCCCCH+ and DCCCCD+, including some affected by the Renner-Teller effect and Fermi interactions, have been observed and the fundamental wavenumber of the mode ν9 has been determined in both HCCCCH+ (200.0(10) cm-1) and DCCCCD+ (192.6(20) cm-1). Possible assignments for several of these levels are discussed and deficiencies in the current understanding of the energy-level structure of the radical cation of diacetylene are pointed at.
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Affiliation(s)
- U Jacovella
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich, Switzerland.
| | - F Merkt
- Laboratorium für Physikalische Chemie, ETH Zürich, CH-8093 Zurich, Switzerland.
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Agúndez M, Cernicharo J, Quintana-Lacaci G, Castro-Carrizo A, Velilla Prieto L, Marcelino N, Guélin M, Joblin C, Martín-Gago JA, Gottlieb CA, Patel NA, McCarthy MC. The growth of carbon chains in IRC +10216 mapped with ALMA. ASTRONOMY AND ASTROPHYSICS 2017; 601:A4. [PMID: 28469283 PMCID: PMC5405872 DOI: 10.1051/0004-6361/201630274] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Linear carbon chains are common in various types of astronomical molecular sources. Possible formation mechanisms involve both bottom-up and top-down routes. We have carried out a combined observational and modeling study of the formation of carbon chains in the C-star envelope IRC +10216, where the polymerization of acetylene and hydrogen cyanide induced by ultraviolet photons can drive the formation of linear carbon chains of increasing length. We have used ALMA to map the emission of λ 3 mm rotational lines of the hydrocarbon radicals C2H, C4H, and C6H, and the CN-containing species CN, C3N, HC3N, and HC5N with an angular resolution of ~1″. The spatial distribution of all these species is a hollow, 5-10″ wide, spherical shell located at a radius of 10-20″ from the star, with no appreciable emission close to the star. Our observations resolve the broad shell of carbon chains into thinner sub-shells which are 1-2″ wide and not fully concentric, indicating that the mass loss process has been discontinuous and not fully isotropic. The radial distributions of the species mapped reveal subtle differences: while the hydrocarbon radicals have very similar radial distributions, the CN-containing species show more diverse distributions, with HC3N appearing earlier in the expansion and the radical CN extending later than the rest of the species. The observed morphology can be rationalized by a chemical model in which the growth of polyynes is mainly produced by rapid gas-phase chemical reactions of C2H and C4H radicals with unsaturated hydrocarbons, while cyanopolyynes are mainly formed from polyynes in gas-phase reactions with CN and C3N radicals.
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Affiliation(s)
- M Agúndez
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - J Cernicharo
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - G Quintana-Lacaci
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - A Castro-Carrizo
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
| | - L Velilla Prieto
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - N Marcelino
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - M Guélin
- Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St. Martin d'Héres, France
| | - C Joblin
- Université de Toulouse, UPS-OMS, IRAP, 31000 Toulouse, France
- CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
| | - J A Martín-Gago
- Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain
| | - C A Gottlieb
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - N A Patel
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - M C McCarthy
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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Wang H, Yu S, Su S, Dai D, Yuan K, Yang X. Photodissociation Dynamics of Diacetylene Rydberg States. J Phys Chem A 2015; 119:11313-9. [PMID: 26492566 DOI: 10.1021/acs.jpca.5b08865] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The state-selective photodissociation of diacetylene (C4H2) was studied in the wavelength range of 127.5-164.4 nm by high-resolution Rydberg H atom time-of-flight spectroscopy measurements. In the wavelength region, two Rydberg series nR and nR' were state-selectively excited using tunable vacuum-ultraviolet laser radiation. In all photolysis wavelengths, two decay channels with different dissociation dynamics were observed. In one channel, the characteristic and isotropic translational energy distributions with a peak around 1800 cm(-1) can be found, suggesting statistical dissociation through internal conversion (IC) from the Rydberg state to the ground state and then dissociation on the ground-state surface. In contrast to this, in the second channel, nonstatistical and anisotropic translational energy distributions were observed, possibly through IC to the excited repulsive state. The vibrational progressions of C4H (A(2)Π) products have also been observed and assigned to the CCC bend and C≡C stretch progressions in the second channel at 3R Rydberg states.
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Affiliation(s)
- Hongzhen Wang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
| | - Shengrui Yu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
| | - Shu Su
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
| | - Dongxu Dai
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
| | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, China
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Mayer R, Lin L, Fager M, Douglas D, McDonough J, Carabe A. Proposed linear energy transfer areal detector for protons using radiochromic film. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:044301. [PMID: 25933872 DOI: 10.1063/1.4917418] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Radiation therapy depends on predictably and reliably delivering dose to tumors and sparing normal tissues. Protons with kinetic energy of a few hundred MeV can selectively deposit dose to deep seated tumors without an exit dose, unlike x-rays. The better dose distribution is attributed to a phenomenon known as the Bragg peak. The Bragg peak is due to relatively high energy deposition within a given distance or high Linear Energy Transfer (LET). In addition, biological response to radiation depends on the dose, dose rate, and localized energy deposition patterns or LET. At present, the LET can only be measured at a given fixed point and the LET spatial distribution can only be inferred from calculations. The goal of this study is to develop and test a method to measure LET over extended areas. Traditionally, radiochromic films are used to measure dose distribution but not for LET distribution. We report the first use of these films for measuring the spatial distribution of the LET deposited by protons. The radiochromic film sensitivity diminishes for large LET. A mathematical model correlating the film sensitivity and LET is presented to justify relating LET and radiochromic film relative sensitivity. Protons were directed parallel to radiochromic film sandwiched between solid water slabs. This study proposes the scaled-normalized difference (SND) between the Treatment Planning system (TPS) and measured dose as the metric describing the LET. The SND is correlated with a Monte Carlo (MC) calculation of the LET spatial distribution for a large range of SNDs. A polynomial fit between the SND and MC LET is generated for protons having a single range of 20 cm with narrow Bragg peak. Coefficients from these fitted polynomial fits were applied to measured proton dose distributions with a variety of ranges. An identical procedure was applied to the protons deposited from Spread Out Bragg Peak and modulated by 5 cm. Gamma analysis is a method for comparing the calculated LET with the LET measured using radiochromic film at the pixel level over extended areas. Failure rates using gamma analysis are calculated for areas in the dose distribution using parameters of 25% of MC LET and 3 mm. The processed dose distributions find 5%-10% failure rates for the narrow 12.5 and 15 cm proton ranges and 10%-15% for proton ranges of 15, 17.5, and 20 cm and modulated by 5 cm. It is found through gamma analysis that the measured proton energy deposition in radiochromic film and TPS can be used to determine LET. This modified film dosimetry provides an experimental areal LET measurement that can verify MC calculations, support LET point measurements, possibly enhance biologically based proton treatment planning, and determine the polymerization process within the radiochromic film.
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Affiliation(s)
- Rulon Mayer
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, Maryland 20817, USA
| | - Liyong Lin
- Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA
| | - Marcus Fager
- Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA
| | - Dan Douglas
- Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA
| | - James McDonough
- Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA
| | - Alejandro Carabe
- Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA
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Leach S, Garcia GA, Mahjoub A, Bénilan Y, Fray N, Gazeau MC, Gaie-Levrel F, Champion N, Schwell M. Ionization photophysics and spectroscopy of cyanoacetylene. J Chem Phys 2014; 140:174305. [PMID: 24811639 DOI: 10.1063/1.4871298] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photoionization of cyanoacetylene was studied using synchrotron radiation over the non-dissociative ionization excitation range 11-15.6 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of cyanoacetylene was measured as 11.573 ± 0.010 eV. A detailed analysis of photoelectron spectra of HC3N involves new aspects and new assignments of the vibrational components to excitation of the A(2)Σ(+) and B(2)Π states of the cation. Some of the structured autoionization features observed in the 11.94 to 15.5 eV region of the total ion yield (TIY) spectrum were assigned to two Rydberg series converging to the B(2)Π state of HC3N(+). A number of the measured TIY features are suggested to be vibrational components of Rydberg series converging to the C(2)Σ(+) state of HC3N(+) at ≈17.6 eV and others to valence shell transitions of cyanoacetylene in the 11.6-15 eV region. The results of quantum chemical calculations of the cation electronic state geometries, vibrational frequencies and energies, as well as of the C-H dissociation potential energy profiles of the ground and electronic excited states of the ion, are compared with experimental observations. Ionization quantum yields are evaluated and discussed and the problem of adequate calibration of photoionization cross-sections is raised.
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Affiliation(s)
- Sydney Leach
- LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France
| | - Gustavo A Garcia
- Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France
| | - Ahmed Mahjoub
- LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France
| | - Yves Bénilan
- LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France
| | - Nicolas Fray
- Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France
| | - Marie-Claire Gazeau
- LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France
| | - François Gaie-Levrel
- Synchrotron SOLEIL, L'Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex, France
| | - Norbert Champion
- LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France
| | - Martin Schwell
- LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France
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Leach S, Schwell M, Garcia GA, Bénilan Y, Fray N, Gazeau MC, Gaie-Levrel F, Champion N, Guillemin JC. Ionization photophysics and spectroscopy of dicyanoacetylene. J Chem Phys 2013; 139:184304. [PMID: 24320271 DOI: 10.1063/1.4826467] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photoionization of dicyanoacetylene was studied using synchrotron radiation over the excitation range 8-25 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and detailed spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of dicyanoacetylene was measured as 11.80 ± 0.01 eV. A detailed analysis of the cation spectroscopy involves new aspects and new assignments of the vibrational components to excitation of the quasi-degenerate A(2)Πg, B(2)Σg(+) states as well as the C(2)Σu(+) and D(2)Πu states of the cation. Some of the structured autoionization features observed in the 12.4-15 eV region of the total ion yield spectrum were assigned to vibrational components of valence shell transitions and to two previously unknown Rydberg series converging to the D(2)Πu state of C4N2(+). The appearance energies of the fragment ions C4N(+), C3N(+), C4(+), C2N(+), and C2(+) were measured and their heats of formation were determined and compared with existing literature values. Thermochemical calculations of the appearance potentials of these and other weaker ions were used to infer aspects of dissociative ionization pathways.
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Affiliation(s)
- Sydney Leach
- LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon, France
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