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Lin KC, Muthiah B, Chang HP, Kasai T, Chang YP. Halogen-related photodissociation in atmosphere: characterisation of atomic halogen, molecular halogen, and hydrogen halide. INT REV PHYS CHEM 2020. [DOI: 10.1080/0144235x.2020.1822590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- King-Chuen Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
| | | | - Hsiu-Pu Chang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Toshio Kasai
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
- Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Yuan-Pin Chang
- Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan
- Aerosol Science Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan
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Franklin-Mergarejo R, Rubayo-Soneira J, Halberstadt N, Janda KC, Apkarian VA. A theoretical simulation of the resonant Raman spectroscopy of the H2O⋯Cl2 and H2O⋯Br2 halogen-bonded complexes. J Chem Phys 2016; 144:054307. [DOI: 10.1063/1.4940778] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ricardo Franklin-Mergarejo
- Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, F-31062 Toulouse, France
- CNRS, UMR 5589, F-31062 Toulouse, France
- InSTEC, Quinta de los Molinos, Ave. Salvador Allende y Luaces, Plaza, Ciudad Habana, Cuba
| | - Jesús Rubayo-Soneira
- InSTEC, Quinta de los Molinos, Ave. Salvador Allende y Luaces, Plaza, Ciudad Habana, Cuba
| | - Nadine Halberstadt
- Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, F-31062 Toulouse, France
- CNRS, UMR 5589, F-31062 Toulouse, France
| | - Kenneth C. Janda
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, USA
| | - V. Ara Apkarian
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, USA
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Lin KC, Tsai PY. Molecular halogen elimination from halogen-containing compounds in the atmosphere. Phys Chem Chem Phys 2014; 16:7184-98. [PMID: 24622955 DOI: 10.1039/c3cp54828g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Atmospheric halogen chemistry has drawn much attention, because the halogen atom (X) playing a catalytic role may cause severe stratospheric ozone depletion. Atomic X elimination from X-containing hydrocarbons is recognized as the major primary dissociation process upon UV-light irradiation, whereas direct elimination of the X2 product has been seldom discussed or remained a controversial issue. This account is intended to review the detection of X2 primary products using cavity ring-down absorption spectroscopy in the photolysis at 248 nm of a variety of X-containing compounds, focusing on bromomethanes (CH2Br2, CF2Br2, CHBr2Cl, and CHBr3), dibromoethanes (1,1-C2H4Br2 and 1,2-C2H4Br2) and dibromoethylenes (1,1-C2H2Br2 and 1,2-C2H2Br2), diiodomethane (CH2I2), thionyl chloride (SOCl2), and sulfuryl chloride (SO2Cl2), along with a brief discussion on acyl bromides (BrCOCOBr and CH2BrCOBr). The optical spectra, quantum yields, and vibrational population distributions of the X2 fragments have been characterized, especially for Br2 and I2. With the aid of ab initio calculations of potential energies and rate constants, the detailed photodissociation mechanisms may be comprehended. Such studies are fundamentally important to gain insight into the dissociation dynamics and may also practically help to assess the halogen-related environmental variation.
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Affiliation(s)
- King-Chuen Lin
- Department of Chemistry, National Taiwan University, Taipei, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
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Gomes JDS, Gargano R, Martins JBL, M de Macedo LG. Relativistic four-component potential energy curves for the lowest 23 covalent states of molecular bromine (Br2). J Phys Chem A 2014; 118:5818-22. [PMID: 24779448 DOI: 10.1021/jp4114283] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The covalent excited states and ground state of the Br2 molecule has been investigated by using four-component relativistic COSCI and MRCISD methods. These methods were performed for all covalent states in the representation Ω((±)). Calculated potential energy curves (PECs) were obtained at the four-component COSCI level, and spectroscopic constants (R(e), D(e), D0, ω(e), ω(e)x(e), ω(e)y(e), B(e), α(e), γ(e), Te, Dv) for bounded states are reported. The vertical excitations for all covalent states are reported at COSCI, MRCISD, and MRCISD+Q levels. We also present spectroscopic constants for two weakly bounded states (A':(1)2u and B':(1)0(-)u) not yet reported in the literature, as well as accurate analytical curves for all five relativistic molecular bounded sates [the ground state X:0 g(+) and the excited states A:(1)1(u), B:(1)0(u)(+), C:(2)1(u), and B':(1)0(u)(-)] found in this work.
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Affiliation(s)
- José da Silva Gomes
- Faculdade de Biotecnologia, Instituto de Ciências Biológicas, Universidade Federal do Pará (UFPA) , Belém, Pará 66075-110, Brazil
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Fan H, Tsai PY, Lin KC, Lin CW, Yan CY, Yang SW, Chang AHH. Molecular elimination of Br2 in photodissociation of CH2BrC(O)Br at 248 nm using cavity ring-down absorption spectroscopy. J Chem Phys 2012; 137:214304. [DOI: 10.1063/1.4767346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Tellinghuisen J. Analysis of the visible absorption spectrum of I2 in inert solvents using a physical model. J Phys Chem A 2012; 116:391-8. [PMID: 22128887 DOI: 10.1021/jp211215v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Absorption spectra of I(2) dissolved in n-heptane and CCl(4) are analyzed with a quantum gas-phase model, in which spectra at four temperatures between 15° and 50 °C are least-squares fitted by bound-free spectral simulations to obtain estimates of the excited-state potential energy curves and transition moment functions for the three component bands--A ← X, B ← X, and C ← X. Compared with a phenomenological band-fitting model used previously on these spectra, the physical model (1) is better statistically, and (2) yields component bands with less variability. The results support the earlier tentative conclusion that most of the ~20% gain in intensity in solution is attributable to the C ← X transition. The T-dependent changes in the spectrum are accounted for by potential energy shifts that are linear in T and negative (giving red shifts in the spectra) and about twice as large for CCl(4) as for heptane. The derived upper potentials resemble those in the gas phase, with one major exception: In the statistically best convergence mode, the A potential is much lower and steeper, with a strongly varying transition moment function. This observation leads to the realization that two markedly different potential curves can give nearly identical absorption spectra.
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Affiliation(s)
- Joel Tellinghuisen
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
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Wu CC, Lin HC, Chang YB, Tsai PY, Yeh YY, Fan H, Lin KC, Francisco JS. Br2 molecular elimination in photolysis of (COBr)2 at 248 nm by using cavity ring-down absorption spectroscopy: A photodissociation channel being ignored. J Chem Phys 2011; 135:234308. [DOI: 10.1063/1.3664782] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Tellinghuisen J. Least-squares analysis of overlapped bound-free absorption spectra and predissociation data in diatomics: the C(1Πu) state of I2. J Chem Phys 2011; 135:054301. [PMID: 21823694 DOI: 10.1063/1.3616039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Absorption spectra are recorded at low resolution but high quantitative precision for I(2) vapor at 35 °C and 64 °C. These and literature spectra are analyzed by least-squares quantum spectral simulation of the overlapped A ← X, B ← X, and C((1)Π(u)) ← X transitions, with the aid of a pseudocontinuum model for the discrete regions of the A ← X and B ← X spectra. The analysis yields improved descriptions of the small-R regions of the A- and B-state potentials, which are known precisely at larger R from discrete spectroscopy. The C potential is determined at small R from its C ← X absorption, at intermediate R from literature data for B → C predissociation, and at large R from its known van der Waals well. The estimates of the electronic transition moment function ∣μ(e)(R)∣ for the B-X transition expand upon precise results from a recent determination by a different method. For the C-X and A-X transitions, the R-dependence of the transition moment functions resembles that found previously for these systems in Br(2). Of the spectroscopic properties, the C ← X spectrum is most altered from the previous analysis, being now ∼20% weaker. For B → C predissociation, no derived C potential has yielded computed rates in adequate statistical agreement with the analyzed experimental data.
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Affiliation(s)
- Joel Tellinghuisen
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
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Tellinghuisen J. Intensity analysis of overlapped discrete and continuous absorption by spectral simulation: The electronic transition moment for the B–X system in I2. J Chem Phys 2011; 134:084301. [DOI: 10.1063/1.3555623] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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Franklin-Mergarejo R, Rubayo-Soneira J, Halberstadt N, Ayed T, Bernal-Uruchurtu MI, Hernández-Lamoneda R, Janda KC. Large Shift and Small Broadening of Br2 Valence Band upon Dimer Formation with H2O: An Ab Initio Study. J Phys Chem A 2011; 115:5983-91. [DOI: 10.1021/jp110389z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ricardo Franklin-Mergarejo
- Instituto Superior de Tecnologías y Ciencias Aplicadas, Ave. Salvador Allende y Luaces, Quinta de los Molinos, Plaza, Habana 10600, Aptdo. Postal 6163, Ciudad Habana, Cuba
- Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, F-31062 Toulouse, France
- CNRS, UMR 5589, F-31062 Toulouse, France
| | - Jesus Rubayo-Soneira
- Instituto Superior de Tecnologías y Ciencias Aplicadas, Ave. Salvador Allende y Luaces, Quinta de los Molinos, Plaza, Habana 10600, Aptdo. Postal 6163, Ciudad Habana, Cuba
| | - Nadine Halberstadt
- Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, F-31062 Toulouse, France
- CNRS, UMR 5589, F-31062 Toulouse, France
| | - Tahra Ayed
- Centro de Investigaciones Químicas, UAEM, Cuernavaca, Mor. 62209, México
| | | | | | - Kenneth C. Janda
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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Sanz-Sanz C, Roncero O, Hernández-Lamoneda R, Pio JM, Taylor MA, Janda KC. Communications: A model study on the electronic predissociation of the NeBr(2) van der Waals complex. J Chem Phys 2010; 132:221103. [PMID: 20550382 DOI: 10.1063/1.3429940] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recently, the predissociation lifetimes of the NeBr(2)(B) complex for different initial vibrational excitation (10<or=v(')<or=20) have been measured using time-resolved optical pump-probe spectroscopy [Taylor et al., J. Chem. Phys., 132, 104309 (2010)]. In the vibrational interval studied, the vibrational predissociation (VP) proceeds by the transfer of a single vibrational quantum and the lifetimes are expected to decrease smoothly with increasing v('), as predicted by the energy gap law. However, the experimental lifetimes show strong oscillations with v('), which were attributed to the occurrence of electronic predissociation into two possible dissociative electronic states of Br(2)(1(g),2(g)), based on a Franck-Condon spectator model. In this work we reproduce the experimental findings by performing full three-dimensional wave packet calculations for the competition of vibrational and electronic predissociation, including the B(0(u) (+)), 2(g), and C(1(u)) electronic states. Model potential energy surfaces were used based on previous theoretical simulations of the VP dynamics on the B state and on ab initio calculations on the NeCl(2) related system. Thus, only two parameters, the strength of the electronic couplings, are fit to achieve the excellent theoretical/experimental agreement.
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Taylor MA, Pio JM, van der Veer WE, Janda KC. Competition between electronic and vibrational predissociation dynamics of the HeBr2 and NeBr2 van der Waals molecules. J Chem Phys 2010; 132:104309. [DOI: 10.1063/1.3353954] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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Branigan ET, van Staveren MN, Apkarian VA. Solidlike coherent vibronic dynamics in a room temperature liquid: Resonant Raman and absorption spectroscopy of liquid bromine. J Chem Phys 2010; 132:044503. [DOI: 10.1063/1.3291610] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Lee PC, Tsai PY, Hsiao MK, Lin KC, Huang CH, Chang AHH. Probing the Ignored Elimination Channel of Br2in the 248 nm Photodissociation of 1,1-Dibromoethylene by Cavity Ring-Down Absorption Spectroscopy. Chemphyschem 2009; 10:672-9. [DOI: 10.1002/cphc.200800665] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Tellinghuisen J. Equilibrium Constants from Spectrophotometric Data: Dimer Formation in Gaseous Br2. J Phys Chem A 2008; 112:5902-7. [DOI: 10.1021/jp8020358] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Joel Tellinghuisen
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235
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Chang YP, Lee PC, Lin KC, Huang CH, Sun BJ, Chang AHH. Photodissociation of 1,2-Dibromoethylene at 248 nm: Br2 Molecular Elimination Probed by Cavity Ring-Down Absorption Spectroscopy. Chemphyschem 2008; 9:1137-45. [DOI: 10.1002/cphc.200700861] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pio JM, van der Veer WE, Bieler CR, Janda KC. Product state resolved excitation spectroscopy of He–, Ne–, and Ar–Br2 linear isomers: Experiment and theory. J Chem Phys 2008; 128:134311. [DOI: 10.1063/1.2885047] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Han YC, Yuan KJ, Hu WH, Yan TM, Cong SL. Steering dissociation of Br2 molecules with two femtosecond pulses via wave packet interference. J Chem Phys 2008; 128:134303. [DOI: 10.1063/1.2844792] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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Ibrahim H, Gühr M, Schwentner N. Valence transitions of Br2 in Ar matrices: interaction with the lattice and predissociation. J Chem Phys 2008; 128:064504. [PMID: 18282053 DOI: 10.1063/1.2826341] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fluorescence spectra from v(')=0 of the B, A and A(') states of Br(2)Ar are presented for excitation wavelengths from 630 to 540 nm with high resolution, to evaluate isotopic splittings in emission and absorption. The observed progression of sharp zero phonon lines (ZPLs) from v(')=2 to v(')=19 in B excitation is used to derive spectroscopic constants. The ZPL broadening and the growing phonon sideband (PSB) contributions indicate an increase of matrix influence on the X-B transition with rising v('). Contributions of the PSB are parameterized with the Huang-Rhys coupling constant S, where S=1 near the potential minimum reflects the electron-phonon coupling and S=4 close to Franck-Condon maximum originates from vibrational coupling. The PSB spectral composition correlates with the matrix phonon density of states, and the ZPL broadens and shifts with temperature. Two crossings with repulsive states (between v(')=4-5 and v(')=7-9) leading to matrix induced predissociation and a third tentative one between v(')=14 and 15 are indicated by ZPL broadening, population flow, and spectral shifts. The crossing energies are close to gas phase and matrix calculations. The stepwise flow of intensity from B via repulsive states to A(') and, similarly, from the A continuum to A(') is discussed. Emission quantum efficiency of the B state decreases from near unity at v(')=0 to less than 10(-3) at v(')=19. Broadening of ZPL near crossings yields predissociation times of 5 and 2.5 ps corresponding to probabilities of 5% and 10% per round-trip for the two lowest crossings, respectively.
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Affiliation(s)
- Heide Ibrahim
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany.
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Zhang DF, Zhang B. Photodissociation Exploration for Near-Visible UV Absorption of Molecular Bromine. CHINESE J CHEM PHYS 2008. [DOI: 10.1088/1674-0068/21/01/12-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hernández-Lamoneda R, Uc Rosas VH, Bernal Uruchurtu MI, Halberstadt N, Janda KC. Two-Dimensional H2O−Cl2 and H2O−Br2 Potential Surfaces: An Ab Initio Study of Ground and Valence Excited Electronic States. J Phys Chem A 2007; 112:89-96. [DOI: 10.1021/jp077074i] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | - Nadine Halberstadt
- Laboratoire des Collisions, Agrégats, Réactivité, IRSAMC, CNRS, and Paul Sabatier University, 31062 Toulouse, France
| | - Kenneth C. Janda
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025
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Kerenskaya G, Goldschleger IU, Apkarian VA, Janda KC. Spectroscopic Signatures of Halogens in Clathrate Hydrate Cages. 1. Bromine. J Phys Chem A 2006; 110:13792-8. [PMID: 17181336 DOI: 10.1021/jp064523q] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the first UV-vis spectroscopic study of bromine molecules confined in clathrate hydrate cages. Bromine in its natural hydrate occupies 51262 and 51263 lattice cavities. Bromine also can be encapsulated into the larger 51264 cages of a type II hydrate formed mainly from tetrahydrofuran or dichloromethane and water. The visible spectra of the enclathrated halogen molecule retain the spectral envelope of the gas-phase spectra while shifting to the blue. In contrast, spectra of bromine in liquid water or amorphous ice are broadened and significantly more blue-shifted. The absorption bands shift by about 360 cm-1 for bromine in large 51264 cages of type II clathrate, by about 900 cm-1 for bromine in a combination of 51262 and 51263 cages of pure bromine hydrate, and by more than 1700 cm-1 for bromine in liquid water or amorphous ice. The dramatic shift and broadening in water and ice is due to the strong interaction of the water lone-pair orbitals with the halogen sigma* orbital. In the clathrate hydrates, the oxygen lone-pair orbitals are all involved in the hydrogen-bonded water lattice and are thus unavailable to interact with the halogen guest molecule. The blue shifts observed in the clathrate hydrate cages are related to the spatial constraints on the halogen excited states by the cage walls.
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Affiliation(s)
- Galina Kerenskaya
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA.
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Huang HY, Chuang WT, Sharma RC, Hsu CY, Lin KC, Hu CH. Molecular elimination of Br2 in 248 nm photolysis of bromoform probed by using cavity ring-down absorption spectroscopy. J Chem Phys 2006; 121:5253-60. [PMID: 15352818 DOI: 10.1063/1.1777211] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
By using cavity ring-down spectroscopy technique, we have observed the channel leading to Br(2) molecular elimination following photodissociation of bromoform at 248 nm. A tunable laser beam, which is crossed perpendicular to the photolysis laser beam in a ring-down cell, is used to probe the Br(2) fragment in the B(3)Pi(ou)(+)-X(1)Sigma(g)(+) transition using the range 515-524 nm. The ring-down time lasts 500 ns, so the rotational population of the Br(2) fragment may not be nascent nature, but its vibrational population should be. The vibrational population ratio of Br(2)(upsilon=1)/Br(2)(upsilon=0)=0.8+/-0.2 implies that the fragmented Br(2) is vibrationally hot. The quantum yield of the molecular elimination reaction is 0.23+/-0.05, consistent with the values of 0.26 and 0.16 reported in 234 and 267 nm photolysis of bromoform, respectively, using velocity ion imaging. A plausible photodissociation pathway is proposed, based upon this work and ab initio calculations. The A(1)A(2), B(1)E, and C(1)A(1) singlet states of bromoform are probably excited at 248 nm. These excited states may couple to the high vibrational levels of the ground state X(1)A(1) via internal conversion. This vibrationally excited bromoform readily surpasses a reaction barrier 389.6 kJ/mol prior to decomposition. The transition state structure tends to correlate with vibrationally hot Br(2). Dissociation after internal conversion of the excited states to vibrationally excited ground state should result in a large fraction of the available energy to be partitioned in vibrational states of the fragments. The observed vibrationally hot Br(2) fragment seems to favor the dissociation pathway from high vibrational levels of the ground state. Nevertheless, the other reaction channel leading to a direct impulsive dissociation from the excited states cannot be excluded.
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Affiliation(s)
- Hong-Yi Huang
- Department of Chemistry, National Taiwan University, Taipei, TaiwanInstitute of Atomic and Molecular Sciences, Taipei 106, Taiwan
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Goldschleger IU, Senekerimyan V, Krage MS, Seferyan H, Janda KC, Apkarian VA. Quenched by ice: Transient grating measurements of vibronic dynamics in bromine-doped ice. J Chem Phys 2006; 124:204507. [PMID: 16774353 DOI: 10.1063/1.2201749] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In both water and in ice, the absorption spectra of bromine are dramatically broadened and blueshifted, and all fluorescence is quenched. Time resolved, electronically resonant transient grating measurements are carried out to characterize the vibronic dynamics of the trapped molecule in its electronic B(3Pi0u) state in ice. Independent of the initial excitation energy, after the first half-period of motion, a vibrational packet is observed to oscillate near the bottom of the potential, near nu=1. The oscillations undergo a chirped decay to a terminal frequency of 169 cm(-1) on a time scale of taunu=1240 fs, to form the stationary nu=0 level. The electronic population in the B state decays in taue=1500 fs. Adiabatic following to the cage-compression coordinate is a plausible origin of the chirp. Analysis of the absorption spectrum is provided to recognize that solvent coordinates are directly excited in the process. The observed blueshift of the absorption is modeled by considering the Br2-OH2 complex. Two-dimensional simulations, that explicitly include the solvent coordinate, reproduce both the time data and the absorption spectrum. The observed sharp vibrational recursions can be explained by overdamped motion along the solvent coordinate, and wave packet focusing by fast dissipation during the first half-period of motion of the molecular coordinate.
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Affiliation(s)
- I U Goldschleger
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
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Hsu CY, Huang HY, Lin KC. Br2 elimination in 248-nm photolysis of CF2Br2 probed by using cavity ring-down absorption spectroscopy. J Chem Phys 2005; 123:134312. [PMID: 16223293 DOI: 10.1063/1.2047570] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
By using cavity ring-down absorption spectroscopy technique, we have observed the channel of Br2 molecular elimination following photodissociation of CF2Br2 at 248 nm. A tunable laser beam, which is crossed perpendicular to the photolyzing laser beam in a ring-down cell, is used to probe the Br2 fragment in the B 3Piou+-X1Sigmag+ transition. The vibrational population is obtained in a nascent state, despite ring-down time as long as 500-1000 ns. The population ratio of Br2(v=1)/Br2(v=0) is determined to be 0.4+/-0.2, slightly larger than the value of 0.22 evaluated by Boltzmann distribution at room temperature. The quantum yield of the Br2 elimination reaction is also measured to be 0.04+/-0.01. This work provides direct evidence to support molecular elimination occurring in the CF2Br2 photodissociation and proposes a plausible pathway with the aid of ab initio potential-energy calculations. CF2Br2 is excited probably to the 1B1 and 3B2 states at 248 nm. As the C-Br bond is elongated upon excitation, the coupling of the 1A'(1B1) state to the high vibrational levels of the ground state X 1A'(1A1) may be enhanced to facilitate the process of internal conversion. After transition, the highly vibrationally excited CF2Br2 feasibly surpasses a transition barrier prior to decomposition. According to the ab initio calculations, the transition state structure tends to correlate with the intermediate state CF2Br+Br(CF2Br...Br) and the products CF2+Br2. A sequential photodissociation pathway is thus favored. That is, a single C-Br bond breaks, and then the free-Br atom moves to form a Br-Br bond, followed by the Br2 elimination. The formed Br-Br bond distance in the transition state tends to approach equilibrium such that the Br2 fragment may be populated in cold vibrational distribution. Observation of a small vibrational population ratio of Br2(v=1)Br2(v=0) agrees with the proposed mechanism.
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Affiliation(s)
- Ching-Yi Hsu
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
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Tellinghuisen J. Erratum: “Transition strengths and potential curves for the valence transitions in Br2 from a reanalysis of the ultraviolet-visible absorption at low resolution” [J. Chem. Phys. 115, 10417 (2001)]. J Chem Phys 2003. [DOI: 10.1063/1.1527917] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
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Tellinghuisen J. Precise Equilibrium Constants from Spectrophotometric Data: BrCl in Br2/Cl2 Gas Mixtures. J Phys Chem A 2003. [DOI: 10.1021/jp027227w] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Joel Tellinghuisen
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235
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