The UV absorption of ClO Part 2. Predissociation of the A2ΠΩstate studied by ab-initio and Fermi golden rule calculations

Lane, Ian C.; Howie, Wendy H.; Orr-Ewing, Andrew J.

doi:10.1039/a903310f

Cited by 24 publications

(29 citation statements)

References 33 publications

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“…And this state may have a strong oscillator strength and make a significant contribution to ClO photochemistry below 240 nm. 12 Toniolo et al, however, predict that this state should contribute only a fraction of 0.02 of the oscillator strength of the A 2 ⌸ state, 10 which is not consistent with the experimental result of Davis and Lee and our measurement. Figure 3 shows that the noncore sampled TOF spectra for Cl( 2 P 1/2 ) fragments taken with ϭ90°and ϭ0°are different, indicating velocity anisotropy.…”

Section: Shown Incontrasting

confidence: 99%

“…The Cl( 2 P 1/2 )ϩO( 3 P J ) channel arises from a predominately parallel transition and the wavelength invariance of this channel's yield suggests that it arises from adiabatic dynamics arising from a weak interaction of the repulsive 3 2 ⌸ i state with the A-state consistent with recent theoretical predictions. 10,12 The similarity of the results to a previous study at 248 nm suggests that the product branching ratios and contributions of excited states are not strongly dependent on wavelength throughout the continuum region from 220 to 260 nm.…”

Section: Discussionsupporting

confidence: 81%

“…However, it is unlikely that this state is reached directly since the vertical excitation energy greatly exceeds the energy of a 235 nm photon. 10,12 Excitation to the A 2 ⌸ i state followed by coupling to the 3 2 ⌸ i state beyond the Franck-Condon region is thus necessary. A one-dimensional Landau-Zener curve crossing calculation predicts that a small adiabatic splitting, assuming a crossing location near the asymptote ͑4.2 eV͒, 10 would result in a large wavelength-independent nonadiabatic curve crossing probability.…”

Section: Shown Inmentioning

confidence: 99%

“…11 Ab initio calculations suggest that the principal candidates for states which predissociate the A 2 ⌸ i state are the 1 4 ⌺ ϩ , 2 4 ⌺ Ϫ , and 3 2 ⌸ states. [10][11][12] There have only been two direct experimental studies of the UV photodissociation of the ClO radical. Davis and Lee studied the photolysis at 248 nm using molecular beam neutral time-of-flight ͑TOF͒ and concluded that channel 2 was the dominant channel.…”

Section: Introductionmentioning

confidence: 99%

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The ultraviolet photodissociation of jet-cooled ClO and BrO radicals

Zou

Kim

North

2002

The Journal of Chemical Physics

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Articles you may be interested inPhotodissociation of the BrO radical using velocity map ion imaging: Excited state dynamics and accurate D 0 0 ( Br O ) evaluation Resonance enhanced multiphoton ionization/time-of-flight measurements of the velocity and internal energy content of thermal and photochemical methyl radical sources Rev.The photodissociation dynamics of jet-cooled ClO and BrO radicals have been studied using resonance-enhanced multiphoton ionization with time-of-flight mass spectrometry. Four asymptotic electronic channels are energetically allowed for ClO photodissociation at 235 nm, although the dominant products observed at 235 nm are Cl( 2 P 3/2 ) and O( 1 D 2 ). Polarization-dependent time-of-flight profiles indicate that this channel has an anisotropy parameter of ␤ϭ1.2Ϯ0.2. Evidence for O( 3 P J ) products was detected in coincidence with Cl( 2 P 1/2 ) fragments, and we estimate that this channel constitutes Ͻ3% at this wavelength. In the photodissociation of BrO at 355 nm we observe two asymptotic electronic state channels, Br( 2 P 3/2 )ϩO( 3 P 2 ) and Br( 2 P 1/2 ) ϩO( 3 P 2 ) in a 0.75:0.25 ratio. Both channels have an anisotropy parameter of ␤ϭ1.5Ϯ0.1. Based on the measured asymptotic velocities of both channels, we have directly determined the Br-O bond dissociation energy to be 55.8Ϯ1.0 kcal/mol, providing a heat of formation for the BrO radical at 298 K of 29.7Ϯ1.0 kcal/mol in good agreement with previous spectroscopic determinations.

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Section: Shown Incontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 81%

Section: Shown Inmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The ultraviolet photodissociation of jet-cooled ClO and BrO radicals

Zou

Kim

North

2002

The Journal of Chemical Physics

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] and references therein), knowledge about other Group 16 monohalides is very poor. Among sulphur monohalides, only the lightest SF radical is mentioned in the Huber-Herzberg compendium [15], and even in this case the spectroscopic data reported are far from complete and the assignment of the only known excited state as A'II is not reliable.…”

Section: Introductionmentioning

confidence: 99%

Electronic states and transitions of the TeX (X = C1, Br, I) radicals

et al. 2002

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A b inirio multireference configuration interaction calculations including spin-orbit coupling have been carried out for the first time for valence electronic states of the TeX (X = CI, Br, I) radicals and compared with the results for the isovalent TeF and I 0 systems obtained earlier at a similar level of theoretical treatment. The calculated spectroscopic constants are in good agreement yith experimental data in the rare cases when the latter are available. It is shown that the X -r I ( s '~~n *~) ground state bonding becomes consistently weaker down the TeX group (calc. D, = 25480cm-I for TeF, 12 l00cm-I for Tel) due to the more covalent character of bonding in the heavier radicals. The first excited state, A 4C-(TC* + s*), is calculated to be bound in all systems. It is split into R 1 /2 and 3/2 comppnents, with regular ordering in the Franck-Condon region, opposite to that of the ground X -Il state. p r larger internuclear distances, the A, 4CI/2 state undergoes an avoided crossing with X2-IIl,2, which causes a shoulder in the X2 potential curve and also leads to a crossing between the A, and A2 curves and large distinctions in their vibrational frequencies. The X* + CJ* B'C-, C'A, and 1 'C+ states are calculated to lie next in energy. They are all bound in the lightest of the TeX radicals, TeF, but successiv7ly lo,se their bonding character down the group. In contrast to oxygen monohalides, the 2 -Il( o -x~x '~) state has a repulsive potential curve. Electric dipole transition moments and radiative lifetimes have also been calculated for the low lying bound states in all systems. Most of them are found to be quite weak. The A,,? + XI,' spectra are dominated by parallel contributions, with the A? + X I being the strongest one. The T values for this transition are quite similar and lie in the 17-30 ps range. Radiative lifetime values for the B + XI,? transitions demonstrate very irregular behaviour for various, TeX radicals, due to strong admixture of A4CS character to the XI,? states near the B-C-potential minimum. The A,,' C;j2,3,2 and B-C;,' states of TeX (X = C1, Br, I) still await their experimental observation. 4

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