HOD spectroscopy and photodissociation dynamics: selectivity in hydroxyl/hydroxyl-d bond breaking

Zhang, Jinzhong; Imre, Dan G.; Frederick, John H.

doi:10.1021/j100342a030

Cited by 126 publications

(118 citation statements)

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“…3 in Ref. 16) to lie between 2 and 3 around the maximum of the absorption spectrum of gas-phase HOD. As a first approximation, we would expect roughly the same value for the branching ratio for the HOD ice photodissociation reaction computed by using MD simulations as for the branching ratio around the maximum of the absorption spectrum.…”

Section: Dynamicsmentioning

confidence: 89%

“…Isotope effects regarding the photo-chemistry of H 2 O have been studied theoretically [12][13][14][15][16] and experimentally. 3,[17][18][19][20] Absorption cross sections of gas-phase H 2 O, 14, 15, 21 D 2 O, 14,15 and HOD 13,15,16 have been calculated for the rovibrational ground state and for rovibrationally excited states, and have also been measured experimentally for gas-phase H 2 O, [18][19][20] D 2 O, 18,19 and HOD.…”

Section: Introductionmentioning

confidence: 99%

“…3,[17][18][19][20] Absorption cross sections of gas-phase H 2 O, 14, 15, 21 D 2 O, 14,15 and HOD 13,15,16 have been calculated for the rovibrational ground state and for rovibrationally excited states, and have also been measured experimentally for gas-phase H 2 O, [18][19][20] D 2 O, 18,19 and HOD. 18,22 Moreover, in other experiments the photon-induced 22 dissociation and ion-induced 23 dissociation processes of gas-phase HOD have been studied, and the branching ratios, which depend on laser frequency, 16,22,24 have been provided. Zhang et al 16 and Engel et al 13 both predicted that the There are also laboratory experiments regarding UV photodissociation of H 2 O and D 2 O ice where the ice sample is irradiated by multi-photon sources at excitation energies close to the Ly-α value.…”

Section: Introductionmentioning

confidence: 99%

“…18,22 Moreover, in other experiments the photon-induced 22 dissociation and ion-induced 23 dissociation processes of gas-phase HOD have been studied, and the branching ratios, which depend on laser frequency, 16,22,24 have been provided. Zhang et al 16 and Engel et al 13 both predicted that the There are also laboratory experiments regarding UV photodissociation of H 2 O and D 2 O ice where the ice sample is irradiated by multi-photon sources at excitation energies close to the Ly-α value.…”

Section: Introductionmentioning

confidence: 99%

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Isotope effects on the photodesorption processes of X2O (X = H,D) and HOD ice

Koning

Kroes

Arasa

2013

The Journal of Chemical Physics

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To investigate the isotope effects on the photodesorption processes of X 2 O (X = H,D) ice, molecular dynamics calculations have been performed on the ultraviolet photodissociation of an H 2 O or a D 2 O molecule in an H 2 O or a D 2 O amorphous ice surface, and on HOD photodissociation in an H 2 O amorphous ice surface, where the photodissociated molecules were located in the top four or five monolayers at ice temperatures of 10, 20, 30, 60, and 90 K. Three photodesorption processes can occur upon X 2 O photodissociation: X atom photodesorption, OX radical photodesorption, and X 2 O (or HOD) molecule photodesorption. X 2 O (or HOD) photodesorption can occur after recombination of X and OX, or after an energetic X atom photofragment kicks a surrounding X 2 O molecule from the ice surface. Isotope effects are observed for the X atom and the OX radical photodesorption as well as for the kick-out photodesorption. However, no isotope effects were noticeable for the photodesorption of recombined X 2 O molecules. The average D atom photodesorption probabilities are about a factor 0.9 smaller than those for the H atom, regardless of the isotope of the surrounding ice system. Also, the kick-out mechanism is more likely to occur if a D photofragment is created upon dissociation than if an H atom is created. These observations can be explained by more efficient energy transfer from the D atom to water molecules than from the H atom. Reasoning based on the X 2 O phonon frequencies associated with the librational modes and energy transfer efficiencies explain why the OX radical photodesorption probabilities are noticeably larger if the OX radical desorbs from a D 2 O ice system than from an H 2 O ice system. Also, the OX radical photodesorption is more probable upon dissociation of DOX (X = H,D) than upon dissociation of HOX (X = H,D), because the initial kinetic energy of the OX radical is larger if the dissociation products are D + OX than H + OX. The branching ratio of OD OH desorption following photodissociation of an HOD molecule in ice (about 1.0) is much lower than the OD OH branching ratio in gas-phase HOD photodissociation. This may lead to differences in isotope fractionation in OH(g) formation in dense and diffuse clouds in the interstellar medium.

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Section: Dynamicsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isotope effects on the photodesorption processes of X2O (X = H,D) and HOD ice

Koning

Kroes

Arasa

2013

The Journal of Chemical Physics

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“…The first excited state Ã ( 1 B 1 ) of HOD being totally repulsive, most approaches to selective control of O-H and O-D dissociation have been based on designing schemes which will transport the molecule to the desired H + O-D/H-O + D region of the repulsive Ã ( 1 B 1 ) surface using UV frequencies in the first absorption band. Considerable selectivity in dissociation of the O-H bond has been demonstrated even without prior vibrational excitation of the O-H bond, [8][9][10][11][12]20,30,[32][33][34][35] but in most cases, prior excitation of the O-H bond to ensure its deposition in the H + O-D channel on transition to the repulsive Ã ( 1 B 1 ) surface has been the more favoured route. [8][9][10][12][13][14][15][16][17][18][22][23][24]29 In case of selective dissociation of the O-D bond via transition to the repulsive first excited surface, prior excitation in the O-D stretch has been necessary.…”

Section: Introductionmentioning

confidence: 99%

Selective control of HOD photodissociation using CW lasers

2007

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Selective control of HOD photodissociation (H-O + D ← HOD → H + O-D) has been theoretically investigated using CW lasers with appropriate carrier frequency and |0, 0〉, |0, 1〉 and |0, 2〉 with zero quantum of excitation in the O-H bond and zero, one and two quanta of excitation in the O-D bond as the initial states. Results indicate that the O-H bond in HOD can be selectively dissociated with a maximum flux of 87% in the H + O-D channel from the ground vibrational state |0, 0〉. For the O-D bond dissociation, it requires two quanta of excitation (|0, 2〉) in the O-D mode to obtain 83% flux in the H-O + D channel.Use of a two colour laser set-up in conjunction with the field optimized initial state (FOIST) scheme to obtain an optimal linear combination of |0, 0〉 and |0, 1〉 vibrational states as the initial state provides an additional 7% improvement to flux in the H-O + D channel as compared to that from the pure |0, 1〉 state.

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Theoretical Concepts in Molecular Photodissociation Dynamics

Henriksen

1995

Advances in Chemical Physics

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HOD spectroscopy and photodissociation dynamics: selectivity in hydroxyl/hydroxyl-d bond breaking

Cited by 126 publications

References 4 publications

Isotope effects on the photodesorption processes of X2O (X = H,D) and HOD ice

Isotope effects on the photodesorption processes of X2O (X = H,D) and HOD ice

Selective control of HOD photodissociation using CW lasers

Theoretical Concepts in Molecular Photodissociation Dynamics

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