Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. I. The 1B1 states of H2O and D2O

Ashfold, Michael N. R.; Bayley, J. M.; Dixon, Ronald

doi:10.1016/0301-0104(84)80004-x

Cited by 107 publications

(32 citation statements)

References 29 publications

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“…The photodissociation of the water molecule [17][18][19] in the C state presents very interesting case of rotational state specific predissociation. As the rotational quantum number K a Ј increases, the dissociation of water molecule in the C state provides an excellent example of competition between different nonadiabatic dynamics involving at least four electronic surfaces.…”

Section: Discussionmentioning

confidence: 99%

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

Cheng

Guo

et al. 2010

The Journal of Chemical Physics

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The rotational state resolved photodissociation dynamics of D(2)O via the C state has been investigated using the D-atom Rydberg "tagging" time-of-flight technique, with a tunable vacuum ultraviolet photolysis light source. The photodissociation action spectrum of the D(2)O C<--X (3p(z)<--1b(1)) band has been recorded. The linewidths of rotational transitions have been determined by the Lorentzian profile simulation. Product kinetic energy distributions and angular distributions for individual rotational lines have been measured. From these distributions, the internal state distributions of the OD radical product as well as the state resolved angular anisotropy parameters for each rotational transition have been obtained. The dramatic variation of the OD product state distributions from different rotational excitations has been observed. These results suggest that there are two distinctive coupling channels from the C state to the lower electronic states: homogenous electronic coupling to the A((1)B(1)) state, resulting in a vibrationally hot OD(X (2)Pi) product and Coriolis-type coupling between the C((1)B(1)) state and the B((1)A(1)) state. Through the second mechanism, OD(X (2)Pi) as well as OD(A (2) summation operator(+)) products are produced. The OD(X (2)Pi) products are mainly populated in the vibrationally cold but extremely rotationally excited states. The comparison between the D(2)O and H(2)O results illustrates that the C((1)B(1))-->B((1)A(1)) pathway is relatively larger in the D(2)O photodissociation as a consequence of the isotopic effect.

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Section: Discussionmentioning

confidence: 99%

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

Cheng

Guo

et al. 2010

The Journal of Chemical Physics

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“…Unlike the rapid (fs) dissociation of

\overset{A}{true}

and

\overset{B}{true}

states, the predissociation of the

\overset{C}{true}

Rydberg state is much slower, in the order of a few picoseconds. The absorption spectrum around 124 nm shows sharp peaks and fully resolvable rotational structures can be identified . The predissociation dynamics of the

\overset{C}{true}

state depends strongly on the rotational quantum number and is an ideal model to study the rotational‐state‐specific dissociation dynamics .…”

Section: Introductionmentioning

confidence: 99%

State‐to‐state photodissociation dynamics of the water molecule

Zhou

Xie

2017

WIREs Comput Mol Sci

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Photodissociation provides an ideal proving ground for an in‐depth understanding of the microscopic mechanism and dynamics of bond breaking processes at a state‐to‐state level. After a brief outline of the requisite theory, we review the latest developments on the state‐to‐state photodissociation dynamics of the water molecule via the lowest two excited states, focusing on the absorption spectrum and product state distributions. A detailed discussion is given on the competition between different adiabatic and nonadiabatic pathways of the dissociation. Quantum mechanical studies of this prototypical system on accurate coupled potential energy surfaces not only offer an interpretation of the existing experimental results but also provide a clear and comprehensive dynamical picture of water photodissociation. WIREs Comput Mol Sci 2018, 8:e1350. doi: 10.1002/wcms.1350 This article is categorized under: Theoretical and Physical Chemistry > Reaction Dynamics and Kinetics

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“…By determining values of the recoil anisotropy parameter ␤ (ϭ ͗3cos 2 Ϫ 1͘ with defined relative to the electric vector) for several transitions we have been able to determine a much more detailed picture of the dissociation in the molecular frame than is possible when exciting to short-lived states. Earlier resonance-enhanced multiphoton spectroscopy of the C state indicated a rotational dependence to the predissociation mechanism (10)(11)(12), and rotationally excited OH(A) products were observed through their A3X fluorescence (13). There is also evidence suggesting an additional rotationally independent predissociation mechanism.…”

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confidence: 96%

Nonadiabatic dissociation dynamics in H ₂ O: Competition between rotationally and nonrotationally mediated pathways

Yuan

Cheng

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The photochemistry of H2O in the VUV region is important in interstellar chemistry. Whereas previous studies of the photodissociation used excitation via unbound states, we have used a tunable VUV photolysis source to excite individual levels of the rotationally structured C state near 124 nm. The ensuing OH product state distributions were recorded by using the H-atom Rydberg tagging technique. Experimental results indicate a dramatic variation in the OH product state distributions and its stereodynamics for different resonant states. Photodissociation of H2O(C ) in rotational states with ka ‫؍‬ 0 occurs exclusively through a newly discovered homogeneous coupling to the Ã state, leading to OH products that are vibrationally hot (up to v ‫؍‬ 13), but rotationally cold. In contrast, for H2O in rotationally excited states with ka > 0, an additional pathway opens through Coriolis-type coupling to the B state surface. This yields extremely rotationally hot and vibrationally cold ground state OH(X) and electronically excited OH(A) products, through 2 different mechanisms. In the case of excitation via the 110 4 000 transition the H atoms for these 2 product channels are ejected in completely different directions. Quantum dynamical models for the C -state photodissociation clearly support this remarkable dynamical picture, providing a uniquely detailed illustration of nonadiabatic dynamics involving at least 4 electronic surfaces.photochemistry ͉ water ͉ photodissociation ͉ stereodynamics ͉ VUV photolysis W ater vapor absorbs light at all wavelengths in the vacuum UV region below 200 nm, resulting in fragmentation leading to the production of H and OH free radicals. The OH radical product of this unimolecular process is particularly important through its role in interstellar chemistry (1, 2). Extensive experimental and theoretical studies have revealed a rich structure of absorption bands in this spectral region, and have uncovered several active dissociative mechanisms. However, in most of these studies the excitation of the H 2 O parent molecule has been through dissociative continua, so that the observed dynamics relate to averages over an ensemble of molecules in a range of quantum states.In contrast, the present study uses a tuneable VUV laser to excite H 2 O through an electronic state that is sufficiently longlived to exhibit resolved rotational structure. This reveals 2 completely different dissociation pathways that produce strikingly different rovibrationally excited OH products. Furthermore, the competition between these 2 channels shows a strong dependence on the excited rotational quantum numbers and on the direction of mutual recoil of the H and OH fragments.These studies have led to an understanding of how the dissociation dynamics are controlled by the topologies of the nuclear potential energy surfaces of this model system. Absorption by H 2 O between Ϸ140 and 200 nm is to the first excited singlet state, labeled Ã and of symmetry 1 B 1 . The photodissociation on this state has been studied at both 19...

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Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. I. The 1B1 states of H2O and D2O

Cited by 107 publications

References 29 publications

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

State‐to‐state photodissociation dynamics of the water molecule

Nonadiabatic dissociation dynamics in H ₂ O: Competition between rotationally and nonrotationally mediated pathways

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Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. I. The 1B1 states of H2O and D2O

Cited by 107 publications

References 29 publications

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

Rotational state specific dissociation dynamics of D2O via the C̃ electronic state

State‐to‐state photodissociation dynamics of the water molecule

Nonadiabatic dissociation dynamics in H 2 O: Competition between rotationally and nonrotationally mediated pathways

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Nonadiabatic dissociation dynamics in H ₂ O: Competition between rotationally and nonrotationally mediated pathways