Authors

Citation

Ic. Lane et al., The UV absorption of ClO - Part 2. Predissociation of the A(2)Pi(Omega) state studied by ab-initio and Fermi golden rule calculations, PCCP PHYS C, 1(13), 1999, pp. 3087-3096

Citations number

44

Language

INGLESE

art.tipo

Article

Categorie Soggetti

Physical Chemistry/Chemical Physics

Journal title

PCCP PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ISSN journal

1463-9076
→ ACNP

Volume

1

Issue

13

Year of publication

1999

Pages

3087 - 3096

Database

ISI

SICI code

1463-9076(19990701)1:13<3087:TUAOC->2.0.ZU;2-J

Abstract

Ab-initio calculations at the CASSCF and MRCI level have been performed on
the valence doublet and quartet electronic states of the ClO radical in ord
er to explore the predissociation dynamics of the A(2)Pi(Omega) state (Omeg
a=1/2 or 3/2). The ab-initio calculations neglect spin-orbit coupling. Larg
e basis sets with diffuse orbitals were employed to ensure the calculated X
(2)Pi and A (2)Pi potentials match closely the available experimental data
. In total, the potential energies of fifteen valence states were computed
at a series of internuclear separations in order to map the potential energ
y curves. The X (2)Pi, A (2)Pi and a (4)Sigma(-) potentials are bound; thou
gh the latter has yet to be observed experimentally. All the other states a
re repulsive, and the lowest ten cross the A (2)Pi(3/2) component at energi
es below the upsilon' = 6 vibrational level. Using arguments based on elect
ronic configurations, candidate states for the predissociation of the A (2)
Pi(Omega) state can be selected. Simulations of the predissociation were pe
rformed by Fermi golden rule calculations for each vibrational level, using
the ab-initio repulsive potentials and RKR curves for the A (2)Pi(3/2) and
A (2)Pi(1/2) states. The vibrational dependence of the predissociation rat
e in the A (2)Pi(3/2) component was used to derive the magnitude of the ind
ividual couplings with the repulsive potentials. Comparison between the lif
etimes of the vibrational levels in the A (2)Pi(3/2) and A (2)Pi(1/2) compo
nents restricts the principal players in the predissociation to three repul
sive states: 1 (4)Sigma(Omega)(+), 2 (4)Sigma(Omega)(-) and 3 (2)Pi(Omega).
The possibility of coupling between the A(2)Pi(3/2) component and the 1 (2
)Delta state is also suspected. A marked similarity is revealed for the var
iation of predissociation rates with upsilon' for the A (2)Pi(3/2) and A (2
)Pi(1/2) components despite a spin-orbit state dependence of the absolute r
ates for individual upsilon' levels. A repulsive 2 (2)Sigma(+) state is ide
ntified which is likely to be involved in the UV photodissociation of ClO.
Similar ab-initio calculations on FO have revealed no bound excited valence
(2)Pi state correlating diabatically to the Cl(P-2) + O(D-1) dissociation
limit.