THE PHOTOABSORPTION SPECTRUM OF NA-CENTER-DOT-CENTER-DOT-CENTER-DOT-FH VAN-DER-WAALS MOLECULE - COMPARISON OF THEORY AND EXPERIMENT FOR A HARPOONING REACTION STUDIED BY TRANSITION-STATE SPECTROSCOPY
Ms. Topaler et al., THE PHOTOABSORPTION SPECTRUM OF NA-CENTER-DOT-CENTER-DOT-CENTER-DOT-FH VAN-DER-WAALS MOLECULE - COMPARISON OF THEORY AND EXPERIMENT FOR A HARPOONING REACTION STUDIED BY TRANSITION-STATE SPECTROSCOPY, The Journal of chemical physics, 108(13), 1998, pp. 5378-5390
The photodissociation of Na ... FH van der Waals molecules in the 1.5-
2.3 eV energy region is a very interesting system for transition state
spectroscopy, because the potential energy surfaces for electronicall
y excited states funnel the system down to the ground electronic state
in a critical region where detailed features of the potential energy
surfaces may be important in determining the branching probability bet
ween the harpooning reaction to form NaF or the dissociative E-->V ene
rgy transfer process to form vibrationally excited HF. We used an anal
ytic representation. reported earlier, of the potential surfaces for t
he two lowest A' electronic states of NaFa I as well as separable fits
for two higher excited potential surfaces to simulate the experimenta
l photodepletion spectrum of the Na FI-I van der Waals molecule. Franc
k-Condon analysis was performed for the (X) over tilde (2)A' --> (2)A'
, (X) over tilde (2)A' --> (B) over tilde (2)A '', and (X) over tilde
(2)A' --> (B) over tilde' (2)A' transitions to predissociative states
of the exciplex by making a separable approximation in Jacobi coordina
tes. Theoretical simulation based on ab initio energies and transition
dipole moments produced an excitation spectrum that is in good agreem
ent with the experimental data. Including the dependence of the transi
tion dipole moment on nuclear geometry had only a small quantitative e
ffect on the calculated photoabsorption spectrum. The present calculat
ion, in spite of the approximations involved, provides a semiquantitat
ive description of the experimental spectrum of the resonance states i
n the funnel and allows us to explain all the main features of the spe
ctrum. (C) 1998 American Institute of Physics. [S0021-9606(98)00913-1]
.