Jr. Dunlop et Ea. Rohlfing, LASER-INDUCED GRATINGS IN FREE JETS .3. SATURATION-INDUCED ANHARMONICGRATINGS, The Journal of chemical physics, 100(2), 1994, pp. 856-862
We apply two-color laser-induced grating spectroscopy (LIGS) to obtain
excitation spectra of the S-1(A(1)B(1))-S-0(($) over tilde X(1)A(1))
system of jet-cooled azulene. The ground-state depletion grating creat
ed by excitation with crossed beams is probed via either the S-2(($) o
ver tilde B(1)A(1))-S-0(($) over tilde X(1)A(1)) or S-4(($) over tilde
D(1)A(1))-S-0(($) over tilde X(1)A(1)) transitions. First-order LIGS
spectra of the S-1-S-0 origin band at several grating-laser intensitie
s reveal saturation-induced line broadening and significant saturation
dips at line center. We develop a simple model, based on the anharmon
ic grating created in the saturated regime, and use it to fit the firs
t-order data. From these fits we determine a saturation parameter and
the linewidth of the S-1-S-0 origin absorption band, which is homogene
ously broadened hue to rapid internal conversion (tau similar to 1 ps)
in the S-1 state. We also observe LIGS spectra of the azulene origin
taken at the second Bragg order of the induced grating; the observed s
econd-order lineshapes are also fit with the anharmonic-grating model.