Vibrational population distributions within the CO-stretching T-1u man
ifold of W(CO)(6) in room-temperature n-hexane were created by using n
ear-transform limited and linearly chirped picosecond infrared excitat
ion pulses. These pulses were characterized using the second harmonic
FROG (frequency-resolved optical gating) algorithm to determine the si
milar to 8 cm(-1)/ps chirp for both positively- and negatively-chirped
2 ps pulses. FROG and time-resolved transient difference spectra were
obtained with an InSb focal plane array detector. While unchirped and
positively-chirped excitation leads predominantly to upsilon = 1 popu
lation, negatively-chirped pulses produce excess population in the Li
= 2 level. These results are compared to predictions from density matr
ix calculations for a model potential. (C) 1998 Elsevier Science B.V.
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