We studied ultrafast photodissociation reaction of diphenylcyclopropenone (DPCP) in solution by time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS) using sub-6-fs pulses. The obtained femtosecond time-resolved Raman data of excited-state DPCP did not show any noticeable spectral change during its lifetime of 180 fs. This indicates that photoexcited DPCP is trapped at the excited-state potential energy minimum before undergoing the photodissociation, which is consistent with the predissociation picture of ultrafast photodissociation reaction of DPCP. The present study demonstrates the high capability of TR-ISRS for structural characterization of short-lived reactive transients that decay within only a few hundreds of femtoseconds.

我们通过时间分辨的脉冲激发拉曼光谱法（TR-ISRS）使用sub-6-fs脉冲研究了溶液中二苯基环丙烯酮（DPCP）的超快光解离反应。激发态DPCP的飞秒时间分辨拉曼数据在其180 fs的寿命期间未显示任何明显的光谱变化。这表明光激发的DPCP在进行光解离之前被俘获在激发态势能最小值，这与DPCP的超快光解离反应的预解离图一致。本研究证明了TR-ISRS能够对仅在几百飞秒内衰减的短时反应性瞬态进行结构表征。