Photodissociation of acetone revisited: Femtosecond transient absorption of S1 state and highly excited Rydberg state in the gas phase

• Published in: Bulletin of the Korean Chemical Society Vol. 43; no. 5; pp. 724 - 730
• Main Authors: Jin, Seung Min, Yang, Ilseung, Kim, Hyung Min
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley‐VCH Verlag GmbH & Co. KGaA 01.05.2022; 대한화학회
• Subjects: acetone; gas phase; photodissociation; Rydberg state; transient absorption; 화학
• ISSN: 1229-5949; 0253-2964; 1229-5949
• DOI: 10.1002/bkcs.12514

Photodissociation dynamics of acetone in gas phase were, for the first time, investigated using the pump‐probe technique of femtosecond transient absorption. To obtain a genuine time profile of nR state, we employed 200‐nm and 400‐nm pulses for two‐photon excitation and three‐photon excitation, respectively. In gas phase of acetone, the extraordinarily stable nR state originated from nR states in the Franck–Condon region, whose decay time constant was 350 ± 10 fs, was observed after excitation by three‐photon absorption of 400‐nm pulses. In the low‐power case of 267 nm, the photodissociation dynamics in the S1 state by one‐photon absorption showed that acetone was completely dissociated into two methyl radicals and C=O via an acetyl radical intermediate with a lifetime of 200 ± 10 fs. In the high‐power case of 267‐nm light, we interpreted the transient, although this is a subject of ongoing debate, as caused by both the photodissociation dynamics of the S1 state for a fast component and the dynamics of nR states for long‐lived species. The photodissociation of acetone in the Rydberg state (nR) was investigated with transient absorption method. One‐photon excitation and two‐photon excitation demonstrate different photodissociation mechanism in potential energy surface.