Hole-burning spectra of m-fluorophenol/ammonia (1:3) clusters and their excited state hydrogen transfer dynamics

Abstract

Hole-burning spectra of m-fluorophenol/ammonia (1:3) clusters are measured by four-color UV-near IR-UV-UV hole-burning spectroscopy. Cis and trans isomers of the cluster are clearly distinguished in the (1:3) cluster. Picosecond time evolutions of the excited state hydrogen transfer (ESHT) reaction in the (1:3) clusters are measured by the ion depletion due to 3p-3s Rydberg transition of reaction products ·NH4(NH3)2 lying in the near infrared region. From the wavelength dependence of the time evolution, we have concluded 1) the initial formation of a metastable ·NH 4-NH3-NH3 radical and 2) successive isomerization to the most stable NH3-·NH4-NH 3 radical in both cis and trans isomers. The reaction lifetimes of ESHT are determined by the rate equation analysis as 32.4 and 31.8 ps for the cis and trans isomer, respectively, and the isomerization and its back-reaction lifetime of both isomers are determined to be 3.3 ps and 11.2 ps. The almost same reaction rates are consistent with the similarity of the hydrogen bond networks in both clusters. 2+2 colors needed: The coexistence of cis and trans isomers in m-fluorophenol/ammonia (1:3) clusters is evidenced by four-color hole-burning spectroscopy (see picture). Picosecond time evolutions of the excited state hydrogen transfer (ESHT) reaction are measured by monitoring ion depletion. The time constant of ESHT is almost the same in both isomers, 32.4 ps and 31.8 ps for cis- and trans-m-FPhOH-(NH3)3, respectively. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.