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Title:NONRADIATIVE DECAY ROUTE OF CINNAMATE DERIVATIVES STUDIED BY FREQUENCY AND TIME DOMAIN LASER SPECTROSCOPY IN THE GAS PHASE, MATRIX ISOLATION FTIR SPECTROSCOPY AND QUANTUM CHEMICAL CALCULATIONS
Author(s):Ebata, Takayuki
Subject(s):Mini-symposium: Multiple Potential Energy Surfaces
Abstract:The nonraddiative dececy route involving trans $rightarrow$ cis photo-isomerization from the S$_1$ ($pi$$pi$*) state has been investigated for several trans-cinnamate derivatives, which are known as sunscreen reagents. We examined two types of substitution effects._x000d_ _x000d_ One is structural isomer such as ortho-, meta-, and para-hydroxy-methylcinnmate (o-, m-, p-HMC). The S$_1$ lifetime of p-HMC is less than 8 ps at zero-point level, and it undergoes rapid S$_1$ $rightarrow$ $^1$n$pi$* $rightarrow$ T$_1$ decay via multiple conical intersections. Finally, the trans $rightarrow$ cis isomerization proceeds in the T$_1$ state. On the other hand, both o- and m-HMC show very slow decay. Their S$_1$ lifetimes are in the order of 100 ps even at the excess energy of 2000-3000 wn. _x000d_ _x000d_ The other is the effect of the complexity of ester group in para-subsitituted species, such as para-methoxy-methyl, -ethyl and -2ethylhexyl cinnamate (p-MMC, p-MEC, p-M2EHC). p-MMC and p-MEC show sharp S$_0$ $rightarrow$ S$_1$ ($pi$$pi$*) vibronic bands, while p-M2EHC shows only broad structureless feature even under the jet-cooled condition. In addition, we found that the S$_0$ $rightarrow$ $^1$n$pi$* absorption appears at 1000 wn below the S$_0$ $rightarrow$ S$_1$ ($pi$$pi$*) transition in p-MEC and p-M2EHC, but not in p-MMC. Thus, the complexity of the ester group is very important for the appearance of the $^1$n$pi$* state.
Issue Date:6/20/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/97182
DOI:10.15278/isms.2017.TG02
Date Available in IDEALS:2017-07-27


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