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Updated: Jun 27, 2026

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Published on: October 9, 2020
Temperature dependence of the IR driven cis-trans isomerization of nitrous acid (HONO)
1Physikalisch-Chemisches Institut, Universitat Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Abstract:
With the help of ultrafast time-resolved infrared spectroscopy, we investigate the temperature dependence of the IR driven cis-->trans isomerization of nitrous acid (HONO) in solid Kr. We find that the lifetime of the OH-stretch vibration, as well as the final cooling into the matrix, is affected only minimally (if at all) by temperature. Nevertheless, the quantum yield of the cis-->trans isomerization reaction increases by approximately 30% to a total of 50%-70% when lowering the temperature from 30 to 15 K, whereas the trans-->cis back yield is reduced by approximately 40%. The results are discussed in analogy to Marcus theory of nonadiabatic electron transfer for the essentially barrierless case. We present a unified view of this important prototype proton transfer reaction that can explain the high cis-->trans quantum yield of close to 1.
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