The lowest quartet-state of the ketenyl (HCCO) radical: Collision-induced intersystem crossing and the vibrational mode

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• 作者：Michael J. Wilhelm ; William McNavage ; Jonathan M. Smith ; Hai-Lung Dai
• 关键词：External heavy-atom effect ; HCCO ; Ketenyl ; ¦Í2¦Í2 mode of quartet HCCO ; Positive anharmonicity
• 刊名：Chemical Physics
• 出版年：2013
• 出版时间：30 August, 2013
• 年：2013
• 卷：422
• 期：Complete
• 页码：290-296
• 全文大小：1410 K

文摘

We have used time-resolved IR emission spectroscopy to examine collision induced intersystem crossing (CIISC) and deactivation of vibronically excited cis-HCCO(), generated following the 193 nm photolysis of ethyl ethynyl ether, by inert gases: He, Ar, and Xe. Observation of vibrationally excited CO(), in experiments quenched with Ar or Xe, suggest rapid CIISC due to a heavy-atom effect. Conversely, experiments quenched with He show transient signal from cis-HCCO(), and a distinct absence of CO(), suggesting that CIISC occurs only after cis-HCCO() has been quenched (i.e., CIISC is significantly less efficient with He). Inert gas CIISC rate constants for cis-HCCO() were deduced to be =(4.30.2)10^?11 , =(8.10.2)10^?11 , and =(13.00.1)10^?11 . Additionally, we report the first experimental assignment of 1785 ¡À 36 cm^?1 for the fundamental transition of the asym-CCO stretch of cis-HCCO(), which, compared with ab initio calculations, suggests that cis-HCCO() exhibits positive anharmonicity.