Electronic Structure and Excited State Dynamics of Carbon-chain free radicals

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Carbon-chain free radicals such as CィイD24ィエD2H and CィイD23ィエD2N have been extensively investigated by microwave spectroscopy and radio astronomy. However, their electronic structures especially those in excited electronic states and their reaction dynamics have not been understood in detail. This project has intended to reveal details of such carbon-chain free radicals, in particular their excited electronic states and excited state dynamics.We have successfully applied stimulated emission pumping (SEP) spectroscopy to the HCCS radical to understand detailed vibronic structure in the ground electronic state, which is subjected to the Renner-Teller interaction. The present results are expected to be valuable to understand the excited state vibronic structure, which has not analyzed yet although many of vibronic bands have been observed.Visible and near infrared spectra of the CCS radical have been observed for the first time. The species has been known to be an important free radical in interstellar space. We have developed a new scheme of microwave-optical double resonance spectroscopy, which has successfully applied to the study of the CCS radical in the near infrared region.Furthermore, we have observed electronic and pure rotational spectra of a completely unknown new carbon-chain free radical, NCィイD23ィエD2O. Its linearity in the ground electronic state has been discussed based on the observed spectra. We have observed carbon-chain free radicals containing a nitrogen atom, HCィイD24ィエD2N, CHCHCN, and HィイD22ィエD2CィイD23ィエD2N by microwave spectroscopy.