Laser Spectroscopy and Lifetime Measurements of the S1 State of Tetracyanoquinodimethane (TCNQ) in a Cold Gas-Phase Free-Jet |
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Authors: | Nobumasa Chaki Dr Satoru Muramatsu Yuji Iida Seiya Kenjo Prof?Dr Yoshiya Inokuchi Prof?Dr Toshifumi Iimori Prof?Dr Takayuki Ebata |
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Institution: | 1. Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan;2. Department of Applied Chemistry, Muroran Institute of Technology, Muroran, 050-8585 Japan |
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Abstract: | The S1 electronic state of 7,7,8,8-Tetracyanoquinodimethane (TCNQ) has been investigated by laser induced fluorescence (LIF), dispersed fluorescence (DF) spectroscopy, and lifetime measurements under jet-cooled conditions in the gas-phase. The LIF spectrum showed a weak origin band at 412.13 nm (24262 cm?1) with prominent progression and combination bands involving vibrations of 327, 1098, and 2430 cm?1. In addition, very strong bands appeared at ~363.6 nm (3300 cm?1 above the origin). Both the LIF and DF spectra indicate considerable geometric change in the S1 state. The fluorescence lifetime of S1 at zero-point level was obtained to be 220 ns. This lifetime is 40 times longer than the radiative lifetime estimated from the S1?S0 oscillator strength. Furthermore, the lifetimes of the vibronic bands exhibited drastic energy dependence, indicating a strong mixing with the triplet (T1) or intramolecular charge-transfer (CT) state. This study is thought to disclose intrinsic nature of TCNQ, which has been well known as a component of organic semiconductors and a versatile p-type dopant. |
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Keywords: | Electronic spectrum TCNQ laser spectroscopy supersonic jet S1 lifetime |
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