Knowledge Bank

The ethylthio ($C2H5S$) radical was formed by 248-nm laser photolysis of diethyl disultide ($C2H5SSC2H5$) or ethyl mercaptan ($C2H5SH$) in a free jet expansion. The $B~-X~$ fluorescence excitation spectrum was recorded in the wavelength region 398 - 440 nm. Preliminary data show that the origin lies at $23519.6cm-1$ with a main progression of C-S stretching ($420.5cm-1$). Other vibrational modes at 256.0, 861.0, 1054.6 and $1203.3cm-1$ were also observed for the $B$ state. Detection of hot bands in the excitation spectrum enables assignments of three low-lying modes of the $X$ state. Detection of hot bands in the excitation spectrum enables assignments of three low-lying modes of the $X$ state: 296.2, 479.9, and $672.8cm-1$. Dispersed fluorescence spectra in the spectral region 410 - 520 nm revealed a main progression of C-S stretching ($673cm-1$ with additional vibrational modes of the $X$ state near 308, 475, 882, 1076, and $1257cm-1$. Observed vibrational wavenumbers of both $B$ and $X$ states agree with theoretical calculations by the B3LYP/cc-PVDZ+f method (for the $X$ state) and the MP2/DZP method (for both states).