Spectroscopic Characterization And Detection Of Ethyl Mercaptan In Orion

Abstract

The rotational spectrum of ethyl mercaptan, CH$_{3}$CH$_{2}$SH, has been measured in the microwave, millimeter- and submillimeter-wave regions from 8 to 880 GHz and more than 2800 distinct transition frequencies have been assigned for the $gauche$- and $trans$-conformers. Very precise values of the spectroscopic constants allowed the detection of the $gauche$-CH$_3$CH$_2$SH towards Orion KL.\footnote{L.~Kolesnikov\'{a}, B.~Tercero, J.~Cernicharo, A.~M.~Daly, J.~L.~Alonso, B.~P.~Gordon, S.~Shipman, \textit{Astrophys. J. Lett.} \textbf{2014}, accepted.} 77 unblended or slightly blended lines plus no missing transitions in the range 80~--~280~GHz support this identification. $Trans$--CH$_3$CH$_2$SH has been detected tentatively.