Left panel: experimental spectra of the 54_7,* – 53_7,* transitions of trans-HCSSH, with total integration time of 146 s and 3 ms of time constant. Right panel: experimental spectra of the 53_7,* – 52_7,* transitions of cis-HCSSH with total integration time of 87 s and 3 ms of time constant. Both panels: The K_a = 7 asymmetry doublet is not resolved. The red traces indicate the resulting line profile fitted with the proFFit code (see text).