On SH Molecules in Umbral Spectra

Following our predictions on detectability, very weak lines of the SH molecules have been reported as identified in the photospheric spectrum of the Sun. This could be the first detection of a mercapto radical in the solar spectrum, thus placing confidence in the solar abundance of Sulfur. The observations additionally tested the utilized theoretical band oscillator strength. Sunspots being cooler than the photosphere are the hosts to a large number of molecular species. However, owing to photospheric radiation scattered into the observed umbra, the discoverers could not detect the lines of SH in the sunspot spectrum where they are expected to show larger than the photospheric equivalent widths (EWs in short). Detection of weak lines in photospheric spectrum coupled with a no-detection of the relatively strong same lines in the sunspot spectrum might cause doubts on the detection itself. The above problem is investigated here in detail with a choice on photospheric and sunspot models and micro-turbulence values. The new results indicate that the predicted sunspot lines are about half intense than reported before and the lines remain of detectable strengths. Further, a need for a laboratory determination of oscillator strengths is felt.

K. Sinha · 2014