Ab initio calculations on the X∼2B1 → X∼1A1 photoelectron spectrum of thioformaldehyde negative ion

•Additional electron causes H2CS- to change into a slightly curved umbrella structure.•The changes in the structure of H2CS- are manifested through the out of plane bending vibration and the inverse barrier appearing in the potential energy surface.•The photoelectron spectrum of H2CS− X∼2B1→ H2CS X∼1A1 at different temperatures were calculated.