Observation of the v = 1 ← 0 band of SH ( X2Π) with a difference frequency laser

The fundamental vibration-rotation band of SH ( X²Π) has been studied in absorption at Doppler-limited resolution with an estimated accuracy of 0.002 cm ^-1. The band origin ( ν₀ = 2598.7675 ± 0.0003 cm ^-1) and the molecular constants for the excited vibrational state ( v = 1), as well as improved molecular constants for the ground vibrational state, have been determined in a least-squares fit.