Observation and Analysis of Visible Overtone Band Transitions of NH3

Abstract
A sensitive spectrometer with a ring dye laser is constructed to observe very weak visible transitions of molecules. The sensitivity is estimated to be 3×10-9/cm in the absorption coefficient. About 1000 high overtone and combination band lines with Δ v=5 of NH3 are observed in the frequency range 15260–15590 cm1. Among them, 193 lines are assigned and the rotational constants in the highly excited vibrational states are determined.