The band of ND3 studied by laser-induced amplified spontaneous emission and transient gain spectroscopy

Abstract

Abstract Two nonlinear laser spectroscopic methods have been employed for interrogating the C ′ 1 A ′ 1 → A 1 A 2 ′′ transition of ND 3 . The first method utilized laser-induced amplified spontaneous emission (LIASE) as the signal radiation. When single rovibronic levels in the C ′ 1 A ′ 1 ( 2 n , n=1–7 ) states of the ND 3 molecules were populated through two-photon excitation from the X 1 A 1 state by pulsed UV laser light, yellow LIASE was generated along the input laser axis. The q Q branches with J = K dominated both the C ′ ← X 2 0 0 excitation and C ′ → A 2 1 1 LIASE spectra. LIASE was almost perfectly polarized parallel to the polarization plane of the incident UV radiation. The second method, transient gain spectroscopy (TGS), in which the stimulated emission induced by the injection of weak DUMP radiation is detected, was also applied to the C ′ → A 2 1 1 band system. The amplification of DUMP laser intensities at the exit of the ND 3 sample cell was successfully observed when the DUMP frequencies were resonant with the specific rovibronic lines in the C ′ → A band. The maximum gain was as large as 75. TGS spectra exhibited narrower line widths than the natural line widths estimated from the lifetimes of lower levels.