Laser-induced amplified spontaneous emission from the 3d and nf Rydberg states of NO

Amplified spontaneous emission (ASE) from single rotational levels of 3d si gma, pi H (2)Sigma(+), H' (2)Pi and nf (n = 4-6) Rydberg states of NO has b een investigated through optical-optical double resonance excitation via th e A (2)Sigma(+) state. The H, H' --> 3p sigma, pi D (2)Sigma(+), C (2)Pi (0 ,0) systems were rotationally resolved. The mixing of the C (2)Pi (upsilon = 0) state with the valence B (2)Pi (upsilon = 7) state explained the rotat ional pattern successfully. The degree of polarization of ASE for these tra nsitions was measured and compared with the theoretical values of the corre sponding resonant fluorescence. As the major ASE relaxation channels from t he 4f and 5f (upsilon = 0) states, transitions down to the 3d and 4d (upsil on = 0) Rydberg series were identified, respectively. A new ASE relaxation pathway, 6f --> 5g, was found in addition to the 6f --> 5d band. The ASE fr om the 7f (upsilon = 1) state located above the ionization threshold was ob served for the first time. The spectral profiles were discussed briefly in connection with the lifetimes of the upper levels. (C) 2000 Elsevier Scienc e B.V. All rights reserved.