5314027768

POSTER SESSION. H22

RADIATIVE DECAY PROCESSES IN THE 6s AND 7s RYDBERG STATES OF NO

KOICHI TSUKIYAMA. Department of Chemistry, Science Univer-sity of Tokyo, Shinjuku, Tokyo 162-8601, Japan.

A novel spectroscopic techniąue involving amplified spontaneous emission (ASE) is pre-sented to populate single rotational levels of the predissociative 6s<7T²E^f and 7s<tZ²E⁺ Rydberg States of the NO molecule. In this excitation scheme, the 3pcrD²E⁺ State serves as the intennediate State: The first pumping from the ground State to A²£⁺ is performed with UV radiation around 226 nm and the population in the A²E'^ł State is then excited to the 4s<tE²E⁺ State with visible radiation around 600 nm. A part of the population in the E²E⁺ State is automatically transfered to the D²E⁺ State by the ASE deexcitation process. which is followed by cxcitat ion to the higher Rydberg States by the third pumping light. This regiine needs radiation from three tunable lasers and includes four resonant transitions, and may be called three color quadruple resonance accordingly.

Significant findings are as follows:

1.    When the single rotational levels in the T²E* State were pumped, the ASE transition down to the 5ptfR^JE⁺ State around 8.9 /nn was identified as a major radiative deexcitation

process.

2.    When the Z²E⁺ statc was populated, the ASE from OpcrY²^ to T²E⁺ around 11.5 fim was observed. The existence of this cascading ASE transition indicatcs that the initial ASE decay channel is from Z²E⁺ to Y²E⁺, though this system is located beyond our dctection limit.

These obsenrations show that the ASE relaxation channel should be taken into consid-erati(»n as a third radiative process in addition to fluorescence and phosphorescence and that a sensitiv(‘ probe of ’dark States’ is possible by detecting ASE as an experimental observable.