Temperature dependence of resonant secondary emission in NaNO 2: Spectral behavior

Abstract

Spectral behavior of resonant secondary emission in NaNO 2 has been investigated in the temperature range from 2 to 30 K under the excitation near the v 00 line of the lowest singlet absorption. With increasing temperature, luminescence lines separated from multiple-order Raman lines become detectable even under the excitation with the off-resonance energy Δ c ≳ 13 cm -1. The intensity of the luminescence line I L( T) increases with temperature in proportion to the phonon number n( hv p, T) in the temperature range T ≲ Δ c/ k, while it increases more steeply in the range T ≳ Δ c/ k. The temperature dependence of I L( T) is ascribed to the increase in the luminescence from the v 00 level after the one-phonon assisted transition to the level induced by the off-resonant incident light. The intensity of the Raman line I R( T) decreases gradually in 2–12 K range and shows rapid drop above 12 K. The temperature dependence of I R( T) is ascribed to the dephasing of the intermediate state due to the two-phonon interaction with the reservoir.