Satellites of the resonance transitions of alkali atoms in mixtures with CF4

Abstract

The absorption and luminescence excitation spectra of gas phase mixtures of alkali metals atoms A (A = K, Rb, Cs) with carbon tetrafluoride molecules CF4 are studied in the region of transitions from the ground state A(2S1/2) to the lowest resonance states A(2P1/2, 3/2). It is shown that these transitions have intense satellites corresponding to the simultaneous vibrational excitation of the carbon tetrafluoride molecule, A(2S1/2) + CF4(v3=0) + hv → A(2P1/2, 3/2) + CF4(v3=1), where v3 is the IR active mode of CF4 with a vibrational quantum energy of 1281 cm–1. The satellites are relatively narrow bands (FWHM ~ 30 cm–1) slightly (< 10 cm–1) shifted to the red from the energies corresponding to the asymptotes A(2PJ) + CF4(v3=1), J=1/2, 3/2. The spectral width and position of the satellites indicate that these transitions occur at relatively large atom-molecule distances. In contrast to the majority of the studied before pair excitation processes in the gas phase, the intensity borrowing mechanism responsible for the observed satellite bands cannot be explained by the dipole-dipole interaction. Possible alternative mechanisms are discussed. It is also established that mixtures with CF4 are chemically stable including at elevated temperatures up to at least 200°C and their optical excitation results in resonance luminescence of alkali atoms. As compared to Ar, collisions with CF4 provides a higher rate of the population transfer between the A(2P1/2) and A(2P3/2) states. These results indicate that CF4 may be used as a component of the active medium of diode pumped alkali lasers.