T. Efthimiopoulos et al., STUDY OF THE 5P(3 2)-4S(1/2) EMISSION IN K UNDER 2-PHOTON 4S(1/2)-6S(1/2) EXCITATION/, Journal of physics. B, Atomic molecular and optical physics, 29(22), 1996, pp. 5619-5627
It is shown that by proper use of the excitation spectra, the emission
spectra of the 5P(3/2)-4S(1/2) transition and the far-field patterns
it is possible to distinguish between competing processes involved in
the two-photon excitation to the 6S state of potassium, namely: (a) re
sonant fluorescence emission associated with the cascading spontaneous
emission (ASE) and (b) the four-wave mixing parametric process. The e
ffect of the buffer gas on the intensities of the spectra of the radia
tions emitted is discussed. Conical emission and spatial instabilities
of the excitation radiation and the 5P(3/2)-4S(1/2) emission were als
o observed for high excitation and high vapour pressure of potassium.