K. Tanimura, 3-PHOTON-EXCITATION SPECTROSCOPY FOR THE EXCITON RELAXATION IN ALKALI-HALIDES, Journal of the Physical Society of Japan, 65(11), 1996, pp. 3672-3675
The yields of sigma and pi luminescence due to self-trapped excitons h
ave been measured upon the three-photon excitation (TPE) which gives r
ise to the resonance on the upper branch of the lowest exciton-polarit
on in NaCl and KI. Both the sigma and pi luminescence are induced by t
he TPE in the whole wavelength range of the resonance, and the yield o
f the sigma luminescence relative to that of the pi luminescence is as
high as that by the conventional band-to-band excitation, showing str
ong contrast to the result of the one-photon excitation (OPE) spectros
copy. The different feature of the sigma-luminescence excitation in TP
E from that in OPE has been discussed.