Abstract

Fluorescences from alkali-halide and rare-gas alkali ionic excimers have been reported by excitations of ion-beam and incoherent soft x-ray of laser-produced plasma.^1,2 As a preliminary step toward achieving an ionic excimer laser in the vacuum ultraviolet, we report for the observation of bound-free emissions from Xe⁺ Li, Kr⁺Li, Xe⁺ Rb, Kr⁺Rb, Xe⁺ Cs, and Kr⁺ Cs by relativistic electron beam pumping. The electron beam used in the experiment is same to that described in our previous work.³ The fluorescence was analyzed with a SMA composed of a 0.2-m VUV spectrometer and a model IRY-512 detector which in combination with a sodium salicylate scintillator and an optical imaging system. Figure 1 shows a typical VUV emission spectrum observed from e-beam pumped Xe/Cs mixture. A strong VUV emission band centered at 159 nm is attributed to the (XECs)⁺ ionic excimer emission. The spectrum exhibits one 4 nm wide diffuse peak at 159 nm and a weak discreat structure from 130 to 155 nm. Figure 2 shows a VUV emission spectrum observed by the electron beam excitation of a Kr/Cs mixture- The emission from the (KrCS)⁺ ionic excimer exhibits a main peak centered at 131 nm, which is slightly shorter than the position of the spectrum observed in the ion beam excitation. In addition, Xe₂^* emission in 174-nm region and weaker Kr₂^* band at 146 nm were also observed at small alkali pressures, but for alkali pressures above 4 Torr the Xe₂^* and Kr₂^* signal are quickly quenched by the alkali vapor.

© 1994 Optical Society of America