Abstract

Recent studies^1,2indicate that the Na₂violet diffuse bands are an attractive candidate for a short-wavelength chemically pumped laser. These excimer transitions have now been analyzed and unambiguously assigned using single-mode laser excitation; they arise from the superimposition of two distinct continuum (bound-free) emission bands—one singlet $\left(2^1{\Sigma }_u^{+}-X^1{\Sigma }_g^{+}\right)$ and one triplet (primarily $2^3{\Pi }_g-1^3{\Sigma }_u^{+}$).¹In beam experiments, the reaction Na₃+ X → (NA₂)* + NaX(where X= Cl, Br, I) yields direct and efficient chemiluminescence, including emission in the singlet violet band, with sharp bimodal excited state vibrational distributions; the fluorescence resembles that characterizing optically pumped alkali dimer lasers.²In sodium heat pipe ovens, the violet bands have been efficiently produced using various pumping techniques. The selectivity probably arises from the near-resonant dissociative recombination process ${\text{Na}}_3^{+}+{\text{e}}^{-}\to {\text{Na}}_2^{*}\left(2^1{\Sigma }_u^{+}\text{or}{2}^3{\Pi }_g\right)+\text{Na}$. Substantial gain and minimal absorption have been measured in the violet in high density Na vapor pumped by a cw krypton laser. Similar possibilities exist for other alkali metals.

© 1986 Optical Society of America