Reinterpretation of the neon-like titanium laser experiments

Abstract

We present results that show lasing on the 3 p ->3 s ( J = 0->1) transition in neon-like chromium ( Z = 24), iron ( Z = 26), and nickel ( Z = 28) at 28.5, 25.5, and 23.1 nm, respectively. These results destroy the uniqueness of the lasing observed several years ago in neon-like titanium ( Z = 22) at 32.6 nm on the same transition and makes highly unlikely the hypothesis that resonant photopumping is playing a significant role in the titanium laser. The titanium, chromium, iron, and nickel experiments all require a prepulse in order to lase, and our calculations suggest that the prepulse is an exciting new way to create a uniform low-density plasma that allows the proper conditions for gain and laser propagation for low-Zneon-like ions when illuminating a thick slab target. We also present an observation of hyperfine splitting in neon-like niobium at 14.6 nm and offer an explanation as to how the hyperfine effect is reducing the gain of neon-like ions with odd Z .