Shattering the myth of the resonantly photo-pumped neon-like titanium laser

摘要

Several years ago neon-like titanium (Z = 22) was made to lase at 326 (angstrom) on the 3p (yields) 3s (J = 0 (yields) 1) transition. At the time it was suggested that the lasing may be due to resonantly photo-pumping the neon-like titanium 2p (yields) 4d lines using 3s (yields) 2p and 3d (yields) 2p lines in carbon-like and nitrogen-like titanium which results in lasing on the 3p (yields) 3s transition in neon-like titanium. The strongest argument for this explanation was that adjacent elements (scandium and vanadium) did not lase while titanium was unique in having the above mentioned resonance. In addition a prepulse was required to make the titanium lase, suggestive of the formation of a low density plasma, and the plasma was very overstripped, so the above mentioned pump lines should be quite strong for photo-pumping. We have reinvestigated this laser system and will present results which show lasing on the 3p (yields) 3s (J = 0 (yields) 1) transition in neon-like chromium (Z = 24), iron (Z = 26), and nickel (Z = 28) at 285, 255, and 231 (angstrom) respectively. This destroys the myth of titanium being unique and makes highly unlikely that the previously mentioned photo-pumping mechanism is playing a significant role in the titanium laser. The 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 when illuminating a thick slab target. This allows the proper conditions for gain and laser propagation for low Z neon-like ions and may also be applicable to other systems such as low Z nickel-like ions. We also will present experiments done on other low-Z materials and offer an explanation as to how the hyperfine effect is destroying the gain of neon-like ions with odd Z.