SENSITIVITY OF LASING IN NEON-LIKE ZINC AT 21.2 NM TO THE USE OF THE PREPULSE TECHNIQUE

We report strong lasing in zinc on the neonlike 3p --> 3s, J = 0 --> 1 transition at 21.2 nm when the prepulse technique of using a low-intensity prepulse before the main optical drive pulse is used with the 1,315-mu m Asterix laser to illuminate the zinc target. Without the use of the prepulse, this line is not visible. The usual J = 2 --> 1 lines at 26.2 and 26.7 nm are observed weakly both with and without the use of the prepulse. By variation of the prepulse energy, we demonstrate that even a very weak prepulse with less than 0.1% of the main pulse energy can enable the zinc to lase at 21.2 nm.