Some features of the evaporation of magnesium and lead by quasi-cw laser radiation

An investigation was made of the action of quasi-cw neodymium laser radiation of approximately 0.6 msec duration and having a power density q <10 MW/cm² on magnesium and lead targets at reduced densities of the surrounding air. Measurements were made of the average recoil pressures on the target and the distribution of the refractive index n over the volume of the vapor jet was determined for various q. It was found that the increase in n with increasing q ceased at q ≈ 2 MW/cm² for magnesium and at q ≈ 1 MW/cm² for lead, whereas the pressures remained proportional to q. This result can be attributed to an increase in the electron density in the vapor jet.