Soft x-ray gain in the alkali earths

An unsuccessful attempt was made to observe gain in low pressure sodium vapor at 372 A at an x-ray pumping power level of 0.1 GW/cm(2) . As a result we suggest that high density alkali-earth vapors be used instead. With a system of tunable dye lasers of moderate power, it should be possible to reduce substantially the lower laser level population and achieve gains on the order of 1-3 cm(-1). The calculations reported verify this. The additional outer electron in the alkali-earths is necessary to use the dye laser scheme. The tradeoff is that the upper laser level can Auger decay. Our calculations indicate that this is not too severe a limitation in Ca. Since the calculations may be in error, we further suggest that the dye laser scheme is applicable to alkali-earths which have been preexcited to levels for which Auger decay is forbidden in LS coupling.