SHORT WAVELENGTH LASER CALCULATIONS IN THE Be I, B I AND C I ISOELECTRONIC SEQUENCES

Short Wavelength Laser Calculations in the Beryllium, Boron 2 and Carbon Isoelectronic Sequences Level populations of the 2s3p, 2s 3p 2 and 2s 2p3p configurations in ions of the Be I, R I and C I isoelectronic 2 sequences can be inverted with respect to populations of the 2s3s, 2s 3s 2 and 2s 2p3s configurations by electron collisional pumping. In the case of B I and C I ions, the process is analogous to the process for Ne-like ions which has lately received considerable attention. In the case of Be I ions, the inversion is a consequence of the slow radiative decay of the 3 3 2s3p P2 and 2s3p Po levels. Level populations are calculated for Be-like, R-like and C-like ions with atomic number Z between 18 and 36 and for electron densities from 1015 to For each of the Be I and B I isoelectronic sequences, 20 levels are involved with principal quantum number n equal either to 2 or 3. For the C I isoelectronic sequence 46 levels are involved. Using the level populations, gain coefficients are 2 2 calculated for transitions of the type 2s3s 2s3p, 2s 3s 2s 3p and 2 2 2s 2p3s 2s 2p3p. The calculated gain coefficients are compared to previous calculations. At high electron densities where collisional mixing of the excited levels becomes important, the intensities of the X-ray k m transitions from the 2s 2p 3p levels decrease relative to the X-ray transitions from the 2skzpm3s and 2 ~ ~ 2 ~ " 3 d levels where k=l, m=O or k=2, m=0,1. The density dependence of these X-ray line ratios is calculated elsewhere 116,171. These line ratios represent a promisinp: diagnostic for 2 2 electron density. Finally, the opacities of the 2s2p 2~38, 2s 2p 2s 3s 2 and 2s22p2 2s 2p3s transitions are discussed for plasma parameters for which a reasonable gain can be achieved.