The absorption of light by calcium vapour (2100 to 1080 Å)

Abstract

Continuous absorption and line absorption of radiation in calcium vapour has been measured from the 4 s 4 s 1 S 0 → 4 snp 1 P 1 series limit at 2028 to 1080 Å. Two perturbed series of auto-ionization lines (4 s 4 s 1 S 0 → 3 dnp 1 P 1 and → 3 dnp 3 P 1 ) are recorded and analyzed. A second series limit is observed at 1589 Å. This is probably two unresolved limits corresponding to the two series of auto-ionization lines. No absorption lines are observed on the short wavelength side of 1589 Å. The f -values of the lines vary from 2.4 x 10 -2 to 6 x 10 -5 and the half-lives (calculated from measurements of the half-widths of the lines) vary from 30 to 260 x 10- 15 s. The f -value for the 4 s 4 s 1 S 0 → 4 snp 1 P 1 continuum is estimated to be 0.012 (including an allowance for a portion below 1589 Å) and the f -value for the continua from wavelength 1589 to 1080 Å corresponding to the two series of auto-ionization lines is estimated to be 0.003. The measured value of the absorption near 2028 Å is about one-fiftieth of the theoretical value which has been used in astrophysical calculations.

Photoabsorption of alkali and alkaline earth elements calculated by the Scaled Thomas Fermi method

“…The term system of MgI is disturbed, so the 3snd 1D series is disturbed by the 3p 2 1D term, and the function c~,, l(~) increases with n in a nonlinear form for this series, so an extrapolation is difficult and un- with Numerovs procedure including the correction of Olver [45]. Figure 14 shows the cross section for the ground state of Ca I calculated with STF, STFP and QDM and the experimental results of Hudson and Ditchburn [46]. The large differences between the various results are striking 9 For energies between 0.02 and 0.15 Ryd strong autoionization lines are dominating the experimental cross section.…”