Cross-Sections for electron-impact excitation of Ca I and Ca II

Abstract

143 line emission cross-sections of Ca I and 15 line emission cross-sections of Ca II have been measured at an electron energy of 30eV. The optical excitation functions (OEF) are recorded in a range of electron energy from 0 to 200eV: 59 OEF for Ca I and 5 OEF for Ca II. The investigated lines are located in a spectrum region 227-745 nm. For the cross-sections of 5 singlet series and 10 triplet ones of Ca I, consideration has been given to series relationships that are characterized by the power relationship between the cross-section value and the principal quantum number of the upper level. Deviations from the power relationship take place in the perturbed Ca I series. The perturbations manifest themselves also by changing the OEF shape.

Electron impact excitation cross sections of 1 F o levels of the strontium atom

“…However, study of the excitation of the Rydberg states by electron impact became possible only after appearance of the extended crossed-beam method [3]. The first convincing results were obtained for Rydberg levels of the helium atom [4], then some metals were studied such as aluminum [5], calcium [6], etc. In recent years, analogous results have been obtained for some triplet levels of strontium [7,8].…”

“…The extended crossed-beam method [4,6,9] was used to conduct the experiment. To form the atomic beam, strontium was vaporized from a tantalum crucible heated by an electron beam to a temperature of 1000 K. At that temperature, the concentration of atoms in the zone of intersection of the electron and atomic beams reached 2.5⋅10 10 cm -3 .…”

“…Detailed discussion of the technique and procedures for experiments with extended crossed beams is included in [6][7][8].…”

“…With further increase in n, the energy interval continues to decrease, but extremely slowly, and for n = 20 the energy interval is ∆E = 0.84 cm -1 ; and for n = 26, ∆E = 0.44 cm -1 . Unfortunately, to date the behavior of the excitation cross sections in the perturbed series has not been the subject of theoretical treatment, and extensive available data (see, for example, [5,6]) cannot be compared with the results of calculations. As noted earlier in [5,6], besides the irregularity of the absolute values of the cross sections in the spectral series, a perturbation may also appear in the behavior of the optical excitation functions.…”

“…Unfortunately, to date the behavior of the excitation cross sections in the perturbed series has not been the subject of theoretical treatment, and extensive available data (see, for example, [5,6]) cannot be compared with the results of calculations. As noted earlier in [5,6], besides the irregularity of the absolute values of the cross sections in the spectral series, a perturbation may also appear in the behavior of the optical excitation functions. This is quite pronounced for the optical excitation functions of the 2 D series of the aluminum atom [5].…”