On mechanisms of He I collisional excitation in He-He system

Abstract

The present work is devoted to study of He I excitation in low energy He-He collisions. The purpose of this work is the investigation of mechanisms of atomic levels excitation at collision energies, corresponding the conditions of adiabatic approximation. The results of the experimental investigation of the excitation cross sections of He I 3 1 P, 3 3 P, 3 1 D, 3 3 D levels in the collision energy range from threshold up to 500 eV (c.m. system) and degree of polarization for 2 1 S-3 1 P, 2 3 S-3 3 P, 2 1 P-3 1 D and 2 3 P-3 3 D transitions in this energy range are represented. Also the degree of polarization for 2 1 P-n 1 D transitions as function of the main quantum number (3 ≤ n ≤ 12) at the fixed collision energy is represented.PACS : 34.50.Fa

Optical emission from a ‘beam mode’ transparent cathode glow discharge

“…For ionimpact we use emission cross sections [53] with the 501.6 nm data reduced by the factor of 8 suggested by the authors to make the set consistent with higher-energy measurements [54,55], this agreeing also with others not shown [56]. For neutral-impact we considered two sets of cross sections [57,58], that show qualitative agreement over similar ranges of energies below 1 keV. Those selected [57] are of most similar size to the ion-impact data; the others are greater by around an order of magnitude after authors' corrections [59], and have excitation to 3 1 P relatively larger by a factor of around 4.…”

“…The results for singlet and triplet lines are grouped separately, and plotted against conditions of V/p (where V = V C ), for which the ordering of data points corresponds to monotonic increase in voltage and decrease in pressure. These show line intensities within each Cross sections for helium emission after excitation by (i) electrons [52], (ii) ions [53] and (iii) neutrals [57] (extrapolations to ion-impact values at 20 keV shown as dashed lines). Wavelengths are indicated as 587.6 nm, 667.8 nm, ♦ 388.9 nm and 501.6 nm.…”

“…For neutral-impact we considered two sets of cross sections [57,58], that show qualitative agreement over similar ranges of energies below 1 keV. Those selected [57] are of most similar size to the ion-impact data; the others are greater by around an order of magnitude after authors' corrections [59], and have excitation to 3 1 P relatively larger by a factor of around 4. For lines other than 3 3 P the energy range covers the rise to first maximum, showing a generally similar distribution to the lower-energy ion-impact data.…”

“…Figure 7.Cross sections for helium emission after excitation by (i) electrons[52], (ii) ions[53] and (iii) neutrals[57] (extrapolations to ion-impact values at 20 keV shown as dashed lines). Wavelengths are indicated as 587.6 nm, 667.8 nm, ♦ 388.9 nm and 501.6 nm.…”