Measurement of cross sections for excitation of the 2P states of atomic hydrogen by charge-exchange collisions of protons in argon and nitrogen

Journal Article · Fri Aug 01 04:00:00 EDT 1975 · Phys. Rev., A, v. 12, no. 2, pp. 460-467

OSTI ID:4159126

Suchannek, R G; Sheridan, J R

Absolute cross sections for the excitation of the 2P states of atomic hydrogen in charge-exchange collisions of protons in argon and nitrogen were measured by observing the Lyman-$alpha$ radiation emitted in transitions from this state. Because of the lack of light standards in the vacuum ultraviolet region of the spectrum, the major problem of the measurements was the absolute calibration of the Lyman-$alpha$ photometer. This calibration was obtained from coincidence measurements of H/sub alpha/ and Lyman-$alpha$ photons in the presence of an electric field. The measurements were corrected for the effect of Doppler shift on the photometer sensitivity. For the evaluation of the coincidence measurements, the branching ratio of H/sub alpha/ transitions to the 2S state and the polarization of Lyman-$alpha$ radiation, emitted in cascade processes, were needed. These quantities were obtained from quantum-mechanical calculations for a hydrogen atom in a weak electric field. Cross sections for the 2P states were obtained in the energy range from 0.5 to 30 keV. The 2P cross sections in argon had maxima of 2.34 times 10$sup -17$ and 2.84 times 10$sup -17$ cm$sup 2$ at 3.35 and 11.86 keV, respectively, and in N$sub 2$ maxima of 2.17 times 10$sup -17$ and 2.10 times 10$sup -17$ were observed at 3.39 and 11.3 keV, respectively. The energy dependence of the measured cross sections is in agreement with that of published measurements. Differences in the absolute values are discussed.

• Research Organization: Geophysical Institute, University of Alaska, Fairbanks, Alaska 99701
• NSA Number: NSA-33-001853
• OSTI ID: 4159126
• Journal Information: Phys. Rev., A, v. 12, no. 2, pp. 460-467, Journal Name: Phys. Rev., A, v. 12, no. 2, pp. 460-467; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

640304* --Physics Research--Atomic
Molecular & Chemical Physics--Collision Phenomena
ARGON-- CHARGE EXCHANGE-- HYDROGEN IONS 1 PLUS-- ION- ATOM COLLISIONS-- NITROGEN
CROSS SECTIONS-- ENERGY DEPENDENCE-- EXCITATION-- LYMAN LINES
N60400* --Physics (Atomic & Molecular)--Collision Phenomena