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Infrared spectrum of the helium molecular ion sup 3 He sup 4 He sup +

Thesis/Dissertation ·
OSTI ID:5597293
This dissertation is concerned with the first experimental observation of the vibration-rotation spectrum of the helium molecular ion, {sup 3}He{sup 4}He{sup +}. The Doppler-tuned fast-beam laser-resonance technique has been used. The ions produced in an electron-impact ion source from an ion beam of a few KeV and then intersect nearly colinearly with a CO IR laser beam of fixed frequency. The velocity of the ions is scanned to tune the ions into resonance with the laser frequency. Subsequent resonance detection is realized by using charge exchange processes of the ion with a target gas. Twelve spectral lines have been measured which correspond to nine different vibration-rotation transitions of the R branch in the fundamental band of the ground state of {sup 3}He{sup 4}He{sup +}. The combination of the kinematic compression of the fast-beam method and the special frequency stabilization of the CO laser render an experimental accuracy of 0.0006 cm{sup {minus}1} or 0.4 ppm. The accuracy exceeds that of the available theory by three orders of magnitude. The narrow spectral linewidth also allows partial resolution of the magnetic hyperfine structure due to helium-3. A hyperfine structure calculation has been carried out using a numerical multi-configuration self-consistent-field method. The agreement between the calculation and the observation is very satisfying.
Research Organization:
Arizona Univ., Tucson, AZ (USA)
OSTI ID:
5597293
Country of Publication:
United States
Language:
English