AN INTERFEROMETRIC TECHNIQUE OF DENSITY MEASUREMENT APPLIED TO ALKALI METAL VAPORS ORIENTED BY OPTICAL PUMPING. (thesis)

Technical Report · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4681749

Jarrett, S M

The results of the application of an interferometric technique of density measurement to alkali metal vapors oriented by optical pumping are presented. Two experimente were performed. First, a study of the dependence of tue signal strengths in the optical pumping of a Na vapor on the Na vapor density, spectral composition of the pumping light and buffer gas pressure was made and compared witu a calculation of tuese signals. In the second, a determination of the Rb/sup 85/--Rb/sup 87/ spin exchange cross section was accomplished utilizing the techniques developed in the first experiment. Previous spin exchange cross section measurements using optical pumping methods had very large uncertainties due to poor determinations of alkali metal vapor densities. A scanning Fabry-Perot interferometer was constructed to measure tue densities in optical pumping cells. Spectral profiles of the light transmitted through the cell at room temperature and at temperatures at which optical pumping experiments were performed could be obtained by use of this instrument. These profiles were compared to yield the absorption coefficient as a function of frequency. A knowledge of the integrated absorption coefficient and the lifetime time of an alkali atom in the excited state allowed the density to be calculated. The error in thamethod was determined by the uncertainty in tae lifetime, finite resolution effects, and errors in determining the integrated absorption from the spectroscopic data. The method was estimated to be reliable to about 11%. The results of the Na experimert are presented in the form of graphs of optical pumping signal strengths as a function of density for different spectral compositions of the pumping light and buffer gas pressures. The graphs could be used to estimate vapor densities in other optical pumping experiments with an accuracy of about 50%. The results of the Rb experiment yielded a spin exchange cross section for Rb/sup 85/--Rb/sup 87/ collisions of (1.70 plus or minus 0.21) x 10/sup -14/ cm/sup 2/ . This determination was more than an order of magnitude more accurate than previous cross section determinations using optical pumping primarily because of the improved density measurement. The work is in good agreement with the electron paramagnetic resonance experiments of Sands and Moos. (auth)

• Research Organization: Michigan. Univ., Ann Arbor
• NSA Number: NSA-17-032047
• OSTI ID: 4681749
• Report Number(s): TID-19198
• Country of Publication: United States
• Language: English

Related Subjects

ABSORPTION
ALKALI METALS
CHEMISTRY
CROSS SECTIONS
DENSITY
ELECTRONS
FREQUENCY
IMPURITIES
INTERACTIONS
INTERFERENCE
LIFETIME
LIGHT
MAGNETIC RESONANCE
NUMERICALS
OPTICAL PUMPING
POLARIZATION
RUBIDIUM 85
RUBIDIUM 87
SODIUM
SPECTRA
SPIN
TEMPERATURE
VAPORS