NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The broadening of the calcium resonance line in a high-temperature helium atmosphereThe paper describes experimental measurements of the shape of the Ca I resonance line at 4227 A in a high-temperature helium atmosphere. A ballistic piston compressor was used to produce hot helium in the temperature range from 3000 to 7000 K and the number-density range from 2 to 4 by 10 to the 20th power per cu cm, which conditions approximate those postulated for the atmospheres of certain cool white-dwarf stars. The Boltzmann temperature of the calcium atoms was measured by the brightness-emissivity method, the absorption line shape was measured with a twelve-channel polychromator, and the helium kinetic temperature was calculated from the equation of an ideal gas. The observed deviation from thermodynamic equilibrium is illustrated. The value of the ratio of the damping constant to the helium number density at 5000 K is found to be 45 (+ or - 4) by 10 to the -22nd power A cu cm, or 4.7 (+ or - 0.4) by 10 to the -9th power rad/s cu cm. It is noted that no existing line-broadening calculation for the calcium-helium system is consistent with the present results. Recent studies of the 4227-A line in spectra of the sun and the white dwarf van Maanen 2 are discussed.
Document ID
19760061726
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Driver, R. D.
(Harvard College Observatory and Smithsonian Astrophysical Observatory Cambridge, Mass., United States)
Snider, J. L.
(Harvard College Observatory and Smithsonian Astrophysical Observatory, Cambridge, Mass.; Oberlin College, Oberlin Ohio, United States)
Date Acquired
August 8, 2013
Publication Date
September 1, 1976
Publication Information
Publication: Astrophysical Journal
Volume: 208
Subject Category
Atomic And Molecular Physics
Accession Number
76A44692
Funding Number(s)
CONTRACT_GRANT: NGL-22-007-006
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available