Broadening of the I2P1/2 > P3/2 Transition Lineshape by Unsteady Vortex Motion (Postprint)

摘要

The spectroscopically measured lineshape of an atomic transition provides a wealth of useful information relative to diagnosing The use of atomic transition lineshapes to ascertain the temperature of a gas stems to the 1920s, particularly within the astronomical community. Indeed, this community was the first to recognize the potential contribution of large scale bulk motion of the gas to the breadth of the spectroscopic measurement of transition lineshapes beyond that of the random molecular motion associated with temperature. In 1934 Stuve and Elvey showed that by including a bulk gas velocity Doppler broadening term in the Voigt equation for the transition lineshape in addition to the random thermal motion term, it was possible to estimate whether a stellar atmosphere was turbulent or not based upon the fit of the Voigt equation to the measured transition lineshapes for that atmosphere. Taking the theory a step further, using estimated optical paths or length scales for the stellar atmospheres that they were measuring, they were able to estimate median gas velocities and correlate increasing velocity magnitude with increasing temperature of the stellar atmosphere based upon the Voigt fit.