Absorption Line Width in Sodium Vapor

Abstract

Spectrograms of the D lines of sodium in absorption were obtained and measured on a densitometer, thus determining an optical constant which was uncertain in former work. Absolute contours in terms of transmitted intensity against wave-length were obtained. Possible sources of error were studied in detail. The observed contours were compared with the classical formula. The contours were found to have the theoretical inverse square variation of opacity with wave-length distance from resonance; they showed the theoretical variation of width with the square root of the number of atoms in the line of sight, and the 2:1 ratio between the two D lines. The width of the lines was, however, about five times that which classical radiation damping accounts for. A detailed further experimental study of this discrepancy is planned. GENERAL