Measurement of Potassium Number Density Using Molecular Absorption

Abstract

The absorption cross section of the B¹Π_u-X¹Σ⁺_g·(610-720 nm) and C¹Π_u-X¹Σ⁺_g(400-470 nm) band system of K₂ has been determined experimentally in K-Ar mixtures. Absorption spectra of the band system were measured at a gas temperature of 773 K and gas pressures from 10 to 1000 kPa. The number density of K was measured using the total absorption of the 5p-4s resonance lines and number density of K₂ was determined from the equilibrium relation. It has been found that the absorption coefficient of the band system is smoothened by collision broadening of the lines in the band system and becomes constant at pressures greater than 200 kPa. The effects of the gas temperature and the slit function on the absorption cross section are evaluated theoretically.