Pressure broadening and shift rates for Ar (s–p) transitions observed in an Ar–He discharge

Abstract

The pressure broadening and shift rates have been measured for the 801.699nm (s5→p8), 800.836nm (s4→p6) and 795.036nm (s3→p4) transitions in argon perturbed by 10–200Torr of helium and argon at a temperature of 440±20K using a radio-frequency, capacitively coupled discharge. For a 10% Ar in He plasma the pressure broadening and shift rates were measured as 14.18±0.65 and 1.81±0.30MHz/Torr, 17.85±0.78 and 0.72±0.32MHz/Torr, and 16.59±1.22 and 2.94±0.48MHz/Torr for the 801.699nm, 800.836nm and 795.036 nm transitions, respectively. The influence of the slightly varying gas temperature on the broadening and shift rates is less than 1%. Stark broadening and shifting by electrons in the discharge are not measurable due to low electron densities and temperatures. Phase-changing collisional cross-sections in the literature decrease with temperature, in good agreement with the Lindholm–Foley T−0.2 trend based on the Lennard–Jones potential. Further investigation of the Ar⁎–Ar and Ar⁎–He interaction potentials is necessary to understand the behavior of the cross sections.