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

- Ar-He (s-p) pressure broadening and shift rates are measured in an RF discharge.
- Temperature dependent broadening cross-sections agrees with Lindholm-Foley theory.
- Helium induces a blue shift, while argon is red shifted.
- An atmospheric pressure discharge would be sufficient for diode pumped rare gas laser.

The pressure broadening and shift rates have been measured for the 801.699 nm (s5→p8), 800.836 nm (s4→p6) and 795.036 nm (s3→p4) transitions in argon perturbed by 10-200 Torr 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 801.699 nm, 800.836 nm 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.