Determination of the electron-impact transfer rate coefficients between the Ar(1s) states in an afterglow discharge

Electron-impact transfer rate coefficients, from Ar(1s₅) to Ar(1s₄) and from Ar(1s₃) to Ar(1s₂), are obtained in the afterglow of a capacitive discharge. The discharge is generated by a pulsed 13.56 MHz rf power source with 20 mTorr argon. The densities of the four argon 1s states are measured by diode laser absorption, the electron temperature (T_e) is measured by a Langmuir probe and the electron density is measured by both the probe and a microwave interferometer. Using the measured parameters and a kinetic model for Ar metastable states in the afterglow, the electron-impact transfer rate coefficients are determined in a T_e range of 0.25−1.0 eV. It is found that the obtained rate coefficients agree well with those from the R-matrix calculation. (paper)