Measurement of the electron-impact excitation rate coefficients from argon 1s states to 3p states

The apparent rate coefficients for the electron-impact excitation from argon 1s to 3p states are determined in the electron temperature (Te) range of 0.8 to 1.2 eV, in the afterglow of a capacitive argon discharge by using the temporal behavior of different state densities. The measured parameters include the densities of the 3p states (by optical emission), the densities of the four argon 1s states (by diode laser absorption) and Te (by a Langmuir probe and a line-ratio technique). Among the 24 rate coefficients obtained in this work, the results for excitation from the two resonance states (1s2 and 1s4) are reported here for the first time. As for the excitation from the two metastable states (1s3 and 1s5), the measured rate coefficients are compared with the available values from the distorted wave method and the electron beam experiment.