A KINETIC-MODEL FOR THE FORMATION OF AR-2 EXCIMERS

Argon up to pressures of 3 MPa was excited by intense electron beam pu mping. At the maximum an energy of 20 meV per atom was deposited into the gas. The population of the transient argon species Ar-2(+), Ar-3(), Ar-2(+)((3) Sigma(u)) and Ar-2((1) Sigma(u)) was investigated for different pumping conditions by absorption and emission spectrometry. A kinetic model is proposed that reproduces the experimental data. The spin-flip reaction Ar-2((3) Sigma(u)) --> Ar-2*((1) Sigma(u)) with a rate constant of 5 x 10(-8) cm(3) s(-1) is responsible for the rapid destruction of the metastable Ar-2((3) Sigma(u)) excimer and for the population of the lasing Ar-2((1) Sigma(u)) state. The rapid dissocia tion of vibrationally excited Ar-2((3) Sigma(u)) by plasma electrons leads to a saturation in the population of Ar-2((1) Sigma(u)) with ri sing pumping density.