Multiconfiguration self-consistent field quadratic response calculations of the two-photon transition probability rate constants for argon

Abstract
The two-photon transition probability rate constant for the transition from the ground state (1Se) to the 1De excited state of argon has been calculated by the means of multiconfiguration self-consistent field quadratic response methods. The rate constant for the 1De transition in the Hartree–Fock approximation is 0.119×10−50 cm4 s, while in the multiconfiguration Hartree–Fock calculation it is 0.191×10−50 cm4 s. The calculated rate constant is in an excellent agreement with the experimental rate constant of 0.205×10−50 cm4 s obtained as the sum of the rate constants for the transitions to the spin–orbit mixed 3p54p[3/2]J=2 (1De), 3p54p[5/2]J=2 (3De), and 3p54p′[3/2]J=2 (3Pe) states.