Measured collisional radiative coefficients of the 4p groups of the argon I and argon II systems

Abstract We determine the r 1 ( p ) coefficients of the argon I 4p 1 P 1 state (2p 2 with Paschen notation) with the λ = 696.5 nm line and of the argon II 4p 2 D 5 2 state with the λ = 488.0 nm line in a highly ionized, low temperature ( T e = 3−4 eV ), magnetically confined (0.2 T) plasma of a hollow cathode arc with electron densities n e between 10 19 and 10 20 m −3 . The neutral density n 0 is 10 19 m −3 or less. The r 1 (4p) values are (6 ± 2) × 10 −5 for argon I and (5 ± 2) × 10 −4 for argon II.