Study of the optical emission in Ne+Ne and Ar+Ar collisions in the range 15 to 500 eV

Apparent threshold energies have been measured for excitation of states of the configurations Ne(2p 5 3s), Ne(2p 5 3p), Ar(3p 5 4s) and Ar(3p 5 4p). The energy dependence of the cross sections for emission of radiation due to the decay of these states has been determined up to about 500 eV. Estimates are given for the absolute values of the cross sections in this range. The cross sections for excitation of different states arising from the same configuration Ne(2p 5 3p) or Ar(3p 5 4p) have different energy dependence at low energies; regular structure is found in the cross section ratio Q(2p 5 to 1s 3 )/Q(2p 1 to 1s 2 ) for Ne+Ne, and Q(2p 4 to 1s 3 )/Q(2p 1 to 1s 2 ;2p 5 to 1s 4 ) for Ar+Ar.