High resolution spectroscopy of the ns' autoionizing resonances in Ar

Abstract
The 3p5ns'( 1/2 )0.1 autoionizing resonances of argon have been investigated using a two-step excitation from the 3p54s(3/2)1.2levels (1s4 and 1s5 in Paschen's notation) populated in a discharge. Most of the levels of J=0 had never been observed previously. The absorption profiles have been recorded by means of a sensitive optogalvanic detection. Energy position and width data have been obtained for n ranging from 11 to 34. Our experimental values allow a precise redetermination of the second ionization limit I1/2 and show that the width Gamma 0 of the J=0 level is larger than the width Gamma 1 of the corresponding J=1 level. We find I1/2=128 541.41+or-0.07 cm-1and Gamma 0/ Gamma 1=1.6+or-0.2, respectively.