1st and 2nd order contributions to the double ionization of argon resulting from positron and electron impact

Angular dependences for electron emission resulting from single and double ionization of argon are presented for 200, 500, and 1000 eV positron and electron impact. From these data, double to single ionization ratios are determined as a function of the emission direction. At each impact energy, these ratios have different angular dependences positive and negative particle impact. The positron and electron induced ratios are analyzed to provide information about how first- and second-order double ionization mechanisms interfere and contribute to the differential electron emission.