Inclusive. pi. /sup -/ production with 200 MeV protons: Radiochemical study of the /sup 209/Bi(p,. pi. /sup -/xn)/sup 210-x/ At reactions

The results of a radiochemical study of the /sup 209/Bi(p,..pi../sup -/xn)/sup 210-x/At reactions for x = 0 to 5 are reported. 200 MeV protons were utilized in an investigation of these pion production reactions as well as secondary processes such as /sup 209/Bi(p,/sup 3,4/He)X followed by /sup 209/Bi(/sup 3,4/He,xn)/sup 213-x/ At. The relative importance of such secondary reactions was reduced through variation of the target thickness and from a survey of available data from on-line investigations of /sup 3,4/He production by other medium energy proton-induced reactions on /sup 209/Bi. An inclusive cross section of 48 +- 13 ..mu..b is determined for the /sup 209/Bi(p,..pi../sup -/xn)/sup 210-x/At reactions at 200 MeV. The relative yields of such (p,..pi../sup -/xn) products are found to be suggestive of a pion production mechanism involving ..pi../sup -/ emission through coherent interactions with the target nucleons.