Photoionization study of Fe(CO)5 and Ni(CO)4

Ph oto ioni za ti on yie ld c urves from onset to 600 A, a nd ionizati on threshold va lu es hav e been obta in ed for th e ions F'e(C O) .;, F e(C O ). ;, Fe(C O); 7, Fe(C O );, F e(C O )+, F e + a nd CO + from iro n pe ntac arbony l, a nd for N i(C O) i . N i(C O );t, N i(C O )l, N i(C O) +, Ni +, a nd CO + from nic ke l te tra ca rbonyl. From these c urv es, information on th e ioni za tion -fra gme nta ti on processes of F e(CO):, a nd Ni(CO)., und e r photon impa c t, ha ve bee n obta in ed. Diffe re nces in th e thres ho ld e ne rgies as dete rmin ed by photon a nd by elec tron imp act me thod s inc rease with th e fragme ntat ion. Th e a l) pea ran ce pote ntia ls and th e l1<"at s of formation of th e meta l-i o ns, a:rree within 0.1 e V, with th ose ca lc ul a ted from th e rmoc he mi ca l data . Th e ave rage bond di ssoc ia tion e nergy of th e ne utra l m olec ul e ag rees within 0.02 e V, with th e th e rm ochem ical valu es. Th e kin e ti c s hift for th e fo rmat ion of Fe -a nd N i ' ions is ve ry s mall. Th e N i ' ion is mos t lik ely form e d direc tl y from th e m olec ul e ion rathe r tha n by a cascad e fragme ntatio n process.