The Solid Phase Photolysis and Radiolysis of Ethylene at 20 to 77 K

Fi lms of e th ylen e conde nsed ont o a co ld fin ge r ma int a ine d a t 20 K we re ir radi a ted with photons whose e ne rgy ra nged fro m 8.4 to 21.2 e V. At the highe r ph oton e ne rgies th e re la tive yie lds of produc ts co mpa re we ll with those seen in th e radi o lys is of so lid e th yle ne. Expe rime nt s on C H2C D2 d e m ons tra te th a t in the photo lys is h ydrogen is ma inl y fo rm ed b y th e e limin a ti on processes CH2C D ~ ---> H AD 2) + C2D2(C 2H2) a nd C H,C D: ---> HD + C2HD. The re la tive proba bilities of th ese three pro-cesses a re inde pe nd e nt of th e e ne rgy of the in c ident photons from 8.4 to 11.6 e V a nd a re within expe rime nt a l error ide ntic a l to those obse rved in ea rl ie r gas phase photolys is expe rime nts . Re la t ive to ace tyle ne, cyc lobut a ne is a mi nor produc t a t 8.4 eV but inc reases by a n o rde r of magnit ud e a t hi ghe r e ne rgies whe re ions pla y a role. C yc lobuta ne , I ·bute ne a nd me th ylcyclopropa ne fo rmed upon irradia tion of frozen C 2H, C 2D, mixtures cons isted ma inl y of C,DB, C.,D,H" a nd C.,H 8. Pla us ib le mec ha ni sms wh ic h m ay acco unt fo r the fo rma tion of the la tt e r p roduc ts a re exa mine d. In t he so lid phase as in th e gas ph ase the re la ti ve importa nce of H·a tom product ion is seen to in crease with in c reas ing photon e ne rgy. Cyc lo propa ne, a ppa re ntl y formed b y in se rtion of C H, int o C, H." is obse rved as a produ c t a t a ll wave · le ngths in th e photo lys is, a nd in t he ra d io lys is.