'The dissociation by electron-impact of 8F6, CF 4, and 8 iF4 has bee n studied with a consolidated mass spectrometer . Data are a lso given on t he appearance potentia ls of various ions in t.he mass spectra and measure ments on the isotope abundance of s ulfur, carbon, and s ilico n. 'The observed appearance potent ia ls of t he 1"+ ion in 81"6 and CF4, and the C+ ion in CF4 were found to be lower t han t he calcu lated value ass umin g formation of a positive atom ion and a free electro n, but nearl y oq ual to the calculated value ass um ing t he formation of a positive atom ion a nd a negati ve fluo rin e ion . The large rela tive abunda nce of t he 81"4++ ion in 81"6 and t he CF2++ ion in CF4 is take n to indi oate the form atiO n of t hose ions by removal of two 1"-ions in the f ormor a nd possib ly an 1"-iun a nd a free e lectron in t he latter case.

R elativc 'l,bundances an d a ppearance potential s a re reported for positive a nd negativ e i on~ obse rved in CF4, CF3CI, CF3Br, a nd CF3I. The kin etic-energy distribution of pos itive ions is obtain ed by means of a " bealIl-d eAection" tech niqu e. These da ta combin ed with that of recent t hermochem ical a nd spectroscop ic studies perm it a n ew calcu lation of t he io ni;l;ation potential of the CF3 r ad ical of 9.3 ± O.2 electron volts, as well as estimates of fluorocarbon bond-dissociation energies. The energeties of probablc di ssociation processC's are di~c u sse d.

The fou r d euteromethan e have been sy nthesized and t heir mass spect ra ob tain ed w ith a Consolidat.ed mass spectrometer. The se nsitivities of t he molecu le ions of CH , a nd o f CD, are eq ual wi thin t he estimated un certainty. The total ionization is the same fo r CH " CHaD, and CHzD z but is signifi ca ntly Jow for C D ,. The m ass spectra of the de ute romet ha nes ar e not predictable from CH, by statistical co nsiderations alone. In agreem e nt with pre viously p ublished data o n CH aD , p robabili ty fac to rs of 1.18 and 0.45 we re obse rv ed for t he cLi ssoc iation of an H atom or a D atom compared wi th t he dissociation of an H atom from CH •. \Vhereas these facto rs re main a pproximately constant for subsequent dissociations in the sam e molec ule, they differ markedly for th e t hree protiodeu tero methanes. ' Vide diverge nce is obser ved for some probabili ty factors obtained in di ssociatio ns of two or more atoms.

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