ABSOLUTE RATE CONSTANTS OF R+NO(+M)-]RNO(+M) REACTIONS .2. MEASUREMENTS FOR R=C2F5, I-C3F7, N-C4F9, AND T-C4F9 AT T=295-K

Absolute rate constants of the reactions C2F5+NO(+M)-->C2F5NO(+M) (4), i-C3F7+NO(+M)-->i-C3F7NO(+M) (5), n-C4F9+NO(+M)-->n-C4F9NO(+M) (6) and t-C4F9+NO(+M)-->t-C4F9NO(+M) (7) for M = He over the pressure range 10-500 Torr have been measured at T = 295 K by means of time-resolved intracavity absorption of He-Ne laser radiation combined with excimer laser flash photolysis. The fall-off curves k([M]) have been constructed using a procedure based on Troe's formalism. The limiting high-pressure rate constants obtained are k4,infinity = (1.8+/-0.2) X 10(-11) cm3/s, k5,infinity = (1.7+/-0.2) X 10(-11) cm3/s, k6,infinity = (1.6+/-0.2) X 10(-11) cm3/s and k7,infinity = (1.25+/-0.20) X 10(-11) cm3/s. A statistical adiabatic channel model (SACM) calculation of k(infinity) for the R+NO-->RNO reaction has been performed for several radicals R. Experimental k(infinity) values are described by SACM with 0.50<alpha/beta<0.62.