Determination of the Rate Constants for the Radical-Radical Reactions NH2((X)over-tilde2B1) + NH(X3Σ-) and NH2((X)over-tilde2B1) + H(2S) at 293 K

The rate constant for the reactions NH2((X) over tilde B-2(1)) + NH(X-3 Sigma) and NH2((X) over tilde B-2(1)) + H(S-2) were measured over a pressure range from 2 to 10 Torr in CF4, or Ar gases at 293 +/- 2 K. The radicals were produced by the 193 nm photolysis of NH3 dilute in the carrier gas. Both radicals were monitored simultaneously following the photolysis laser pulse using high-resolution time-resolved absorption spectroscopy. The NH2 radical was monitored using the (1)2(21) <- (1)3(11) rotational transition of the (0,7,0)(A) over tilde (2)A(1) <- (0,0,0) (X) over tilde B-2(1) vibronic band near 675 nm, and the NH radical was monitored using the R-1(3)(4) rotational transition on the 1-0 vibrational transition near 3084 nm. The data was analyzed using model simulations of the NH2 and NH temporal concentration profiles. The rate constants for the NH2 + NH and NH2 + H reactions were found to be (9.6 +/- 3.2) x 10(-11) and (7.7 +/- 14) x 10(-15) cm(3) molecule(-1) s(-1), respectively, where the uncertainty includes an estimate of both systematic and random errors. The measurements were independent of the nature of the diluents, CF4 or Ar, and total pressure.