Experimental and ab initio investigations of the kinetics of the reaction of H atoms with H2S

The rate constant k(1) for the H + H2S reaction has been measured from 298 to 598 K by the flash-photolysis resonance fluorescence technique, and the results are summarized as k(1) = (6.6 +/- 0.9) x 10(-11) exp[(-11.2 +/- 0.4 ) kJ mol(-1)/RT] cm(3) molecule(-1) s(-1)(1 sigma uncertainty in the parame ters). The 95% confidence interval for k(1) is estimated as 20%. Combinatio n with literature data reveals distinct curvature in the Arrhenius plot and a combined expression for 190-2237 K is k(1) = 5.8(-3.8)(+11.1) x 10(-17) T1.94+/-0.15 exp[(-455 +/- 67)/T] cm(3) molecule(-1) s(-1). The geometry, f requencies, and energy of the transition state were investigated at up to t he QCISD(T)/6-311+G(3df,2p) level of theory, and conventional transition st ate theory with Eckart tunneling corrections gave good accord with experime nt up to about 1000 K. Neglect of variational effects appears to lead to er rors of up to a factor of 2 at 2000 K.