Experimental and ab Initio Investigations of the Kinetics of the Reaction of H Atoms with H 2 S

The rate constant k 1 for the H + H 2 S 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) × 10 -11 exp[(−11.2 ± 0.4) kJ mol -1 / RT ] cm 3 molecule -1 s -1 (1σ uncertainty in the parameters). The 95% confidence interval for k 1 is estimated as 20%. Combination with literature data reveals distinct curvature in the Arrhenius plot and a combined expression for 190−2237 K is k 1 = 5. × 10 -17 T 1.94±0.15 exp[(−455 ± 67)/ T ] cm 3 molecule -1 s -1 . The geometry, frequencies, and energy of the transition state were investigated at up to the QCISD(T)/6-311+G(3df,2p) level of theory, and conventional transition state theory with Eckart tunneling corrections gave good accord with experiment up to about 1000 K. Neglect of variational effects appears to lead to errors of up to a factor of 2 at 2000 K.