The dynamics of the gas-phase reaction of H atoms with HCl has been studied experimentally employing the laser photolysis/vacuum-UV laser-induced fluorescence (LP/VUV-LIF) "pump-and-probe" technique and theoretically by means of quasiclassical trajectory (QCT) calculations performed on two versions of the new potential energy surface of Bian and Werner [Bian, W.; Werner, H.-J. J. Chem. Phys. 2000, 112, 220]. In the experimental studies translationally energetic H atoms with average collision energies of E col ) 1.4 and 1.7 eV were generated by pulsed laser photolysis of H 2 S and HBr at 222 nm, respectively. Ground-state Cl( 2 P 3/2 ) and spin-orbit excited Cl*( 2 P 1/2 ) atoms produced in the reactive collision of the H atoms with room-temperature HCl were detected under single collision conditions by VUV-LIF. The measurements of the Cl* formation spin-orbit branching ratio φ Cl* (1.4 eV) ) [Cl*]/[Cl + Cl*] ) 0.07 ( 0.01 and φ Cl* (1.7 eV) ) 0.19 ( 0.02 revealed the increasing importance of the nonadiabatic reaction channel H + HCl f H 2 + Cl* with increasing collision energy. To allow for comparison with the QCT calculations, total absolute reaction cross sections for chlorine atom formation, σ R (1.4 eV) ) (0.35 ( 0.16) Å 2 and σ R (1.7 eV) ) (0.13 ( 0.06) Å 2 , have been measured using a photolytic calibration method. In addition, further QCT calculations have been carried out for the H + DCl isotope reaction which can be compared with the results of previous reaction dynamics experiments of Barclay et al. [

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