The ground and first excited singlet states of monochlorosilylene have been reexamined using pulsed discharge jet and laser induced fluorescence techniques. HSiCl and DSiCl have been produced by an electric discharge through SiHCl3 and SiDCl3 vapor in argon. The 000 band rotational constants of four isotopomers of HSiCl and the harmonic force fields for both states have been combined to obtain the following estimates of the equilibrium structures: r′′(SiCl)=2.067(3) Å, r′′(SiH)=1.525(5) Å, θ′′(HSiCl)=96.9(5)°, r(SiCl)=2.040(3) Å, r(SiH)=1.532(8) Å, and θ(HSiCl)=118.1(5)°. Previous anomalies in the ground-state structure and the excited-state vibrational frequencies have been resolved. The radiative lifetime of the 480–400 nm (Ã 1A′′–X̃ 1A) band system of HSiCl has been measured to be 432±20 ns.

Mechanism of the reaction, CH 4 +O ( 1 D 2 )→ CH 3 +OH , studied by ultrafast and state-resolved photolysis/probe spectroscopy of the CH 4 O 3 van der Waals complex Quantum state-resolved reactive scattering of F+H 2 in supersonic jets: Nascent HF (v,J) rovibrational distributions via IR laser direct absorption methods J. Chem. Phys. 109, 9306 (1998); 10.1063/1.477592State-to-state reactive scattering of F+H 2 in supersonic jets: Nascent rovibrational HF (v,J) distributions via direct IR laser absorption State-to-state reactive scattering of FϩCH 4 →HF(v,J)ϩCH 3 is studied using crossed supersonic jets and high-resolution (⌬Ϸ0.0001 cm Ϫ1 ) IR laser direct absorption techniques. Rovibrational state-resolved HF column-integrated absorption profiles are obtained under single collision conditions and converted to populations via appropriate density-to-flux transformation. Nascent rovibrational distributions in each HF(v,J) state are reported. Summed over all product rotational levels, the nascent vibrational quantum state populations for HF(v) ͓(vϭ3) 0.106(3); (v ϭ2) 0.667 (14); (vϭ1) 0.189 (27); (vϭ0) 0.038(78); 2 error bars͔ are in agreement with previous flow cell studies by Setser, Heydtmann, and co-workers ͓Chem. Phys. 94, 109 ͑1985͔͒. At the rotational state level, however, the current studies indicate nascent distributions for HF(v,J) that are significantly hotter than previously reported, ostensibly due to reduced collisional relaxation effects under supersonic jet conditions. Final HF rotational states from FϩCH 4 are observed near the maximum energetically accessible J values in both the vϭ2 and vϭ3 vibrational manifolds, which provides experimental support for a bent F-H-C transition state structure.

Exothermic reactive scattering of F atoms at the gas-liquid interface of a liquid hydrocarbon (squalane) surface has been studied under single collision conditions by shot noise limited high-resolution infrared absorption on the nascent HF(v,J) product. The nascent HF(v,J) vibrational distributions are inverted, indicating insufficient time for complete vibrational energy transfer into the surface liquid. The HF(v=2,J) rotational distributions are well fit with a two temperature Boltzmann analysis, with a near room temperature component (T(TD) approximately equal to 290 K) and a second much hotter scattering component (T(HDS) approximately equal to 1040 K). These data provide quantum state level support for microscopic branching in the atom abstraction dynamics corresponding to escape of nascent HF from the liquid surface on time scales both slow and fast with respect to rotational relaxation.