We report a potential energy surface and calculations of power spectra for ${\mathrm{CH}}_5^{+}.$ The potential surface is obtained by precise fitting of MP2/cc-pVTZ electronic energies and gradients, which are obtained in classical direct-dynamics calculations. The power spectra are obtained using standard microcanonical classical and novel quasiclassical calculations of the velocity autocorrelation function, from which the power spectrum is obtained in the usual way. Both calculations agree qualitatively that the overall spectrum is quite complex; however, the latter calculations indicate that some spectral features may be assignable.

We report a full dimensional, ab initio based potential energy surface for ${\mathrm{CH}}_5^{+}.$ The ab initio electronic energies and gradients are obtained in direct-dynamics calculations using second-order Møller-Plesset perturbation theory with the correlation consistent polarized valence triple zeta basis. The potential energy and the dipole moment surfaces are fit using novel procedures that ensure the full permutational symmetry of the system. The fitted potential energy surface is tested by comparing it against additional electronic energy calculations and by comparing normal mode frequencies at the three lowest-lying stationary points obtained from the fit against ab initio ones. Well-converged diffusion Monte Carlo zero-point energies, rotational constants, and projections along the CH and HH bond lengths and the tunneling coordinates are presented and compared with the corresponding harmonic oscillator and standard classical molecular dynamics ones. The delocalization of the wave function is analyzed through comparison of the ${\mathrm{CH}}_5^{+}$ distributions with those obtained when all of the hydrogen atoms are replaced by ${}^2\mathrm{H}$ and ${}^3\mathrm{H}.$ The classical dipole correlation function is examined as a function of the total energy. This provides a further probe of the delocalization of ${\mathrm{CH}}_5^{+}.$

The production of spin-polarized hydrogen atoms from the photodissociation of hydrogen chloride with circularly polarized 193-nanometer light is inferred from the measurement of the complete angular momentum distributions of ground state Cl( ² P _3/2 )and excited state Cl( ² P _1/2 )cofragments by slice imaging. The experimentally measured and ab initio predicted \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \(\mathbf{a}_{{\ }q}^{(k)}\) ( p )parameters, which describe the single-surface and multiple-surface-interference contributions to the angular momentum distributions, are in excellent agreement. For laser pulses longer than about 0.7 ns, the polarization of the electron and the proton are both 36%.

The photodissociation of jet-cooled IBr molecules has been investigated at numerous excitation wavelengths in the range 440–685 nm using a state-of-art ion imaging spectrometer operating under optimal conditions for velocity mapping. Image analysis provides precise threshold energies for the ground, $\mathrm{I}{(}^2{P}_{\text{3/2}}\mathrm{)+}\mathrm{Br}{(}^2{P}_{\text{3/2}}\mathrm{),}$ and first excited $[\mathrm{I}{(}^2{P}_{\text{3/2}}\mathrm{)+}\mathrm{Br}{(}^2{P}_{\text{1/2}}\mathrm{)]}$ dissociation asymptotes, the electronic branching into these two active product channels, and the recoil anisotropy of each set of products, as a function of excitation wavelength. Such experimental data have allowed mapping of the partial cross-sections for parallel (i.e., $\text{ΔΩ=0)}$ and perpendicular (i.e., $\text{ΔΩ=±1)}$ absorptions and thus deconvolution of the separately measured (room temperature) parent absorption spectrum into contributions associated with excitation to the ${\mathrm{A }}^3{\text{Π(1),\hspace{0.5em}B\hspace{0.05em}}}^3{\text{Π(0}}^{+})$ and ${}^1\text{Π(1)}$ excited states of IBr. Such analyses of the continuous absorption spectrum of IBr, taken together with previous spectroscopic data for the bound levels supported by the A and B state potentials, has allowed determination of the potential energy curves for, and (R independent) transition moments to, each of these excited states. Further wave packet calculations, which reproduce, quantitatively, the experimentally measured wavelength dependent product channel branching ratios and product recoil anisotropies, serve to confirm the accuracy of the excited state potential energy functions so derived and define the value (120 ${\mathrm{cm}}^{\text{−1}})$ of the strength of the coupling between the bound $\mathrm{(B)}$ and dissociative $\mathrm{(Y)}$ diabatic states of $0^{+}$ symmetry.