Saddle-node bifurcations in the spectrum of HOCl

Abstract

Articles you may be interested inThe ultraviolet spectrum of OCS from first principles: Electronic transitions, vibrational structure and temperature dependence J. Chem. Phys. 137, 054313 (2012); 10.1063/1.4739756An ab initio potential energy surface and vibrational states of MgH 2 (1 1 A ′ )Highly excited vibrational states of HCP and their analysis in terms of periodic orbits: The genesis of saddle-node states and their spectroscopic signature A detailed analysis of the bound-state spectrum of HOCl ͑hypoclorous acid͒ in the ground electronic state is presented. Exact quantum mechanical calculations ͑filter diagonalization͒ are performed employing an ab initio potential energy surface, which has been constructed using the multireference configuration-interaction method and a quintuple-zeta one-particle basis set. The wave functions of all bound states up to the HOϩCl dissociation threshold are visually inspected in order to assign the spectrum in a rigorous way and to elucidate how the spectrum develops with energy. The dominant features are ͑1͒ a 2:1 anharmonic resonance between the bending mode and the OCl stretching mode, which is gradually tuned in as the energy increases, and ͑2͒ a saddle-node bifurcation, i.e., the sudden birth of a new family of states. The bifurcation is further investigated in terms of the structure of the classical phase space ͑periodic orbits, continuation/bifurcation diagram͒. It is also discussed how the spectrum of bound states persists into the continuum and how the various types of quantum mechanical continuum wave functions affect the state-specific dissociation rates.

Influence of Vibrational Resonances and Coriolis Coupling on Dissociation Rates in the Near-threshold Unimolecular Fragmentation of HOCl

“…The PES of the ground electronic state used in the present calculations has been fully described by Weiss et al [11]. In what follows energy is either measured with respect to the HO(r e ) ϩ Cl asymptote (eV) or the HO(n ϭ j ϭ 0) ϩ Cl dissociation threshold (cm Ϫ1 ).…”

“…[2] and [3]. A global PES for the ground electronic state of HOCl has been determined by largescale ab initio calculations by Skokov et al [18] and independently by Weiss et al [11]. Both surfaces are very similar to each other ; the one determined by Skokov et al [18] reproduces the experimental transition energies slightly better.…”

“…HOCl has a much higher density of states at threshold than HCO. None the less, HOCl is also characterized by a surprisingly large degree of regularity (i.e., assignability) [10,11].…”

“…For detailed discussions of the assignment and the anharmonic mixing between modes 2 and 3 at high energies see Refs. [10] and [11]. Most relevant for the study of unimolecular dissociation are the experiments of Sinha and coworkers [12Ϫ14] and Rizzo and coworkers [15Ϫ17].…”

“…In the present letter we report, using our PES [11], calculations for the decay of particular HOCl vibrational states and their dependence on the rotational quantum numbers employing the FD-CP method. When Coriolis coupling is neglected, the resonance widths are claimed to be converged within a factor of two or so for a particular K manifold.…”