States Of HBr Research Articles

Photo-double ionization of HBr and DBr studied by threshold photoelectrons coincidence spectroscopy

Photo-double ionization of HBr and DBr has been investigated in the 32–37 eV energy range using synchrotron radiation and the threshold photoelectrons coincidence (TPEsCO) method. The TPEsCO spectra of HBr and DBr, encompassing the formation of the X 3Σ −, a 1Δ and b 1Σ + states of HBr 2+ and DBr 2+, were recorded using a pair of penetrating-field electron spectrometers. All electronic band systems exhibited vibrational structure. In addition, the threshold photoelectron spectra of HBr and DBr for the formation of singly charged HBr and DBr were recorded simultaneously.

The ultrafast dynamics of HBr–water clusters: Influences on ion-pair formation

The ultrafast dynamics of HBr–water clusters have been investigated using pump–probe spectroscopy coupled with reflectron time-of-flight mass spectrometry. HBr clusters, mixed HBr–water clusters, and protonated water clusters are observed in the mass spectra. Dynamic studies reveal that when an HBr chromophore of a cluster with less than five solvent molecules is excited electronically, solvent reorganization occurs to form the solvent separated ion-pair [S. M. Hurley et al., Science 298, 202 (2002)]. The present paper focuses on the influence of clustering on the dynamics of the C and D states of HBr. In addition, further evidence is presented which confirms that complete dissolution of HBr requires five solvent molecules in the isolated species found in complexes comprised of pure water or HBr/H2O mixtures.

Dynamics of the E state of HBr and DBr: Evidence for the role of tunneling

The dynamics of the interaction of the Rydberg E(1Σ+) state and the valence state V(1Σ+) of HBr and DBr were investigated using a reflectron time-of-flight mass spectrometer coupled with a femtosecond laser system. Interrogation of the state formed by the avoided crossing of the Rydberg and valence states revealed dynamic behavior that was different for the two isotopes. Pump–probe experiments on HBr showed no change in the lifetime over the range of pump wavelengths of 256.7–254.7 nm. However, the lifetime of DBr decreased as the pump wavelength was tuned bluer. Tunneling is involved in the evolution of the population in photoexcited Rydberg state to the ion-pair state.

The predissociation dynamics of vibrational eigenstates in the A [formula omitted] state of HBr + ions: numerical solution of coupled time-dependent Schrödinger equations

The predissociation dynamics of the vibrational eigenstates of hydrogen bromide ions (HBr +) in the first excited electronic state A 2 Σ + which occurs via coupling to three repulsive ( 4 Σ − , 2 Σ − , and 4 Π ) states has been investigated by direct solution of four coupled time-dependent Schrödinger equations. The analysis shows multi-exponential decay for most of the predissociating vibrational states. The lifetime of these states decreases by several orders of magnitude from τ v=2 ≫1 ns to τ v=5 ≈17 fs. For even higher vibrational states lifetimes are increasing again up to the order of 100 fs. The contribution of the individual repulsive states to the predissociation dynamics is found to change as a function of time and of the vibrational level. The competition between the contributions of the repulsive states is most important during the first ∼10 fs. Beyond this one repulsive state in general dominates. Finally the shifting of vibrational `eigenenergies' of the A 2 Σ + state by spin–orbit interaction and their broadening due to the fast predissociation are analyzed.

Vibrational and rotational structure in the He I-excited photoelectron spectrum of the A 2 Sigma 1/2+ state of HBr+

Vibrational and rotational structure in the He I-excited photoelectron spectrum of the A 2 Sigma 1/2+ state of HBr+

Isotopic dependence of Born-Oppenheimer breakdown effects in diatomic hydrides: The X1Σ + states of [formula omitted] and [formula omitted

Line positions available from literature data for HI DI and HBr DBr have been employed to determine corrections to the Born-Oppenheimer approximation. For the ground X 1Σ + states of HI and DI, an analytical effective nonadiabatic Hamiltonian with 13 fitted parameters describes experimental observables within the precision of the measurements. The analytical operator for the X 1Σ + states of HBr and DBr is defined by 12 fitted parameters and achieves similar success. Rotational and centrifugal distortion constants are determined a posteriori through perturbation theory; along with the rotationless eigenvalues, they represent the spectroscopic line positions to within the precision of the measurements. Quantum-mechanical molecular constants are also calculated for TI, T 79Br, and T 81Br. A detailed study of the isotopic variation of R e values in hydrogen halide ground states is made using the existing theory.

Effect of vibrational excitation of HBr on the H+HBr abstraction and exchange reactions

The effect of vibrational excitation of HBr on the H+HBr→H2+Br and H+H′Br→H′+HBr reactions has been investigated on the extended LEPS surface (ELEPS) constructed on the basis of quantum chemically calculated points of PES. Together with this surface the LEPS surface of Sudhakaran and Raff [1] was used for comparison at two relative translational energies. A quasiclassical trajectory method was used to study the abstraction and exchange reaction dynamics. The reactive cross section was calculated as a function of the relative collision energy and the vibrational state of HBr. The following conclusions can be drawn from the results of the study: (i) vibrational excitation v=0→ v=2 more than doubles the reaction cross section, (ii) the increase in the collision energy is most effectively channelled into the product translational energy.

Electronic spectra and structure of the hydrogen halides: The [formula omitted] and [formula omitted] states of HBr and DBr

The absorption spectra of HBr and DBr below 1515 Å have been rephotographed at high resolution. Analyses of the “B”-X and C-X transitions show that the “B” and C states are the Ω = 1 components of a 3Π i (designated here as b) and a 1Π state, respectively. Both states originate from the same π 3 σ configuration. The coupling in these states is intermediate between Λ, S and Ω , ω and small tendencies toward Case c are present. Both the b and C states exhibit strong predissociations. Effective molecular constants are presented for the b and C states of HBr and DBr.

The absorption spectrum of gaseous hydrogen bromide in the Schumann region - II. Electronic states

The electronic states of HBr are discussed. The large number of states observed in the region 8·2 to 10·4 eV (part I) arise by the addition of an electron to the HBr + ( X 2 II i ) core. These are ‘highly excited’ states in which molecular orbitals derived from excited atomic orbitals are occupied. Coupling cases similar to those shown in the highly excited states of H 2 and of He 2 are envisaged, but the situation in HBr is complicated by the orbital angular momentum of the HBr + ion and by spin-orbit interaction. It is suggested that these coupling cases give rise to the unusual rotational structures observed in some of the absorption bands.