The 4s ← 1b1 and 3d ← 1b1 Rydberg states of H2O and D2O: Spectroscopy and predissociation dynamics

Two new electronic states of H2O and D2O have been identified in the energy range 84 000–88 000 cm−1 as three-photon resonances in four-photon ionization spectroscopy. Simulations of the rotational intensity distributions using asymmetric top three-photon line strength theory, and rotational analyses, characterize the states as B1 and A2. These Rydberg states are assigned to the excitations 4sa1 ← 1b1[Formula: see text] and 3d2 ← 1b1[Formula: see text] on the basis of equilibrium geometries, quantum defects, and the polarization dependence of their three-photon transition probabilities. The identification of the one-photon forbidden 1A2–1A1 transition, together with published vacuum ultraviolet (VUV) absorption spectra, permits a consistent assignment for all five members of the 3d ← 1b1 complex.The [Formula: see text] and [Formula: see text] states arc predissociatcd via both homogeneous and heterogeneous mechanisms. The homogeneous channel from the [Formula: see text] state shows a dramatic isotope effect, being about two orders of magnitude faster in H2O than from equivalent levels of D2O. The heterogeneous predissociation exhibits irregular vibronic and isotopic dependencies, which can be rationalized in terms of the intercessional role of accidental near resonances with levels of the heavily predissociated [Formula: see text] state. The (000) levels of the [Formula: see text] states of H2O and D2O show contrasting heterogeneous predissociation behaviour, which can be interpreted with a knowledge of the relevant potential energy surfaces and the electronic–rotational Coriolis interactions that couple the states.

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Potential Energy Surfaces for Reactions of X Metal Atoms (X = Cu, Zn, Cd, Ga, Al, Au, or Hg) with YH4 Molecules (Y = C, Si, or Ge) and Transition Probabilities at Avoided Crossings in Some Cases

Advances in Physical Chemistry ◽

10.1155/2012/720197 ◽

2012 ◽

Vol 2012 ◽

pp. 1-17 ◽

Cited By ~ 4

Author(s):

Octavio Novaro ◽

María del Alba Pacheco-Blas ◽

Juan Horacio Pacheco-Sánchez

Keyword(s):

Excited State ◽

Excited States ◽

Metal Atom ◽

Potential Energy Surfaces ◽

Transition Probabilities ◽

Metal Atoms ◽

Avoided Crossings ◽

Reaction Barriers ◽

Energy Surfaces

We review ab initio studies based on quantum mechanics on the most important mechanisms of reaction leading to the C–H, Si–H, and Ge–H bond breaking of methane, silane, and germane, respectively, by a metal atom in the lowest states in symmetry: X(2nd excited state, 1st excited state and ground state) + YH4 H3XYH H + XYH3 and XH + YH3. with X = Au, Zn, Cd, Hg, Al, and G, and Y = C, Si, and Ge. Important issues considered here are (a) the role that the occupation of the d-, s-, or p-shells of the metal atom plays in the interactions with a methane or silane or germane molecule, (b) the role of either singlet or doublet excited states of metals on the reaction barriers, and (c) the role of transition probabilities for different families of reacting metals with these gases, using the H–X–Y angle as a reaction coordinate. The breaking of the Y–H bond of YH4 is useful in the production of amorphous hydrogenated films, necessary in several fields of industry.

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Ultraviolet spectroscopy of pressurized and supercritical carbon dioxide

Communications Chemistry ◽

10.1038/s42004-021-00516-z ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Timothy W. Marin ◽

Ireneusz Janik

Keyword(s):

Carbon Dioxide ◽

Potential Energy Surfaces ◽

Vacuum Ultraviolet ◽

Electronic Absorption Spectra ◽

Industrial Applications ◽

Ultraviolet Spectroscopy ◽

Collisional Broadening ◽

Thermodynamic Critical Point ◽

State Potential ◽

Energy Surfaces

AbstractCarbon dioxide (CO2) is prevalent in planetary atmospheres and sees use in a variety of industrial applications. Despite its ubiquitous nature, its photochemistry remains poorly understood. In this work we explore the density dependence of pressurized and supercritical CO2 electronic absorption spectra by vacuum ultraviolet spectroscopy over the wavelength range 1455-2000 Å. We show that the lowest absorption band transition energy is unaffected by a density increase up to and beyond the thermodynamic critical point (137 bar, 308 K). However, the diffuse vibrational structure inherent to the spectrum gradually decreases in magnitude. This effect cannot be explained solely by collisional broadening and/or dimerization. We suggest that at high densities close proximity of neighboring CO2 molecules with a variety of orientations perturbs the multiple monomer electronic state potential energy surfaces, facilitating coupling between binding and dissociative states. We estimate a critical radius of ~4.1 Å necessary to cause such perturbations.

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THEORETICAL TRANSITION PROBABILITIES FOR THE $\tilde{A}^{2}A_{1} -\tilde{X}^{2}B_{1}$ SYSTEM OF H2O+ AND D2O+ AND RELATED FRANCK–CONDON FACTORS BASED ON GLOBAL POTENTIAL ENERGY SURFACES

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633605001428 ◽

2005 ◽

Vol 04 (01) ◽

pp. 225-245 ◽

Cited By ~ 1

Author(s):

IKUO TOKUE ◽

KATSUYOSHI YAMASAKI ◽

SATOSHI MINAMINO ◽

SHINKOH NANBU

Keyword(s):

Potential Energy ◽

Photoelectron Spectroscopy ◽

Potential Energy Surfaces ◽

Least Squares Method ◽

Transition Probabilities ◽

Three Dimensional ◽

Equilibrium Geometry ◽

Condon Factors ◽

Energy Surfaces ◽

Franck Condon

To elucidate the ionization dynamics, in particular the vibrational distribution, of H 2 O +(Ã) produced by photoionization and the Penning ionization of H 2 O and D 2 O with He *(2 3S) atoms, Franck–Condon factors (FCFs) were given for the [Formula: see text] ionization, and the transition probabilities were presented for the [Formula: see text] emission. The FCFs were obtained by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of [Formula: see text] and [Formula: see text] electronic states. The global PESs were determined by the multi-reference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard interpolation. The obtained FCFs exhibit that the [Formula: see text] state primarily populates the vibrational ground state, as its equilibrium geometry is almost equal to that of [Formula: see text], while the bending mode (ν2) is strongly enhanced for the H 2 O +(Ã) state; the maximums in the population of H 2 O + and D 2 O + are approximately v2 = 11–12 and 15–17, respectively. These results are consistent with the distributions observed by photoelectron spectroscopy. Transition probabilities for the [Formula: see text] system of H 2 O + and D 2 O + show that the bending progressions consist primarily of the [Formula: see text] emission, with combination bands from the (1, v′2 = 4–8, 0) level being next most important.

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A QM/MM Study of Acylphosphatase Reveals the Nucleophilic-Attack and Ensuing Carbonyl-Assisted Catalytic Mechanisms

10.26434/chemrxiv.11984448.v1 ◽

2020 ◽

Author(s):

zheng zhao ◽

Phil bourne ◽

Hao Hu ◽

Huanyu Chu

Keyword(s):

Energy Barrier ◽

Potential Energy Surfaces ◽

Catalytic Mechanism ◽

Interaction Networks ◽

Nucleophilic Attack ◽

Reaction Coordinates ◽

Transition State Stabilization ◽

Catalytic Mechanisms ◽

Energy Surfaces

Acylphosphatase is one of the vital enzymes in many organs/tissues to catalyze an acylphosphate molecule into carboxylate and phosphate. Here we use a combined <i>ab initio</i> QM/MM approach to reveal the catalytic mechanism of the benzoylphosphate-bound acylphosphatase system. Using a multi-dimensional reaction-coordinates-driving scheme, we obtained a detailed catalytic process including one nucleophilic-attack and then an ensuing carbonyl-shuttle catalytic mechanism by calculating two-dimensional potential energy surfaces. We also obtained an experiment-agreeable energy barrier and validated the role of the key amino acid Asn38. Additionally, we qualified the transition state stabilization strategy based on the amino acids-contributed interaction networks revealed in the enzymatic environment. This study provided usefule insights into the underlying catalytic mechanism to contribute to disease-involved research.

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