scholarly journals Sunlight-Initiated Photochemistry: Excited Vibrational States of Atmospheric Chromophores

2008 ◽  
Vol 2008 ◽  
pp. 1-13 ◽  
Author(s):  
Veronica Vaida ◽  
Karl J. Feierabend ◽  
Nabilah Rontu ◽  
Kaito Takahashi
Keyword(s):  
Solar Radiation ◽  
Electronic State ◽  
Chemical Bond ◽  
Wavelength Range ◽  
Chemical Reactions ◽  
Energy Barrier ◽  
Bond Energies ◽  
Vibrational States ◽  
Vibrational Levels ◽  
Combination Bands

Atmospheric chemical reactions are often initiated by ultraviolet (UV) solar radiation since absorption in that wavelength range coincides to typical chemical bond energies. In this review, we present an alternative process by which chemical reactions occur with the excitation of vibrational levels in the ground electronic state by red solar photons. We focus on the O–H vibrational manifold which can be an atmospheric chromophore for driving vibrationally mediated overtone-induced chemical reactions. Experimental and theoretical O–H intensities of several carboxylic acids, alcohols, and peroxides are presented. The importance of combination bands in spectra at chemically relevant energies is examined in the context of atmospheric photochemistry. Candidate systems for overtone-initiated chemistry are provided, and their lowest energy barrier for reaction and the minimum quanta of O–H stretch required for reaction are calculated. We conclude with a discussion of the major pathways available for overtone-induced reactions in the atmosphere.

Convergence Properties of Quasiclassical Trajectory Calculations on Dynamics of Autoionization Event in He(23S)-D2 Penning Ionization

1997 ◽  
Vol 62 (2) ◽  
pp. 154-171 ◽  
Author(s):  
Jan Vojtík ◽  
Richard Kotal
Keyword(s):  
Branching Ratios ◽  
Classical Trajectory ◽  
Vibrational States ◽  
Penning Ionization ◽  
Trajectory Calculations ◽  
Quantum Mechanical Treatment ◽  
Total Ionization ◽  
Vibrational Levels ◽  
Degree Of Convergence ◽  
Product Branching

An analysis of the degree of convergence of theoretical pictures of the dynamics of the autoionization event He(23S)-D2(v" = 0) -> [He...D2+(v')] + e is presented for a number of batches of Monte Carlo calculations differing in the number of the trajectories run. The treatment of the dynamics consists in 2D classical trajectory calculations based on static characteristics which include a quantum mechanical treatment of the perturbed D2(v" = 0) and D2+(v') vibrational motion. The vibrational populations are dynamical averages over the local widths of the He(23S)-D2(v" = 0) state with respect to autoionization to D2+(...He) in its v'th vibrational level and the Penning electron energies are related to the local differences between the energies of the corresponding perturbed D2(v" = 0)(...He*) and D2+(v')(...He) vibrational states. Special attention is paid to the connection between the requirements on the degree of convergence of the classical trajectory picture of the event and the purpose of the calculations. Information is obtained regarding a scale of the trajectory calculations required for physically sensible applications of the model to an interpretation of different type of experiments on the system: total ionization cross section measurements, Penning ionization electron spectra, subsequent 3D classical trajectory calculations of branching ratios of the products of the postionization collision process, and interpretation of electron ion coincidence measurements of the product branching ratios for individual vibrational levels of the nascent Penning ion.

Energies and Electric Dipole Moments of the Bound Vibrational States of HN2+ and DN2+

2008 ◽  
Vol 73 (6-7) ◽  
pp. 873-897 ◽  
Author(s):  
Vladimír Špirko ◽  
Ota Bludský ◽  
Wolfgang P. Kraemer
Keyword(s):  
Dipole Moment ◽  
Nearest Neighbor ◽  
Energy Surface ◽  
Dipole Moments ◽  
Three Dimensional ◽  
Vibrational States ◽  
Spacing Distribution ◽  
Triatomic Molecules ◽  
Vibrational Levels ◽  
Different Levels

The adiabatic three-dimensional potential energy surface and the corresponding dipole moment surface describing the ground electronic state of HN2+ (Χ1Σ+) are calculated at different levels of ab initio theory. The calculations cover the entire bound part of the potential up to its lowest dissociation channel including the isomerization barrier. Energies of all bound vibrational and low-lying ro-vibrational levels are determined in a fully variational procedure using the Suttcliffe-Tennyson Hamiltonian for triatomic molecules. They are in close agreement with the available experimental numbers. From the dipole moment function effective dipoles and transition moments are obtained for all the calculated vibrational and ro-vibrational states. Statistical tools such as the density of states or the nearest-neighbor level spacing distribution (NNSD) are applied to describe and analyse general patterns and characteristics of the energy and dipole results calculated for the massively large number of states of the strongly bound HN2+ ion and its deuterated isotopomer.

Vibration-rotation bands and rotational constants of dideuteroacetylene

1955 ◽  
Vol 232 (1190) ◽  
pp. 291-309 ◽  
Keyword(s):  
Resolving Power ◽  
Vibrational States ◽  
Absorption Bands ◽  
Rotational Constants ◽  
Vibrational Assignments ◽  
Vibrational Anharmonicity ◽  
A Value ◽  
Vibrational Levels ◽  
Vibration Rotation ◽  
Very High

Nine vibrational absorption bands of dideutero-acetylene have been examined with very high resolving power. The rotational constants have been determined for the vibrational levels concerned, and the coefficients α i have been determined with more convincing accuracy than previously. In some of the bands the Q branches have been resolved, so that the l -doubling coefficients q i could be derived, and details could be established about the doublet components in some II levels. The results emphasize the need of high resolution if the vibrational assignments are to be unambiguous, and if reliable values of the rotational constants are to be derived. A value of B e has been obtained, and the vibrational anharmonicity coefficients have been considered briefly. Estimates of the centrifugal stretching constants D i in different vibrational states have been made, and one anomalous case has been found.

scholarly journals The interaction of atoms and molecules with solid surfaces - X-The activation of adsorbed atoms by metallic electrons

1937 ◽  
Vol 163 (912) ◽  
pp. 101-127 ◽  
Keyword(s):  
Vibrational State ◽  
Simple Calculation ◽  
Solid Surfaces ◽  
Adsorbed Atom ◽  
Vibrational States ◽  
Free Electrons ◽  
Atoms And Molecules ◽  
Vibrational Levels ◽  
Adsorbed Atoms ◽  
Thermal Vibrations

One object of this series of papers (Lennard-Jones and others 1935-7) is to consider in detail the mechanism of condensation, migration and evaporation of atoms and molecules at solid surfaces and to try to find the processes which govern the transition from one state to another. It has been shown that under certain conditions the thermal vibrations of a solid may activate an adsorbed atom from one vibrational state to a higher one or even eject it from the surface altogether. But the theory there developed is limited in the sense that it deals only with the transfer of single quanta to or from the solid, and consequently the quantized vibrational levels of the adsorbed atom must be closer together than the largest single quantum of energy which the solid can emit. An attempt has been made (Strachan 1937) to find the probability of the simultaneous emission or absorption of several quanta by the solid, and the indication is that the probability of several such simultaneous events is small. Now when atoms are bound to solid surfaces by valency forces, the vibrational levels are widely spaced compared with those of the solid, and many thermal quanta must be transferred simultaneously to the adsorbed atom to change its state of vibration. While this process may occur in nature, it seemed desirable to look for other possible processes whereby adsorbed atoms could be activated to higher vibrational states. One such possible mechanism, in metals at any rate, is by the transfer of energy from the conduction electrons. A simple calculation by classical methods indicates that in a typical case a surface atom may suffer as many as 10 15 collisions per second with the “free” electrons of a metal, and as, according to modern views, these electrons are moving with an energy of several volts, there is here an ample reservoir of energy from which adsorbed atoms may absorb energy or to which they can re-emit it, and thus change their vibrational state, or indeed, also their electronic state.

scholarly journals Model of daytime emissions of electronically-vibrationally excited products of O<sub>3</sub> and O<sub>2</sub> photolysis: application to ozone retrieval

2006 ◽  
Vol 24 (11) ◽  
pp. 2823-2839 ◽  
Author(s):  
V. A. Yankovsky ◽  
R. O. Manuilova
Keyword(s):  
Atomic Oxygen ◽  
Energy Exchange ◽  
Electronic States ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Proposed Model ◽  
Vibrational Levels ◽  
Electronically Excited ◽  
Basic Facts ◽  
Kinetics Of

Abstract. The traditional kinetics of electronically excited products of O3 and O2 photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O2(a1Δg, v) and O2(b1Σ+g, v), excited atomic oxygen O(1D), and the O2 molecules in the ground electronic state O2(X3Σg−, v). In contrast to the previous models of kinetics of O2(a1Δg) and O2 (b1Σ+g), our model takes into consideration the following basic facts: first, photolysis of O3 and O2 and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b1Σ+g, a1Δg and X3Σg−; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O2(b1Σ+g, v=0) (at 762 nm) and O2(a1Δg, v=0) (at 1.27 µm), but also leads to populating the excited electronic–vibrational states O2(b1Σ+g, v=1) and O2(b1Σ+g, v=2) (at 689 nm and 629 nm). The proposed model allows one to calculate not only the vertical profiles of the O2(a1Δg, v=0) and O2(b1Σ

scholarly journals Quantum computation solves a half-century-old enigma: Elusive vibrational states of magnesium dimer found

2020 ◽  
Vol 6 (14) ◽  
pp. eaay4058 ◽  
Author(s):  
Stephen H. Yuwono ◽  
Ilias Magoulas ◽  
Piotr Piecuch
Keyword(s):  
Ground State ◽  
State Of The Art ◽  
Coupled Cluster ◽  
Experimental Investigations ◽  
Experimental Characterization ◽  
Vibrational States ◽  
Vibrational Levels ◽  
State Potential ◽  
Derived Data ◽  
Important System

The high-lying vibrational states of the magnesium dimer (Mg2), which has been recognized as an important system in studies of ultracold and collisional phenomena, have eluded experimental characterization for half a century. Until now, only the first 14 vibrational states of Mg2 have been experimentally resolved, although it has been suggested that the ground-state potential may support five additional levels. Here, we present highly accurate ab initio potential energy curves based on state-of-the-art coupled-cluster and full configuration interaction computations for the ground and excited electronic states involved in the experimental investigations of Mg2. Our ground-state potential unambiguously confirms the existence of 19 vibrational levels, with ~1 cm−1 root mean square deviation between the calculated rovibrational term values and the available experimental and experimentally derived data. Our computations reproduce the latest laser-induced fluorescence spectrum and provide guidance for the experimental detection of the previously unresolved vibrational levels.

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