Origin of the “odd” behavior in the ultraviolet photochemistry of ozone

The origin of the even–odd rotational state population alternation in the16O2(a1Δg) fragments resulting from the ultraviolet (UV) photodissociation of16O3, a phenomenon first observed over 30 years ago, has been elucidated using full quantum theory. The calculated16O2(a1Δg) rotational state distribution following the 266-nm photolysis of 60 K ozone shows a strong even–odd propensity, in excellent agreement with the new experimental rotational state distribution measured under the same conditions. Theory indicates that the even rotational states are significantly more populated than the adjacent odd rotational states because of a preference for the formation of the A′ Λ-doublet, which can only occupy even rotational states due to the exchange symmetry of the two bosonic16O nuclei, and thus not as a result of parity-selective curve crossing as previously proposed. For nonrotating ozone, its dissociation on the excited B1A′ state dictates that only A′ Λ-doublets are populated, due to symmetry conservation. This selection rule is relaxed for rotating parent molecules, but a preference still persists for A′ Λ-doublets. The A′′/A′ ratio increases with increasing ozone rotational quantum number, and thus with increasing temperature, explaining the previously observed temperature dependence of the even–odd population alternation. In light of these results, it is concluded that the previously proposed parity-selective curve-crossing mechanism cannot be a source of heavy isotopic enrichment in the atmosphere.

Quantum interference in H + HD → H2 + D between direct abstraction and roaming insertion pathways

Understanding quantum interferences is essential to the study of chemical reaction dynamics. Here, we provide an interesting case of quantum interference between two topologically distinct pathways in the H + HD → H2 + D reaction in the collision energy range between 1.94 and 2.21 eV, manifested as oscillations in the energy dependence of the differential cross section for the H2 (v′ = 2, j′ = 3) product (where v′ is the vibrational quantum number and j′ is the rotational quantum number) in the backward scattering direction. The notable oscillation patterns observed are attributed to the strong quantum interference between the direct abstraction pathway and an unusual roaming insertion pathway. More interestingly, the observed interference pattern also provides a sensitive probe of the geometric phase effect at an energy far below the conical intersection in this reaction, which resembles the Aharonov–Bohm effect in physics, clearly demonstrating the quantum nature of chemical reactivity.

Channel-resolved rotationally dependent predissociation rate constants reveal the state-to-state dissociation dynamics of carbon monoxide in electronically excited states

Partial predissociation rate constants into each individual channel and their dependence on the rotational quantum number are obtained, revealing unprecedented details for the predissociation dynamics of CO.

Proof and Use of the Method of Combination Differences for Analyzing High-Resolution Coherent Multidimensional Spectra

High-resolution coherent multidimensional spectroscopy is a technique that automatically sorts rotationally resolved peaks by quantum number in 2D or 3D space. The resulting ability to obtain a set of peaks whose J values are sequentially ordered but not known raises the question of whether a method can be developed that yields a single unique solution that is correct. This paper includes a proof based upon the method of combined differences that shows that the solution would be unique because of the special form of the rotational energy function. Several simulated tests using a least squares analysis of simulated data were carried out, and the results indicate that this method is able to accurately determine the rotational quantum number, as well as the corresponding Dunham coefficients. Tests that include simulated random error were also carried out to illustrate how error can affect the accuracy of higher-order Dunham coefficients, and how increasing the number of points in the set can be used to help address that.

v-=SUB=-2-=/SUB=--зависимость вращательных вкладов в эффективный дипольный момент молекулы Н-=SUB=-2-=/SUB=-О и их влияние на уширение и сдвиг линий давлением буферных газов

The dependence of rotational correction terms of the effective dipole moment of H2O molecule on the vibrational quantum number v2 which corresponds to the large amplitude motion is obtained in the numerical calculations. Different dipole surfaces of H2O molecule as well as different intra-molecular potentials were used. The effect of the rotational corrections on the calculated line broadening and line shifts by Ar, Kr, H2 and He pressure was analyzed. It is shown that this effect is significant for a shifting of pure rotational lines and rovibrational lines for which the difference in rotational quantum number Ka from the initial and final states of the transition greater (or equal) to three.

High Temperature Optical Spectra of Diatomic Molecules at Local Thermodynamic Equilibrium

In the paper, several theoretical approaches to the determination of the reduced absorption and emission coefficients under local thermodynamic equilibrium conditions were exposed and discussed. The full quantum-mechanical procedure based on the Fourier grid Hamiltonian method was numerically robust but time consuming. In that method, all transitions between the bound, free, and quasi-bound states were treated as bound–bound transitions. The semi-classical method assumed continuous energies of ro-vibrational states, so it did not give the ro-vibrational structure of the molecular bands. That approach neglected the effects of turning points but agreed with the averaged-out quantum-mechanical spectra and it was computer time efficient. In the semi-quantum approximation, summing over the rotational quantum number J was done analytically using the classical Franck–Condon principle and the stationary–phase approximation and its consumption of computer time was lower by a few orders of magnitude than the case of the full quantum-mechanical approach. The approximation described well the vibrational but not the rotational structure of the molecular bands. All the above methods were compared and discussed in the case of a visible and near infrared spectrum of LiHe, Li2, and Cs2 molecules in the high temperature range.

Line broadening of SO2 and CO2 volcanic activity gases in the Earth’s atmosphere

Calculations of the CO2-broadening coefficients of sulfur oxide lines by the semi-empirical method [Mol. Phys. 102 (2004) 1653] and averaged energy difference method [Atmosph. Ocean. Optics 28 (2015) 403] are presented. In this work, 41 lines are considered, the rotational quantum number J varies from 14 to 51. Calculations of the line widths are carried out for room temperature (296 K), and also for the temperature range typical for the Ears atmosphere. There is good agreement with the literature data. The carbon dioxide lines broadening coefficients induced by nitrogen, nitrogen oxide, carbon monoxide and carbon dioxide at room temperature (T = 296 K) are obtained for a wide range of the rotational quantum number J (up to 100). The temperature exponents are calculated for every line widths. The calculations were performed by a semi-empirical method, based on the semiclassical impact theory of line broadening and modified by introducing additional correction factor whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data.

Calculation of Lambda Doubling for 7LiH1 molecule Using the System band emission for electronic transmissions

The A2?u-X1?g+ emission band system of 7LiH1 molecule has been calculated for Lambda doubling. The relation between wave number ?p , ?Q , ?R conducted the energies of the state of rotation F (J), and (J + 1) with rotational quantum number J, respectively, of 7LiH1 molecule for statehood A2?u using the rotation, fixed vibrational states of both the ground and raised crossovers vibrational against ???= 0 to V ' = 0-4using rotational levels J = 0 to J = 20 have found.

Determination and Study the Energy Characteristics of Vibrational-Rotational Levels and Spectral Lines of GaF, GaCl, GaBr and GaI for Ground State

A theoretical study of four gallium monohalides molecules (GaF, GaCl, GaBr and GaI) of ground state 1∑+ by using computer model is presented to study the energy characteristics of vibrational-rotational levels as a function of the vibrational and rotational quantum number , respectively. The calculations has been performed to examine the vibrational-rotational characteristics of some gallium halides molecules. These calculations appeared that all energies (Gv, Ev,J, and Fv,J) increase with increasing vibrational and rotational quantum number and by increasing the vibrational quantum number, and by increasing the vibrational quantum number, the vibrational constant will decrease. Also theoretical study of spectra of these molecules for ground state 1∑+ has been carried out. The values of spectral lines R(J) and P(J) were calculated and the relationship between the spectral lines and the rotational quantum number was established. The results appeared the spectra line values R(J) increases when the values of rotational quantum number decrease but the spectra line values P(J) decrease when the values of rotational quantum number increase, also the spectra line values P(J) decrease when the values of (m) increase, while the values of R(J) increase at first, then decrease showing Fortrar parabola.