An application of hypervirial perturbation theory to calculate energy eigenvalues of the Morse potential for various diatomic molecules

The Schrödinger equation with the potentialV(r)=D[exp(?2β(r?r _e))?2exp(?β(r?r _e))] is treated in the framework of the hypervirial-renormalization parameter scheme. The energy eigenvalues of various eigenstates for different molecules are calculated.     

A density functional theory and quantum theory of atoms in molecules study on hydrogen bonding interaction between paracetamol and water molecules

To consider the hydrogen bonding interactions between paracetamol and water molecules, probable complexes of paracetamol from three active sites (carbonyl oxygen atom, hydroxyl oxygen atom, and nitrogen atom) with H₂O molecule were formed. The optimized geometries and total energies have been obtained at the B3PW91/6-31+G(d, p) level of theory. Comparison of hydrogen bond lengths and the energies of complexes showed hydrogen bond that form between the oxygen atom of the carbonyl group and hydrogen atom is stronger than others. Moreover, an increase in the number of hydrogen bonds increases stability of paracetamol-water complexes. At the end, the QTAIM was applied to explain the nature of the hydrogen bonds and confirm the more stability by complexation.     

Time-dependent self-consistent perturbation theory and applications to molecules

The two most intense bands of the 370 nm electronic band system of tropolone have been rotationally analysed. They are separated by 18·93 cm^-1 and it has been shown that the high wavenumber band is the 0^--0^- (H₁ ¹) transition in what is almost certainly the internal hydrogen-bonding vibration v _H : the low wavenumber band is the 0⁺-0⁺ (0₀ ⁰) transition. A rotational contour analysis of both bands shows that there is an intensity alternation in K _a″ such that the ratio K _a″ even : odd is 10 : 6 in the 0⁺-0⁺ band and 6 : 10 in the 0^--0^- band. The intensity alternation, the nearly equal intensities of the 0⁺-0⁺ and 0^--0^- bands, the separation of these two bands and the anharmonic behaviour of v _H show that the separation of the 0⁺ and 0^- levels is small in the ground electronic state (probably less than 50 cm^-1) and is 18·93 cm^-1 larger in the excited electronic state.

The 0⁺-0⁺ and 0^--0^- bands are both type B showing that the electronic transition is à ¹ B ₂-X ¹ A ₁ and therefore π*-π rather than π*-n. The π*-n transition is probably shifted to high wavenumber by the internal hydrogen-bonding.     

A model of phase transitions in double-well Morse potential: Application to hydrogen bond

A model of phase transitions in double-well Morse potential is developed. Application of this model to the hydrogen bond is based on ab initio electron density calculations, which proved that the predominant contribution to the hydrogen bond energy originates from the interaction of proton with the electron shells of hydrogen-bonded atoms. This model uses a double-well Morse potential for proton. Analytical expressions for the hydrogen bond energy and the frequency of O–H stretching vibrations were obtained. Experimental data on the dependence of O–H vibration frequency on the bond length were successfully fitted with model-predicted dependences in classical and quantum mechanics approaches. Unlike empirical exponential function often used previously for dependence of O–H vibration frequency on the hydrogen bond length (Libowitzky, Mon. Chem., 1999, vol.130, 1047), the dependence reported here is theoretically substantiated.     

Quantum tunneling for separation of atoms and molecules from a mixture

We suggest a technique to separate specific types of isotopes, atoms, and molecules from a mixture. The mechanism is based on the tunneling phenomenon of slowly moving molecules released from a magneto-optical trap. We argue that the scheme suggested can be realized in the laboratory.     

Role of metastable atoms and molecules of helium in excitation transfer to hydrogen atoms

The afterglow of a discharge in helium with a small admixture of hydrogen is studied spectroscopically (p=40 Torr, [e]≤10¹¹ cm^?3). The time-resolved measurements of intensities of the first four lines of the Balmer series are performed. The concentrations of metastable helium atoms and molecules are evaluated from the relative intensity of the absorption lines. The ratios of excitation transfer rates from atoms He(2 ³ S ₁) k ₁(n) and molecules of helium He₂(a 2sσ ³Σ _u ⁺ ) k ₂(n) to atomic hydrogen H*(n) are measured to be k ₁(n=3)/k ₂(n=3)=0.04±0.02 and k ₁(n=4)/k ₂(n=4)=0.01±0.02. The ratios of excitation rate constants k ₂(n) corresponding to different states H(n) are measured to be k ₁(n=4)/k ₂(n=3)=0.023±0.01; k ₁(n=5)/k ₂(n=3)≤0.013; and k ₁(n=6)/k ₂(n=3)≤0.007.     

Corrections to the theory of screening and antiscreening in collisions with hydrogen atoms

By comparing with exact plane-wave-Born calculations of K-shell ionization in H + H collisions, a proposed correction to the theory of electron screening and antiscreening using the closure approximation is investigated.     

Quantum theory of electromagnetic fields interacting with atoms and molecules

This paper reviews the recent achievements in nonrelativistic quantum electrodynamics, especially nonlinear and coherent phenomena. The general properties of coupled radiation and matter are presented within simple models in section 1. The following sections treat in some detail three main aspects of the system and can be read independently of each other. Section 2 discusses some experiments with long-wave-length radiation (r.f.) and atoms. Section 3 presents the quantum theory of a laser and the ensuing photon distributions. Section 4 treats the case of strongly correlated emission of radiation called superradiance. The use of statistical ensembles is briefly discussed in Appendix A, whereas Appendices B, C and D present some technical details of the text.     

Quantum-chemical study of interaction of hydrogen atoms with graphene

The dependence of the binding energy and the activation energy of adsorption of hydrogen atoms on the number of previously adsorbed particles and their position—on one or both sides of a cluster, on nearest or distant neighbors (carbon atoms)—is investigated by quantum-chemical modeling. A hypothesis of the formation of adsorption sites (islands) on graphene at the initial stage of its saturation by hydrogen is discussed.     

Reactions of excited atoms and molecules with atoms and molecules

From a He-beam excited by electron impact we eliminated the He(2¹ S) component to better than 0.5% by irradiating light from a He discharge. The quenching process ishv(2¹ P→2¹ S)+He(2¹ S)→He(2¹ P)→He(1¹ S +hv) (2¹ P 1)¹ S. By measuring the ions produced in collisions of the He-metastables with various target gases in a mass spectrometer, singlet to triplet Penning-cross section ratios were obtained. These ratios are without exception close to one, which is taken as evidence for the previously proposed electron exchange mechanism of the Penning ionization. In the case that more ions are produced in the collision of He (2¹ S) and He(2³ S) with a target gas, separate relative production cross sections are obtained for the two metastables. For the rare gases the measurements are performed at two temperatures of the He-beam, 320 and 90 °K. It is found that the cross section ratio of associative — to Penning ionization increases considerably as the temperature is decreased for both, He(2¹ S) and He(2³ S), the effect being much more pronounced for He(2¹ S). The results of this work are found to confirm conclusions drawn from measured energy distributions of the electrons ejected in the Penning process.     

Reactions of excited atoms and molecules with atoms and molecules

Penning electron distributions arising from the ionization of Na and K by He (1s 2s ^1,3 S)-metastables in thermal collisions, as well as the absolute cross section for Penning ionization of Na by He (2³ S) and relative cross sections for ionization of Na and K by He(2¹ S) and He(2³ S) are measured. It is shown that under fairly general conditions the well depth ε* of the interaction potential between the metastable and the target particle can be obtained directly from the measured electron distributions. ε*-values are reported for the moleules He(1s 2s ^1,3 S)-Na(² S), K(² S) (^2,2Ω), and for He(1s 2s ^1,3 S)-Hg(¹ S)(^1,3Ω). These latter values are obtained from previously published measurements and are to be considered preliminary. Further, additional evidence is given, that Penning ionization with metastables is an electron exchange process.     

Reactions of excited atoms and molecules with atoms and molecules

Ionizing collisions of long lived excited particles with atoms and molecules are studied by a cross beam technique. For the first time reactions of atoms in high Rydberg states are included in the investigation. In this paper we report relative cross sections for the production of the ions RH⁺, RH ₂ ⁺ , and H ₂ ⁺ by collisions of excited rare gas atoms R^* with H₂. With HD as the target molecule the isotope effect for the production of RD⁺ and RH⁺ has been determined. In the case of argon and krypton, ions are produced only by the high Rydberg states, whereas in the case of helium and neon only the metastable states contribute to a measurable extent. The data indicate, that the reaction mechanism is different in principle for metastable and highly excited atoms. Simple models are proposed to explain the experimental results.     

O3与O3分子间相互作用的理论研究

采用从头算方法,在B3LYP水平下对O3分子单体及其二聚体进行了几何结构优化,得到四种O3分子二聚体的稳定构型,并经MP2法、均衡法(Massage)分别校正了电子相关和基组叠加误差(BSSE),通过对分子中原子间的最短距离,分子间质心距离与各构型相互作用能的关系进行了分析、比较,得到了最稳定的构型,其对应的O3分子二聚体相互作用能为:-8.788 kJ/mol.     

High-order perturbation theory for the hydrogen atom in a magnetic field

The states of a hydrogen atom with principal quantum numbers n⩽3 in a constant uniform magnetic field ℋ are studied. Coefficients in the expansion of the energy of these states in powers of ℋ² up to the 75th order are obtained. Series for the energies of the states and the wave functions are summed to values of ℋ on the order of the atomic magnetic field. A generalization of the moment method upon which these calculations are based can be used in other cases in which a hydrogen atom is perturbed by a potential with a polynomial dependence on the coordinates. Zh. éksp. Teor. Fiz. 113, 550–562 (February 1998)     

Stationary perturbation theory for atoms with two open shells in the Hartree-Fock approximation

Within the Hartree-Fock method, we have obtained equations of stationary “coupled” perturbation theory for multielectron systems with two open shells of different symmetry types (Huzinaga method) in the orbital representation. Corrections to the Hartree-Fock orbitals were determined in the form of expansions in unperturbed orbitals, which were calculated in the LCAO approximation in a basis of Slater-type atomic orbitals. Using an optimized basis set of atomic orbitals, we calculated the static polarizability for a number of atoms with two open shells. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 726–730, November–December, 2007.     

Formation of highly excited hydrogen atoms in a beam-foil interaction

The production of highly excited hydrogen atoms by passing a proton beam though a thin carbon foil has been investigated within the energy range 5–30 keV. The population of atoms in states with principal quantum number, n, between 14 and 25 have been determined using the field ionization technique and found to scale as n^?4.35±0.2.     

苯与PtH分子间电子相互作用的理论研究

采用从头算法在B3LYP水平分别对苯和PtH分子单体及其分子复合物体系(苯-PtH)进行了几何结构优化和振动频率计算,得到了3种苯-PtH分子复合物构型,研究了苯与PtH分子间相互作用对Pt-H键振动频率的影响,并得出了苯与PtH分子之间的相互作用能.