Multiphoton ionization of molecules under the conditions of strong field-induced perturbation of Rydberg states

Multiphonon ionization of the H₂ molecule under the action of a weak (probe) field, which provides the initial population of the low-lying (working) level, and intense monochromatic linearly polarized radiation is studied. The multiphoton ionization process occurs under the conditions of strong field perturbation of two intermediate Rydberg series, np0(¹Σ _u ⁺ and np2(¹Π_u), of the optical R(0)branch which have different ionization potentials. The series are occupied simultaneously as a result of single-photon absorption by an excited H ₂ ^* molecule in the working state 4s σH′¹Σ _g ⁺ (v=0). As a result of the irregularity in the arrangement of the intermediate levels from a large group of states that are combined in the multiphoton ionization process a sharp and irregular change occurs in the dependence of the shifts and widths Γ_n of the levels on the intensity f of the strong field in a transition from one level to another. It is shown that for field intensities f such that the level widths remain much less than the splitting between the levels (Γ_n≪/n ³) the stabilizing effect (i.e., the field-induced narrowing of the levels as f→∞) in the form Γ_n ∝ 1/f ² (as happens in atoms with a structureless core) is not observed in molecular systems. Zh. éksp. Teor. Fiz. 115, 1987–2000 (June 1999)     

Role of structural elements of chloronaphthalene molecules in spin-orbit coupling: Phosphorescence

The dipole moments (P ^s ) of the T ₁ ^S → S ₀ transition from the triplet sublevels s = z, y, x, which are determined by the spin-orbit (SO) coupling, are studied for a series of mono- and dichloro derivatives of naphthalene. Based on the model calculations, the effects of different factors (SO coupling in individual chlorine atoms occupying the α and β positions in the molecule, SO coupling in the carbon backbone of the molecule, and the compensation effect caused by the interference of SO interactions in individual structural elements of the molecule) on P ^s are differentiated and discussed.     

Calculation of the quenching rate constants for electronically excited singlet molecular nitrogen

The quenching rate constants for the singlet states (a′)⁽¹⁾Σ _u ⁻ (v = 1−17), a ⁽¹⁾Π _g (v = 0−14), and w ⁽¹⁾Δ _u (v = 0−13) of molecular nitrogen colliding with an N₂ molecule are calculated using quantum-chemical approximations. It is shown for the first time that both the intramolecular and intermolecular processes of electronic excitation transfer are significant for these states. Calculated rate constants are in satisfactory agreement with experimental data.     

VO分子2Δ3/2-12Δ3/2电子跃迁P线系发射谱线的研究

本文利用孙卫国课题组建立的能精确计算(预言)某双原子分子电子态P线系发射谱线的物理新公式, 首次研究了VO分子从电子态²Δ_3/2跃迁到电子态1²Δ_3/2的(0, 0)跃迁带中的P线系发射谱线. 获得的研究结果不仅重复了实验上已知的低转动态谱线数据,而且还正确预言了该跃迁带在 实验上难以精确测量的转动量子数J=80.5以内的高振转激发态的P线系发射光谱. 为研究VO分子内部结构提供了重要的物理信息.     

Small Exotic Molecules with Bosonic Constituents

We study the stability and the properties of the ground state of neutral systems containing up to four positively charged bosons and their antiparticles. Examples are the di-pionium molecule (π ⁺ π ⁻)², which is almost identical to the positronium molecule (e ⁺ e ⁻)², the tri-pionium (π ⁺ π ⁻)³, and the quadri-pionium (π ⁺ π ⁻)⁴ molecules. We briefly compare our results on the energy to those on the large-N limit of (π ⁺ π ⁻) ^N . We also show that the annihilation probability can be calculated accurately with simple wave functions when one uses the generalized Schwinger rule. Received September 5, 1994; accepted for publication October 15, 1994     

Microhydration of the methylene blue cation in an electrospray ion source

Microhydrated methylene blue cations, MB⁺(H₂O) _n , are produced in an electrospray ion source and their size-distributions are measured as a function of the source temperature. A series of MB⁺(H₂O) _n ions is observed up to n ≃ 60. A striking feature observed in the mass spectra is that the series of hydrated ions starts at n = 4; intensities of n = 1–3 are extremely suppressed. The absence of n = 1–3 ions is well explained by the energetics concerning evaporation processes of water molecules, based on stable structures and the binding energies of MB⁺(H₂O) _n ions calculated by DFT calculations up to n = 5. MB⁺(H₂O) _n ions for n > 4 evaporate a single water molecule sequentially, while MB⁺(H₂O)₄ tends to fragment into MB⁺ and (H₂O)₄ rather than MB⁺(H₂O)₃ and an H₂O molecule. We have observed a clear magic peak at n = 24, which strongly suggests that the MB⁺(H₂O)₂₄ ion is formed by attaching a neutral (H₂O)₂₀ cage onto an MB⁺(H₂O)₄ ion.     

Hall coefficient in solution for a simple dynamical model

A model Liouville equation is proposed for a system composed of an ion moving in a solvent fluid. Using this model, explicit results are obtained for the Ohmic conductivityL and the Hall conductivityh. These results are then used to calculate the Hall coefficientR = ehL^–2, which is a measure of the effect of non-Brownian motion, for several charge carriers of interest. Our results are in agreement with earlier findings based on a stochastic model which predictR > 1 for H⁺(aq). Our results also indicate thatR 1 for charge carriers such as Na⁺, Cl^–, and K⁺ which have a mass greater than that of a solvent molecule (here taken as 18 amu).This research was supported in part by grants from the National Science Foundation and by the Research Foundation of the State University of New York.     

Measurement of the nuclear magnetic moment of tritium to nine-digit accuracy

A series of ten pair spectra has been obtained by simultaneously detecting the proton and tritium NMR spectra of the gaseous TH sample, which is an analogue of molecular hydrogen. The numerical processing of the data yields the ratio F(TH)/F(HT) = 1.066 639 8933(7) of the magnetic moments of tritium and proton in the TH molecule. The relative statistical error of this result is 7 × 10⁻¹⁰. To find the nuclear magnetic moment of tritium from F(TH)/F(HT), it is sufficient to use the previously calculated correction factor δ = (1 + 20.4 × 10⁻⁹), which originates from a small asymmetry of the electron cloud of the molecule.     

Ab Initio Calculations on the Tricarbon Monoxide Molecule C3O

The six-dimensional potential energy surface of the ground state X¹Σ⁺ of C₃O has been generated by the CCSD(T) approach. The spectroscopic constants of this molecule are calculated and the vibrational spectrum is derived. The fundamentals are accurate to within 10 cm⁻¹ compared to the available experimental data. The ground state correlates to the closed shell C₂(X¹Σ⁺_g)+CO(X¹Σ⁺) dissociation limit. The bonding in this molecule can be explained by charge transfer from CO to C₂. The lowest electronic excited states are also investigated.     

Theoretical study of NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> interacting with carbon nanotube

This paper deals with quantum mechanical interaction of no ₃⁻ with (5,5) and (8,0) swcnts. To perform this we have made an ab initio calculation based on the density functional theory. In these framework the electronic density plays a central role and it was obtained of a self-consistent field form. It was observed through binding energy that NO₃⁻ molecule interacts with each nanotube in a physisorption regime. We propose these swcnts as a potential filter device due to reasonable interaction with NO₃⁻ molecule. Besides this type of filter could be reusable, therefore after the filtering, the swcnts could be separated from NO₃⁻ molecule.      

Nuclear fusion in the mesic molecule d μ 3He

A new scheme is presented for the physical processes leading to the nuclear fusion reaction d(³He, ⁴He)p catalyzed by a negatively charged muon μ⁻. It is shown that the observable rate and yield of the nuclear reaction depend on a chain of ion-molecular reactions involving the participation of the dμ ³He molecule. New calculations of the nuclear fusion rates in the dμ³He molecule are presented. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 89–94 (25 January 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Temperature dependence of Rb2 molecule formation rate constant in a magneto-optical trap

In this paper, we report the measurement of Rb₂ molecule formation rate constant due to a two body process in a magneto-optical trap as a function of the sample temperature. The ground state molecules are detected by two-photon ionization, through the intermediate a ³Σ _u ⁺ → 2³Π _g molecular band. Our results show that the Rb₂ molecules formed in the MOT could be due to a wave shape resonance, which enhances the molecule formation rate. This effect may be used to enhance the molecule production; and therefore it maybe important to future experiments involving production and trapping of cold ground state molecules.     

Electronic spectrum of cobalt doped rubidium zinc sulphate hexahydrate

Optical absorption spectrum of Co²⁺ doped rubidium zinc sulphate hexahydrate has been investigated both at room and at liquid nitrogen temperatures. The gross features of the observed spectrum are characteristic of octahedral symmetry associated with spin-orbit interaction. The interelectronic repulsion (B, C), crystal field (Dq) and spin-orbit () parameters which give a good fit to the observed band positions areB = 860 cm^–1,C = 3870 cm^–,Dq = 980 cm^–1,= 500 cm^–1. The non-ligand bands observed in the spectrum are attributed to vibrational modes of water molecule.The authors are thankful to the Council of Scientific and Industrial Research, New Delhi (India) for financial support.     

Analysis of the High-Resolution Infrared Spectrum of the PHD2 Molecule: ν1 and 2ν1 Bands

The results of investigation into the infrared spectra of the PHD₂ molecule including the ₁ fundamental band centered at 2324.005 cm^–1 (with a resolution of 4.2·10^–3 cm^–1) and the first 2₁ valence overtone centered at 4563.634 cm^–1 (with a resolution of 8.8·10^–3 cm^–1) are given in the present paper. Based on an analysis of the results obtained, 1340 and 1020 lines are referred to the ₁ and 2₁ bands, respectively. This data are used to calculate 316 and 248 vibrational-rotational energies of the (100000) and (200000) excited vibrational states, respectively. Since both bands can be considered as isolated, we take advantage of the Watson Hamiltonian (the reduction A in the I ^r representation) to describe their rotational structure. The calculated spectroscopic parameters of the examined states of the PHD₂ molecule correlate well with each other and with the corresponding parameters of the ground vibrational state.     

The electronic structure of KMnO4 investigated by photoemission and electron-energy-loss spectroscopy

From photoemission and electron-energy-loss data the following picture of KMnO₄, with Mn^VII (with a formal charge state Mn⁷⁺ (3d ⁰)) tetrahedrally surrounded by four O^2–-ions, is deduced: strong covalent bonding between Mn^VII and O^2– leads to a considerable occupation of the Mn-3 d shell. The ground state of the (MnO₄)^–1 molecule is an orbital and spin singlet as seen by the absence of any multiplet splitting in the Mn core levels. The valence band shows a four peak structure extending form 4 eV to 8 eV below the Fermi energy. The first peak at 4.2 eV has mainly O-2p character. The remaining peaks are of strongly mixed Mn-3d/O-2p character due to the covalent bonding. This mixing decreases with increasing binding energy. The electron energy loss data show a variety of structures between 2 eV and 10 eV independent of the primary electron energy which defines them as dipole allowed charge-transfer transitions. An additional excitation at 1.8 eV decreases quickly in intensity with increasing electron energy which classifies it as a dipole or spin forbidden transition in the compound. This energy is close to the value of 1.6 eV reported for the activation energy observed in electrical transport data. The results are compared to quantum chemical molecular orbital calculations of the (MnO₄)^–1 molecule.Physics Department, Allahabad University Allahabad 211002, India     

The π ← n transition of formic acid

New sharp bands of formic acid have been observed in the near ultraviolet at the long wave-length end of the previously observed diffuse band system (2250–2500 Å) by considerably extending the absorption path length. Both the diffuse and sharp bands belong to the same vibrational system which is assigned to the π^* ← n electronic transition in the carbonyl group. Extensive progressions are observed in the carbonyl stretching frequency which is greatly reduced in the excited state (fundamental ν₃′ ≈ 1080 cm⁻¹) and many intervals of about 400 cm⁻¹ are assigned to the OCO bending frequency ν₇′.A band contour analysis of the 2593 Å band shows that the molecule is nonplanar in the excited state because of the magnitude and sign of the inertial defect. From this analysis, the rotational constants for the excited state are S^‘=1.8755, B^‘0.4042, C^‘=0.3378cm⁻¹ By the plausible assumption that the important changes in the molecule are in the C=0 bond length, the OCO angle, and the nonplanarity due to the formyl hydrogen, the following excited state parameters are derived.rC=0 = 1.407A.The changes in formic acid are closely analogous to the changes in formyl fluoride as a result of the π^* ← n transition.     

CARS study of the vibrational kinetics of nitrogen molecules in the burning and afterglow stages of a pulsed discharge

The vibrational kinetics of the nitrogen molecule in the ground state X ¹Σ _g ⁺ in the burning and afterglow stages of a pulsed discharge are investigated by coherent anti-Stokes Raman spectroscopy (CARS). The total cross section for vibrational excitation of the nitrogen molecule by electron impact to the first eight vibrational levels is determined. The rate constant for the associative ionization reaction involving nitrogen atoms in the metastable states ² P and ² D is estimated. It is found that the best agreement between the calculated and measured populations of the nitrogen molecules in the ground state X ¹Σ _g ⁺ in the afterglow stage of a pulsed discharge is obtained when the rate constant for VV exchange K ₀₁ ¹⁰ has the value predicted by the quantum-classical Billing-Fisher model. Zh. Tekh. Fiz. 67, 34–42 (May 1997)     

Polarized fluorescence of jet-cooled molecular iodine

The degree of polarized fluorescence of molecular iodine ¹²⁷I₂ cooled in a supersonic jet under rotationally selective excitation in the electronic transition B ³Π_0u ⁺-X ¹Σ _g ⁺ has been measured and calculated. It was found that the interaction of the angular momentum of the molecule with the nuclear spins of iodine atoms leads to a considerable depolarizing effect. This effect is most pronounced for small rotational quantum numbers of the angular momentum that are comparable with the total nuclear spin of the iodine molecule, which is equal to 5.     

V2-dependence of centrifugal constants of H2O molecules in the Morse oscillator model

It is shown in this paper that the centrifugal constantsC ^l (t) calculated in the Morse, oscillator model for the sequence from the operator H _red ^(t) , which is used in processing the rotational levels of the H₂O molecule, are linked by recurrence relations, which enables H _z ^(t) –H _z ^(O) to be given in closed form.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 56–58, October, 1982.