The study of ungerade electronic states of the Xe2 molecules in the region of Xe*(5p 56p, 5d, 7s, 6d) by the resonance multiphoton ionization method

Electronic spectra of the Xe2 molecules in the energy range of 77700?C89300 cm^?1 are recorded. The method of resonance enhanced multiphoton ionization of molecules in a supersonic molecular beam was used, in which excitation of the molecules by three photons was followed by ionization caused by a fourth photon (the (3+1) REMPI method). Analysis of the vibrational structure of observed systems of bands yielded information about the dissociation energy and the molecular constants for ungerade states of molecules. On the basis of the Franck-Condon principle, the equilibrium distances for potential curves were estimated from the relative intensities in vibrational progressions. Data on 16 new electronic states of diatomic xenon molecules with the dissociation limits Xe ₂ ^* ?? XE(5p ^{6 1} S ₀) + Xe*(5p ⁵6p,5d, 7s, 7p) were obtained.     

Comment on: “Universal relation between spectroscopic constants”

Kaur and Mahajan [1] have claimed to derive a universal relation InG = 1.91578(±0.09727) + 0.97111(±0.03809) In Δ between the Sutherland parameter Δ(=ω _er _e ² /2D_e) and the dimensionless parameterG(= 8ω _ex_e/B_e) for the ground as well as excited electronic states of diatomic molecules. Validity of this relation is checked and we find that the relation is not correct. Next, we checked the validity of the relation Δ = 2.2r_e for the alkali group diatomic molecules. This relation is also found not to be correct.     

六参数高精度双原子分子解析势能函数

提出一种构造解析势能函数的新方法,得到一种六参数解析势能函数,该势能函数适用于多种基本类型的双原子分子.用同核中性基态双原子分子Li₂-X¹Σ_g⁺、Na₂-X¹Σ_g⁺,异核带电基态双原子分子离子(BC)^--X³∏,异核中性激发态双原子分子PbS-A¹Σ⁺、BaO-A¹Σ,异核带电激发态双原子分子离子(CS)⁺-A²∏,同核中性激发态双原子分子K₂-B¹∏_u,同核带电激发态双原子分子离子N₂⁺-B²Σ_u⁺等共36个算例对该势能函数进行验证,计算结果与RKR(Rydberg-Klein-Rees)数据或振动能谱实验数据高精度符合.同时发现,在分子振动能谱计算精度方面,该势能函数总体上优于Murrell-Sorbie势能函数.     

Rotational structures of long-range diatomic molecules

We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with -C _n /r ⁿ (n > 2) asymptotic interaction can have only 1, 2, and up to a maximum of n-2 rotational levels. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to different atom-atom scattering properties above the dissociation limit.Received: 15 June 2004, Published online: 28 September 2004PACS: 33.15.Mt Rotation, vibration, and vibration-rotation constants - 34.10. + x General theories and models of atomic and molecular collisions and interactions (including statistical theories, transition state, stochastic and trajectory models, etc.) - 03.75.Nt Other Bose-Einstein condensation phenomena - 03.75.Ss Degenerate Fermi gases     

普适性双原子分子解析势能函数的研究

提出了一种构造解析势能函数的新方法,由此得到了一种既适用于中性双原子分子又适用于带电双原子分子离子的解析势能函数。本文用八种基本类型的双原子分子——同核中性基态双原子分子Na₂-X1Σ+_g,同核中性激发态双原子分子C₂-A1Π_u,同核带电基态双原子分子离子He+₂-X2Σ+_u,同核带电激发态双原子分子离子N+₂-B2Σ+_u,异核中性基态双原子分子NaLi-X1Σ+_g,异核中性激发态双原子分子BH-B1Σ+,异核带电基态双原子分子离子(BC)--X3Π,异核带电激发态双原子分子离子(CS)+-A2Π等共21个算例对势能函数进行了验证并与RKR (Rydberg-Klein-Rees)实验数据进行了比较,计算结果与RKR数据符合很好。     

O~+ + H_2及其同位素取代反应的立体动力学研究

运用准经典轨线方法,基于RODRIGO势能面,对碰撞能为20kcal/mol时,O++H2及其同位素取代反应的立体动力学性质进行了理论研究,对k-j′两矢量相关和k-k′-j′三矢量相关的分布函数、极化微分反应截面,以及产物转动取向参数进行了详细的讨论.结果表明,O++H2→OH++H,O++DH→OD++H和O++TH→OT++H反应的立体动力学性质对体系的质量因数非常敏感.     

Exact solutions for vibrational levels of the Morse potential via the asymptotic iteration method

Exact solutions for vibrational levels of diatomic molecules via the Morse potential are obtained by means of the asymptotic iteration method. It is shown that the numerical results for the energy eigenvalues of⁷Li₂ are all in excellent agreement with those obtained before. Without any loss of generality, other states and other diatomic molecules could be treated in a similar way.     

双荷电双原子分子的新解析势能函数

提出了能更好反映双荷电双原子分子势能曲线特点的新解析势能函数，并推导出了相应的二、三、四阶力常数计算公式；作为新函数的应用实例，给出了BH2+, He22+ 和HF2+等分子离子的解析势能函数，力常数和光谱数据。     

The Near-Infrared YΣ-XΠ Transition of CuSe

The near-infrared Y²Σ⁺-X²Π transition of the diatomic molecule CuSe was observed for the first time. A King-type carbon tube furnace was used to produce the gas phase of the CuSe molecules. The Fourier transform spectrometer associated with the National Solar Observatory, Kitt Peak, Arizona was used to record the molecular emission spectrum in the region 9850-12 400 cm⁻¹. A vibronic analysis and comparisons of the spin-orbit constant and the ²Σ⁺ transition energy to those for related isovalent molecules are presented.     

Radial Functions of Diatomic Lithium Halides X 1Σ+ From Vibration-Rotational Spectra

The radial functions for potential energy and adiabatic and nonadiabatic effects in the forms of polynomials with coefficients c_j, h_j ^Li, h_j ^X, g_j ^Li and g_j ^X of the reduced variable for internuclear distance z=2.(R-R_e)/(R+R_e) to various non-negative powers have been determined for the family of diatomic molecules of the lithium halides, LiF, LiCl, LiBr and LiI, with the corresponding results of LiH included for purposes of comparison. Trends are evident in the coefficients of lower order, but those of higher order are susceptible not only to the influence of the extent and quality of the data but also to the truncation of the power series in the representations. The various radial functions are valid with the specified ranges of internuclear distance depending on the maximum extent of vibrational excitation of the spectra.     

Universal basis of two-center functions. test computations of certain diatomic molecules and ions

It is shown that the basis of two-center functions is universal. The dependence of the nuclei of atoms comprising a molecule on charges and on the intranuclear spacing is separated explicitly in the integrals used in analyzing diatomic molecules. The basis integrals constructed once permitted rapid and effective execution of computations for the ground state potential curves for a number of electron systems: H₂, He₂ ²⁺, HeH⁺, He₂, LiH, Li₂, HeB⁺, Be₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 74–79, November, 1986.     

Comparison of the ground state vibrational fundamentals of diatomic molecules in the gas phase and in inert solid matrices

Despite the voluminous literature on the spectra of diatomic molecules, there are many gaps in our knowledge of their ground state vibrational frequencies. For many important diatomic molecules, only values obtained in matrix isolation experiments are available. In order to assess the likely extent of deviation of the ground state $\text{ΔG(}\text{1}\text{2}\text{)}$ values of diatomic molecules observed in rare-gas and nitrogen matrices from the gas-phase values, a systematic comparison has been made between gas-phase and matrix frequencies. The dependence of matrix shifts on the matrix material and type of chemical bond is considered for the approximately 230 pairs of observations, spanning the entire Periodic Table, which have been reported. Except for van der Waals molecules and for the Group Ia and IIIa halides, the argon-matrix shift for most diatomic molecules is less than 2%.     

Determination of the helium-4 mass in a Penning trap

The determination of the rotational quadrupole alignment of diatomic molecules via REMPI detection is investigated. In this process a high focal intensity usually increases the detection probability. At high intensities the AC Stark effect may cause a splitting of the normally degenerate m_J sublevels of a rotational state J beyond the spectral width of the exciting radiation. This leads to a selective detection of only certain m_J states with the consequence that deduced alignment factors can be misleading. From the theoretical considerations line profiles are explicitly calculated for dynamic polarizabilities which represent the B ¹Σ⁺ _u←X ¹Σ⁺ _g transition of H₂, in order to fit an experimental (3+1) REMPI spectrum and to predict (1+1') line shapes as a function of laser intensity. It is further shown that the deduced quadrupole alignment factor A ₀ ⁽²⁾ is significantly changed by the second order AC Stark effect when the intensities are chosen high enough to observe asymmetric broadened line profiles. Different combinations of relative linear polarizations of the exciting and ionizing laser beams are discussed. Received 1st August 2000 and Received in final form 2 May 2001     

Recommended conventions for defining transition moments and intensity factors in diatomic molecular spectra

Two recommendations are made that can eliminate persistent confusion in the study of diatomic spectroscopy by providing uniform and consistent definitions of the electronic transition moments and the rotational line intensity factors. First, it is recommended that the equation for the line strength of a single rotational line be adopted to specify the relationship between the electronic transition moment and the rotational line intensity factor. Second, it is recommended that the electronic transition moment operator for perpendicular transitions be defined by (1/2^1/2)(μ_x ± iμ_y). The adoption of these conventions results in a value of (2S + 1)(2J + 1) for the sum rule of the rotational line intensity factor for Σ^± ↔ Σ^± transitions and a value of 2(2S + 1)(2J + 1) for the sum rule for all other spin-allowed transitions.     

Study of the 2-channel systems using the J-matrix method

ABSTRACT

The partial widths and the branching ratios have been calculated for 2-channel systems, using the diagonalisation of a 2-channel full Hamiltonian and the J-matrix quantities related to the free Hamiltonian, for resonance states with different orbital angular momentum ? (? = 0, 1, 2, 3) and different charge z (z = +1,?0,?? 1) for Noro and Taylor potential. Moreover, the 1- and 2-channel Morse potential have been investigated for the two diatomic molecules H₂ and LiH. The basis used is the Laguerre basis. Two approximate methods have been used to calculate the widths and the ratios associated with a spinless projectile?target system. Many results are reported here for the first time, including the results of ? ≠ 0 and z ≠ 0 in 2-channel Noro and Taylor potential, and the results for the two diatomic molecules. The comparison of our outcome with earlier studies, wherever possible, on energies, branching ratios and partial widths, is discussed.     

Hypervirial treatment of centrifugal distortion of 2Π energy levels

An analytical perturbation has been carried out, using a hypervirial scheme, of the wave equation with Morse potential and additional perturbations involving powers of [1-exp(-aq)]. The centrifugal distortion contributions to rovibrational energies are derived for diatomic molecules and compact formulae are obtained for successive radial derivatives of the spin-orbit function. Numerical applications are described to the X²Π states of several molecules.     

On effective molecular electronic charge densities and vibrational potential energy functions

Empirical relationships connecting equilibrium internuclear distances, harmonic force constants and atomic numbers for diatomic molecules which were presented in a recent communication by Anderson and Parr (Chem. Phys. Lett.10, 293 (1971)) are discussed in detail for 4b-6b and 1a-7b molecules as sample cases. It is shown how to estimate cubic and quartic force constants for these diatomic molecules using these relationships. Methods for estimating stretching force constants in polyatomic and excited state diatomic molecules are presented; sample cases CO₂, CS₂, OCS and the states of CO are treated.     

The hyperfine structure of diatomic molecules: Hund's case (cα)

The hyperfine splitting in diatomic molecules is treated according to an unperturbed model that is denoted Hund's coupling case (c_α). The advantages of this model are: (i) Rapid convergence of the perturbation expansion (spin-orbit interaction is included in the unperturbed Hamiltonian), (ii) hyperfine interactions of the type ΔJ ≠ 0 are automatically included, (iii) simple rotational-independent matrix elements result for the hyperfine Hamiltonian, and (iv) it is rather easy to judge whether the various hyperfine parameters are correlated or not. Numberical diagonalization of a secular matrix of dimension (2S + 1)(2I + 1) (or less for singular levels) yields the hyperfine splittings. The interaction with remote electronic states is included through a Van Vleck transformation. The coupling case (c) matrix elements are readily specialized to coupling case (a), and the present method is applied to the a³Π₁ substate of InH (optical), the X³Σ^? state of ³³SO and ¹⁷O¹⁶O (microwave) and to the X²Π state of ⁷LiO (radio frequency).     

Threshold energy electron impact excitation of carbon dioxide and carbon disulphide

The threshold energy electron impact excitation spectra of CO₂ and CS₂ have been studied using the sulfur hexafluoride scavenger technique. The main results are triplet state excitation and autoionisation of negative ions associated with resonant excited states of the molecules. This confirms previous data concerning diatomic molecules. Furthermore, transitions such as ¹Π_g?X¹Σ_g⁺ and ¹Π_u?X ¹Σ_g⁺ are only weakly induced by low energy electrons, while the corresponding triplet excitations are probably more easily produced. Structures at 5.6, 6.1 and 6.6 eV observed in CS₂ are due to negative ions and/or to ³Π_u, ³Π_g excitation.The autoionisation of CO₂^?(X²Π_u) proceeds also by ejection of a thermal energy electron and leads to highly excited vibrational levels (3–5 eV) of the ground electronic state of CO₂.     

Dynamical regimes and intracavity propagation delay in external cavity semiconductor diode lasers

The open shell molecules with even number of electrons have π ² or \({\pi ^{2}_{g}}\) ground-state electronic configuration. Several homonuclear diatomic molecules like O₂, S₂, B₂ have \({\pi ^{2}_{g}}\) ground state in the \(D_{\infty h}\) point group and heteronuclear diatomic radicals like PH, NH, SO have π ² ground state in the \(C_{\infty v}\) point group. We have computed and presented here the rate coefficient of these open shell molecules (O₂, S₂, B₂) and radicals (PH, NH, SO) from the results of our previous studies using a well-established ab-initio formalism: the R-matrix method. The rate coefficients for elastic and electron-excited processes are studied over a wide electron temperature range.