Fluorescence studies of CS2 and SO2 at 121.6, 73.6–74.4 and 58.4 nm

The fluorescence spectra of CS₂ and SO₂ have been studied at three incident photon wavelengths of 121.6, 73.6–74.4 and 58.4 nm and relative production cross sections for different product states have been measured. The CS(A ¹Π→X ¹Σ⁺) system between 240 and 290nm has been obtained when CS₂ is photoexcited at 121.6nm whereas CS ₂ ⁺ (B ²Σ _u ⁺ →X ²Π _g ) and CS ₂ ⁺ (A ²Π _u →X ²Π _g ) systems have been produced between 276 and 295 and 437 and 555nm respectively when excited by both the incident photon wavelengths of 73.6–74.4 and 58.4nm. The fluorescence spectra of SO₂ obtained at 121.6 and 73.6–74.4nm include the vibrational bands of SO(A ³Π→X ³Σ⁻) and SO(B ²Π⁻→X ³Σ⁻) systems from 240 to 268 and 268 to 442nm respectively whereas the emission spectrum at 58.4nm, has contributions from the two SO systems and SO⁺(A ²Π→X ²Π) system. In all these emission spectra, the fluorescence bands of different systems have been analyzed and their relative production cross sections have been measured. The results obtained in the present investigations have been compared with a few recent reliable measurements reported in literature.     

Electron-vibrational energy exchange in collisions of Ar atoms in the 3P2 metastable state with N2(X1S g+ ) molecules

Rate constants for electron-vibrational energy exchange Ar(³ P ₂) + N₂(X ¹Σ _g ⁺, ν = 0) → Ar(¹ S ₀) + N₂(C ³Π _u , ν′), where ν′ = 0, 1, 2, were calculated. Calculations were performed taking into account the presence of a resonance in electron scattering by N₂(X ¹Σ _g ⁺). As a result, the interaction of Ar(³ P ₂) with N₂(X ¹Σ _g ⁺, ν = 0) was characterized by attraction and, in the end, intersection of electron-vibrational potential surfaces correlating with Ar(³ P ₂) + N₂(X ¹Σ _g ⁺, ν = 0) and Ar(¹ S ₀) + N₂(C ³Π _u , ν′) at interparticle distances of 2.5–3.5 ?. Exchange interaction at which electron-vibrational transitions in the region of intersection of electron-vibrational transitions in the region of intersection of electron-vibrational potential surfaces accompanied by spin exchange were induced was calculated by the asymptotic method. The rate constants determined at 300–600 K were on the order of 10⁻¹¹−10⁻¹² cm³/s and weakly increased as the temperature grew. Mainly the C ³Π _u , ν′ = 0 state of the N₂ molecule was populated. The calculation results were in satisfactory agreement with the experimental data obtained at 300 K.     

Polar-center phase nuclei in He+-irradiated CuO single crystals

Irradiation of various single-crystal CuO faces [ac,bc,(110)] with 4.6-MeV He⁺ ions has been found to result in reduction of CuO to Cu₂O and Cu on the irradiated and unirradiated sides, lifting of forbiddenness from optical transitions in the [CuO₄]⁷⁻ electron center in the 0.7–0.95-eV energy range, a change in dichroism near the bands corresponding to transitions in the hole centers, [CuO₄]⁵⁻, and electron centers, [CuO₄]⁷⁻, as well as in a resonant increase of absorption at 0.95–1.30 eV with an unusual polarization dependence. The results of He⁺ irradiation of CuO single crystals are discussed in terms of a model of the nucleation of the phase of polar (electron and hole) centers in copper-oxygen systems. Fiz. Tverd. Tela (St. Petersburg) 40, 419–424 (March 1998)     

Rotational measurements on (4–6), (5–7) bands of CN (B2Σ+ − X2Σ+) transition

Rotational analysis of (4–6), (5–7) bands of CN (B ² Σ ⁺ −X ² Σ ⁺) transition extending to highJ and emitted from the chemiluminescent reaction involving pink afterglow of nitrogen is presented.     

Determination of the probability of existence of pair interactions in the formation of M2tX2t?1Superstructures in MXy nonstoichiometric compounds

An analytical method has been proposed for calculating the probabilities P _i ^(2)(s) of existence of X-X, X−□, and □−□ pair interactions in the nonmetal sublattice of M _2tX_2t−1 superstructures formed in strongly nonstoichiometric compounds MX _y (MX _y □_1−y) and M ₂X _y (MX_y/2□_1−y/2) with a high content of structural vacancies □. The main characteristics necessary for the quantitative determination of the probabilities P_i(2)(s) as functions of the composition, degree of long-range order, symmetry, and structure type have been determined for all the known superstructures M _2tX_2t−1.     

T-violation and neutron optics experiments

It is shown that a two-step model of the reaction pd→³HeX (X=η, η′ eω, φ), involving the subprocesses pp) →dπ⁺ and π⁺ n→Xp, can account for the form of the energy dependence of experimental cross sections above the thresholds under the assumption that the singlet part of the pp→dπ⁺ amplitude dominates. The spin-spin asymmetry for the reaction dp→³HeX has been found to be ∼;−1 in the forward-backward approximation. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 1, 3–7 (10 January 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Laser photoacoustic spectroscopy of iodine molecule: Single and two-photon absorption

Photoacoustic spectroscopy of iodine molecule has been studied in gas phase using nitrogen laser-pumped tunable dye laser. The experiment yielded the vibrational spectrum corresponding toX ¹Σ⁺(0 _g ⁺ )→B ³Π(0 _g ⁺ ) transition up to the convergence limit. The photo-acoustic spectrum in the region 17580–18850 cm⁻¹ is presented along with the vibrational analysis. Five of the vibrational bands reported earlier by Venkateswarlu, Kumar and McGlynn have been partially resolved and the structure of one of them has been analyzed and shown to be due to an overlap of (14, 2) and (12, 1) bands. The analysis was based on a comparison with the highly resolved spectrum of Gerstenkorn and Luc. The structure observed in the region 20200–20750 cm⁻¹ which is beyond the convergence limit of the transitionX ¹Σ⁺(0 _g ⁺ )→B ³Π(0 _u ⁺ ) has been analyzed as due to two-photon absorption. Most of the bands could be assigned to two transitions both originating in the ground state and terminating in two different electronic states 1 _g andE(0 _g ⁺ ), atT _e=40821 cm⁻¹ (orT ₀=41355 cm⁻¹) andT _e=41411 cm⁻¹ (orT ₀=41355 cm⁻¹) respectively.     

The emission band system c2 Σ + — x2 Π of NH+

Five red degraded bands belonging to theC ² Σ ⁺ —X ² Π system of NH⁺ were excited in a mild condensed discharge through flowing ammonia and were photographed on a 3.4 meter Ebert grating spectrograph at a dispersion of 2.5 A/mm. The rotational analyses of these bands enabled us to evaluate the vibrational and rotational constants accurately. The rotational energy levels of theΠ ⁺ andΠ ⁻ levels of theν=0 and 1 levels of the ground state,X ² Π, were fitted in James expression using two sets of rotational constants. The perturbations observed in theX ² Π state caused by thea ⁴ Σ ⁻ state were examined in greater detail.     

Associated production of light gravitinos in e+e? and e?γ collisions

Light gravitino productions in association with a neutralino (selectron) in e ⁺ e ⁻ (e ⁻ γ) collisions are restudied in a scenario that the lightest supersymmetric particle is a gravitino and the produced neutralino (selectron) promptly decays into a photon (electron) and a gravitino. We explicitly give the helicity amplitudes for the production processes by using the effective goldstino interaction Lagrangian, and present the cross sections with different collision energies and mass spectra. We also examine selection efficiencies by kinematical cuts and beam polarizations for the signal and background processes, and show that the energy and angular distributions of the photon (electron) can explore the mass of the t-channel exchange particle as well as the mass of the decaying particle at a future e ⁺ e ⁻ (e ⁻ γ) collider.     

On the spin correlations of muons generated in the annihilation process e + e ? → μ+μ?

Using the technique of helicity amplitudes, the electromagnetic process e ⁺ e ⁻ → μ⁺μ⁻ is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ⁺μ⁻) system is analyzed. It is shown that in the case of unpolarized electron and positron the finalmuons are also unpolarized, but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ⁺μ⁻) system are derived. The formula for the angular correlation at the decays of final muons μ⁺ and μ⁻, produced in the process e ⁺ e ⁻ → μ⁺μ⁻, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have the purely quantum character, since one of the incoherence inequalities for the correlation-tensor components is always violated. The additional contribution of the weak interaction of lepton neutral currents through the virtual Z ⁰ boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon spin correlations does not change. The text was submitted by the authors in English.     

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     

Spin correlations of muons in the process of electron-positron pair annihilation e + e ? → μ+μ?

Using the technique of helicity amplitudes, the electromagnetic process e ⁺ e ⁻ → μ⁺μ⁻ is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ⁺μ⁻) system is analyzed. It is shown that in the case of unpolarized electron and positron the final muons are also unpolarized, but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ⁺μ⁻) system are derived. The formula for the angular correlation at the decays of final muons μ⁺ and μ⁻, produced in the process e ⁺ e ⁻ → μ⁺μ⁻, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have the purely quantum character, since one of the incoherence inequalities for the correlation tensor components is always violated. The additional contribution of the weak interaction of lepton neutral currents through the virtual Z ⁰ boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon spin correlations does not change.     

Spectral Properties of Hypoelliptic Operators

 We study hypoelliptic operators with polynomially bounded coefficients that are of the form K=∑ _i=1 ^m X _i ^T X _i +X ₀+f, where the X _j denote first order differential operators, f is a function with at most polynomial growth, and X _i ^T denotes the formal adjoint of X _i in L ². For any ɛ>0 we show that an inequality of the form ||u||_δ,δ≤C(||u||_0,ɛ+||(K+iy)u||_0,0) holds for suitable δ and C which are independent of yR, in weighted Sobolev spaces (the first index is the derivative, and the second the growth). We apply this result to the Fokker-Planck operator for an anharmonic chain of oscillators coupled to two heat baths. Using a method of Hérau and Nier [HN02], we conclude that its spectrum lies in a cusp {x+iy|x≥|y|^τ−c,τ(0,1],cR}. Received: 30 July 2002 / Accepted: 18 October 2002 Published online: 25 February 2003 RID="*" ID="*" Present address: Mathematics Research Centre of the University of Warwick Communicated by A. Kupiainen     

Dislocation spectroscopy of crystals

A new method of studying the energy characteristics of dislocations is proposed, which is based on the investigation of the interaction of moving dislocations with purposefully introduced electronic and hole centers. A study has been made of KCl, NaCl, KBr, LiF, and KI alkali halide crystals containing electronic F and hole V _K and Me ⁺⁺ (Cu⁺⁺, Ag⁺⁺, Tl⁺⁺, In⁺⁺) centers. Investigation of the temperature dependence of the dislocation interaction with the F centers permitted determination of the position of the dislocation-induced electronic band (DEB) in the band diagram of the crystal. In KCl, the DEB is separated by ≈2.2 eV from the conduction-band minimum. It is shown that dislocations transport holes from the centers lying below the dislocation-induced hole band (DHB) (X ⁺, In⁺⁺, Tl⁺⁺, V _K) to those above the DHB (the Cu⁺ and Ag⁺ centers). Such a process is temperature independent. The DHB position in the crystal band diagram has been determined; in KCl it is separated by ≈1.6 eV from the valence-band top. The effective radii of the dislocation interaction with the electronic F and hole X ⁺, V _K, and Tl⁺⁺ centers have been found. Fiz. Tverd. Tela (St. Petersburg) 41, 2139–2146 (December 1999)     

Intensity distribution in theA 2Π –X 2Σ+ system of Yttrium monoxide

The integrated intensities of a few bands in the vibrational structure of the astrophysically significant ‘orange’ system of the molecule yttrium monoxide, have been measured experimentally by the technique of photographic photometry. The effective vibrational temperatures of the source are found to be 2402±180 K and 2901±230 K for the subsystemsA ²Π_3/2−X ² Σ ⁺ andA ²Π_1/2−X ² Σ ⁺ respectively.     

Confrontation of nucleus deformation and multipole mixture parameters in (2+0 n ?2+01) transitions with rotational band structure for K π = 0 2+ and 0 3+

The difference of the energies of levels Δ _n = E _lev(2⁺0 _n ) − E _lev(0⁺0 _n ) at n = 1, 2, and 3 and the multipole-mixture parameter δ for (2⁺0₂−2⁺0₁) and (2⁺0₃−2⁺0₁) transitions are contrasted against the structure of the K ^π = 0₂⁺ and 0₃⁺ rotational bands that was calculated on the basis of the quasiparticle-phonon model. The values of (Δ₂ − Δ₁), (Δ₃ − Δ₁), and (Δ₂ − Δ₃) are found to correlate with the sign of the parameter δ and with the calculated structure of the K ^π = 0₂⁺ and 0₃⁺ bands. Original Russian Text ? A.M. Demidov, L.I. Govor, V.A. Kurkin, I.V. Mikhailov, 2009, published in Yadernaya Fizika, 2009, Vol. 72, No. 2, pp. 236–240.     

Variations of ionic binding energies and the distribution of charge carriers in orthorhombic La2−x Sr x CuO4

The significance of heterovalent, substitutional disorder for the distribution of charge carriers in La_2−x Sr _x CuO₄ has been investigated. Disorder is shown to cause strong variations of binding energies of the ions ranging to some eV for Sr contentsx=0.1. Balancing the energy for a hole transport, Cu³⁺+O²⁻→Cu²⁺+O⁻, and taking binding energy variations into account, the process is realized to become possible without consuming energy for a subset Θ for allx Cu³⁺ in one formula unit of La_2−x Sr _x CuO₄. The functions Θ(x) are presented for hole transports to apex and in-plane oxygens, respectively. The delocalization of charge carriers is interpreted to be caused by valency disorder on metal lattice sites.     

Quasi-elastic neutrino-nucleus reactions

The quasi-elastic contribution of the nuclear inclusive electron scattering model developed in [A. Gil, J. Nieves, and E. Oset: Nucl. Phys. A 627 (1997) 543] is extended to the study of electroweak charged current induced nuclear reactions at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for long-range nuclear (RPA) correlations, final state interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions ¹²C(ν _μ , μ ₋)X and ¹²C(ν _e, e⁻)X near threshold are also given. Presented by M. Valverde at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Collisions of alkali K and Rb atoms in ground state: Modification of interaction potentials

The interaction of alkali K and Rb atoms that reside in the ground state is considered in the range of collision energies E = 10⁻⁴ to 10⁻² au. The singlet (X ¹Σ⁺) and triplet (a ³Σ⁺) interaction potentials available in the literature are analyzed and modified. For the KRb dimer in the range of interatomic distances 15–21a ₀, we chose analytical representations of the singlet and triplet potentials that more accurately describe the interaction of alkali Rb and K atoms in the ground state. Complex cross sections of the spin exchange are calculated for the first time that permit one to calculate the processes of polarization transfer and relaxation times, as well as shifts in the magnetic resonance frequencies caused by K-Rb spin exchange collisions.     

Ab initio calculations of the deformation potentials for intervalley phonon-assisted transitions in АIIIВV crystals with sphalerite structure

Completely self-consistent ab initio calculations of scattering of electrons between the lowest minima of the conduction band by short-wavelength phonons are performed for the first time for a group of А ^III В ^V semiconductor crystals. The structure constants, electron and vibrational spectra, and probabilities of scattering are calculated for the crystals from unified positions within the electronic density functional method. The theory does not involve any phenomenological assumptions on positions of minima in the conduction band, effective carrier masses, interatomic forces, or scattering probabilities. The electron-phonon coupling constants (the deformation potentials) for actual Γ−X, Γ−L, and X−L transitions for scattering between the nonequivalent X−X and L−L valleys in the conduction bands of AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb crystals with sphalerite structure are calculated. Results obtained are compared with theoretical calculations within the phenomenological rigid ion model and with those performed by the selfconsistent frozen phonon method.