Amino wagging and inversion in hydrazines: RR branch of the antisymmetric wagging band of NH2NH2

Infrared absorption spectrum of undeuterated hydrazine in the gaseous state has been observed with a resolving power better than 0.06 cm^?1 in the 1024 ～ 961 cm^?1 region, where the ^RR- and ^RQ-branch lines of the antisymmetric wagging band (v_a = 1 ← 0) appear. It has been found that every line belonging to the ^RR branch as well as every ^RQ peak of the band splits into four components, a, b, c, and d. This is explained by considering that the v_a = 0 state splits into A_I, E, and B₂ substates and the v_a = 1 state into B₁, E, and A₂ substates, because of the four equivalent potential minima (D₄) of the hydrazine molecule which are reached by inversions of the two amino groups. From the observed wave numbers of the ^RR lines, effective values of the rotational constants of the B₁, E, and A₂ sublevels of the v_a = 1 state were obtained. On the basis of these values and the ones for the A₁, E, and B₂ sublevels of the ground vibrational state, obtained from a previous microwave study, a discussion of the antisymmetric wagging-inversion coordinate is given.     

Quantizing a classically ergodic system: Sinai's billiard and the KKR method

Sinai's “billiards on a torus,” i.e., free motion of a particle in a plane amongst reflecting discs of radius R centred on points of the unit square lattice, is a classically ergodic system with two freedoms, parametrized by R. Quantal energy levels E_n are given by the vanishing of the Korringa-Kohn-Rostoker (KKR) determinant of solid state theory. This gives a rapid computational scheme for computing E_n as functions of R. Except for the integrable case R = 0, no degeneracies are found, illustrating the theorem that two parameters, not one, are required to make levels cross in a generic system. The same theorem leads to the prediction that the probability distribution of the spacings S of neighbouring levels is $\text{O}$(S) as S → 0, in good agreement with computation. The KKR determinant is transformed analytically to give the level density d(E) semiclassically (i.e., as ? → 0) as the sum of a steady contribution $\text{d}\text{?}\text{(E)}$ and an oscillatory contribution d_osc(E). $\text{d}\text{?}$ is $\text{O}$(?^?2) and is given by the Weyl “area” formula plus “edge,” “corner” and “curvature” corrections, in excellent agreement with computation. d_osc is given by a sum over classical closed orbits (all unstable). Nonisolated closed orbits (not hitting discs) contribute terms with $\text{O}$$\text{(?}{}^{\mathrm{<mtext>?3</mtext><mtext>2</mtext><mtext>)</mtext>}}$ to d_osc, while isolated closed orbits (bouncing between discs) contribute terms with $\text{O}$(?^?1) to d_osc. The isolated orbits are vastly more numerous than the nonisolated orbits and their contributions cannot be neglected. As a means of calculating the individual E_n (rather than the smoothed spectrum), the KKR method is much more efficient than the classical path sum.     

Elastic scattering of 56 MeV polarized deuterons on 4He

The differential cross section and the vector and tensor analyzing powers A_y, A_xx, A_yy and A_xz were measured for the d-⁴He elastic scattering at 56 MeV. The measurement of A_xz was performed using a deuteron beam polarized in the horizontal plane. An optical-model analysis of the experimental data was carried out. The magnitude of the tensor analyzing powers could not be reproduced without the tensor potential. By including the T_R type tensor potential, the optical-model calculations give a reasonable reproduction of the experimental data at θ_c.m. < 120°. The obtained T_R tensor potential was much stronger than that predicted by the folding model. The strength of the real T_R potential was roughly in accordance with that obtained from the optical-model analysis of d-⁴He elastic scattering at 20.2 MeV.     

On directly measuring relative Fermi energies of noble metals and their alloys

We present the first evidence of direct measurement of relative Fermi energies in alloys and between pure metals. From applying the “atomic” concept of core hole final state screening, the Auger energy shift of noble metal A equals E_F^A?E_F(x). High resolution Auger shifts in P_1?x^tCu_x,Au_xCu_1?x and Au_xAg_1?x demonstrate experimental verification of this simple relation. We find E_F^CuE_F^Au ? ? 0.2 eV, and E_F^Pt ? E_F^Cu and E_F^Ag ? E_F^Au.     

An investigation of range distribution parameters of implanted 19F ions in Au,Ag and Cu noble metals

Depth profiles of fluorine implanted in gold, silver and copper metal have been accurately measured using the ¹⁹F(p,αγ)¹⁶O resonance nuclear reaction at E_R = 872.1 keV. A proper deconvolution calculation method was used to extract the depth profile of fluorine from the experimental excitation yield curves. The range parameters, R_p, ΔR_p, and SK obtained in this work were compared with the theoretical calculations. The comparison shows that for all materials studied here the experimental R_p values are in good agreement with the results obtained by the TRIM96 code, while the experimental range stragglings, ΔR_p, are systematically larger than the TRIM simulation results.     

A new space-time model for hadron-nucleus collisons at high energies

A new space-time model for hadron-nucleus collisions is proposed, where particles at the instant of creation are not only immature but their maturity rate is enhanced in the presence of other hadronic matter, as in a nucleus. With only one free parameter, the model can explain dn_A^p/dν, dn_A^π/dν, R_A^p(E_L), and the A-dependences of σ_in^pA and σ_in^πA.     

An analytical model of the heat of chemisorption: A perturbation LCAO MO approach

An analytical LCAO MO perturbation model has been developed for treating the heat of chemisorption Q of an adsorbate A monolayer on a transition metal M film. The model combines parameters of the metal band (the Fermi level E_F, band width W = W^occ + W^vac, the d occupancy N_d, density of states n(?), etc.) with those of the local A-M interactions (the adorbital energy ?_A, off-diagonal matrix elements β_AM, etc.). The major cases of A's having lone pair, singly occupied, and vacant adorbitals have been considered, and the analytical expressions for Q as well as some numerical estimations are presented. The relative values of Q seem to be crucially dependent on the ratio β/(?_A ? E_F). The Q vs. N_d plots for the donor and radical A's are rather flat, typically Q decreasing monotonically as N_d increases, but for the acceptor A's the plots are very parameter dependent and show a variety of trends. The results obtained agree with straightforward computations and (scarce) experimental data.     

Anomalous phonon intensities in the Raman spectrum of disordered CsMg1−xCoxCl3

The five Raman-active $\text{k}\text{= 0}$ phonons have been measured at low temperatures and for a range of x in the disordered lattice CsMg_1-xCo_xCl₃. While the E_2g^a, E_2g^b, E_2g^c and A_1g modes at 55.0, 132.0, 189.0 and 255.0 cm^?1 for x = 0 exhibit normal one-mode behaviour, the intensity of the E_1g phonon at 127.5 cm^?1 has a most unusual concentration dependence which requires a new theory.     

Laser excited Raman spectra of Gr. VI semiconducting compounds

Raman spectra of hexagonal layer compounds MoS₂, MoSe₂ and MoTe₂ were excited by a HeNe laser (6328Å). All the Raman active long-wave-length phonon frequencies were determined. These are A_1g, E¹_2g, E_1g and E²_g. The frequencies decrease as we pass from sulphur to tellurium and the quasiacoustical mode E²_2g has the lowest frequency. A comparison of the results with infrared spectra shows that the i.r. active mode for E ⊥ C is degenerate with one of the Raman active modes in the basal plane for all the compounds.     

Large solutions for harmonic maps in two dimensions

We seek critical points of the functionalE(u)= \(\mathop \smallint \limits_\Omega\) |βu|², where Ω is the unit disk in ?² andu:Ω→S ² satisfies the boundary conditionu=γ on ?Ω. We prove that if γ is not a constant, thenE has a local minimum which is different from the absolute minimum. We discuss in more details the case where γ(x, y)=(R _x,R _y, \(\sqrt {1 - R^2 }\) ) andR<1.     

Secondary electron emission yield behaviour of polymers

The secondary electron emission yields of highly-insulating, thin polymer foils have been measured for incident primary beam energies, 50 ? E_p ? 2500 eV. The results follow closely a ‘universal’ reduced yield curve determined by the energy loss law, dE_p/dx = -A/E_p^n-1, where n = 2 and A is a constant proportional to the density of the solid, as predicted by the elementary theory of Lye and Dekker (1957). This behaviour remains true up to high primary beam energies and, as such, is unique to these low density solids.     

Analysis of the 2ν3 band of 12CD3F at 5.06 μm recorded under high resolution

The 2ν₃(A₁) band of ¹²CD₃F near 5.06 μm has been recorded with a resolution of 20–24 × 10^?3 cm^?1. The value of the parameter (α^B ? α^A) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν₀ = 1977.178(3) cm^?1, B″ = 0.68216(9) cm^?1, D″_J = 1.10(30) × 10^?6 cm^?1, α^B = (B″ ? B′) = 3.086(7) × 10^?3 cm^?1, and β^J = (D″_J ? D′_J) = ?3.24(11) × 10^?7 cm^?1. A value of α^A = (A″ ? A′) = 2.90(5) × 10^?3 cm^?1 has been obtained through band contour simulations of the R(J) and P(J) multiplets.     

The 14N quadrupole coupling constants and barrier to internal rotation of ethylcyanide-d5

The microwave spectrum of ethylcyanide-d₅ has been recorded from 18.0 to 40.0 GHz. Both a-type and b-type transitions were observed and assigned. Also, the R-branch assignments have been made for three excited states of the internal torsional mode and two excited states of the CN inplane bending mode as well as an excited vibrational state involving both of these motions. The barrier to internal rotation was determined to be 3.00 ± 0.15 kcal/mole from the E, A splittings of the third excited state. The quadrupole coupling constants of the¹⁴N nucleus were found to have values of ?3.213, 1.168, and 2.045 MHz for χ_aa, χ_bb, and χ_cc, respectively. These results are compared to those previously obtained on the corresponding hydrogen compound.     

Effect of the second order spin orbit and spin-spin interactions on the E (G) level of Mn in ZnS

An interpretation of the structure of the ⁶A₁ → {₁A₁, ⁴E} zero phonon and phonon assisted transitions is given. Covalency effects show that the ⁶A₁ → ⁴A₁ and ⁶A₁ → ⁴E transitions are well separated; consequently none of the experimentally observed lines can be due to the ⁶A₁ → ⁴A₁ transition. The fine structure for the ⁴E level is interpreted in terms of the spin-spin and spin-orbit interactions. The results obtained are consistent with experiments.     

Second- and third-order elastic moduli of Co I

Elastic moduli of Co with A ₁-type structure are calculated using models in which the total energy is presented in the form of the energy of clusters consisting of pairs, triplets, and quadruplets of identical atoms. The irreducible energies of the clusters are assumed to contain two terms: E ∝ ?τ^?6, corresponding to the mutual attraction of the particles, and E ∝ ?τ^?6, corresponding to their mutual repulsion. Here, τ stands for the half-edge of an elementary cell. All 27 types of models expected in accordance with symmetry theory are analyzed. Of these, the 13 that yielded elastic modulus values satisfying the structural stability criteria are selected. The potentials of the selected models are used to predict the rigidity moduli of Co films with an A2-type structure.     

Ab initio study of PN electronic states – a qualitative interpretation of the perturbation and predissociation effects on observed transitions

Valence and high electronic states of PN have been calculated with accurate quantum chemistry methods. The variety of theoretical methods used includes complete active space self-consistent field, multireference configuration interaction and the newly developed explicitly correlated coupled cluster methods. The large correlation-consistent atomic orbitals basis sets AVQZ, AV5Z and AV(5+d)Z are used for the potential energy curves calculations in the bonding and long-range regions. The spectroscopic constants (R_e, B_e, ω_e, ω_ex_e, α_e, D_e, T_e) and the vibrational levels of the bound valence states (X¹Σ⁺, A¹Π, a³Σ⁺, d ³Δ, e³Σ^?, C¹Σ^?, b³Π, D ¹Δ and E¹Σ⁺ and some higher bound states) are determined and compared with experimental findings when available. Significant spin–orbit interactions between triplet states and A¹Π and E¹Σ⁺ excited states are found near the crossing points of the potential energy curves and could explain predissociation phenomena and the perturbations of the vibrational levels experimentally observed for PN in their A¹Π and E¹Σ⁺ states.     

Luminescence spectra and crystal structure of high-temperature superconductors

A study is reported of the effect of temperature (4.2 K≤T≤150 K), the content of weakly bonded oxygen [6.1≤(7?δ)≤6.9], illumination [E _exc=3.4 eV, (Φt)_max～1.5 ×10²⁰ photon cm^?2, and substitution (Cu → Ag, Cr, Fe, Mn) on the luminescence spectra of the high-T _c superconductor YBa₂Cu₃O_7?δ. Only two bands with E _lum～2.4 and ～2.8 eV were observed in the luminescence spectra in all these cases. A clearly pronounced correlation between the electronic and structural changes in YBa₂Cu₃O_7?δ, caused by the influence of temperature, illumination, doping with oxygen or metal ions, and the spectral parameters (peak position E _lum, width Δλ _lum, and intensity I _lum of the luminescence bands), has been established. It is shown that luminescence spectra of HTSCs can be employed as a fairly reliable optical probe to study the electronic processes occurring in these substances, in particular, the electron (hole) transfer between the CuO₂ plane and the CuO_1?δ chain plane serving as a charge reservoir.     

Emission and laser-excitation spectra of rotationally cooled methylcyanodiacetylene cation (A˜2EāX˜2 E) and photoelectron—photon

The A?²EāX?² E band system of rotationally cooled methylcyanodiacetylene cation has been studied by emission and excitation spectroscopies. Spectra were obtained by electron-impact ionisation of a seeded helium supersonic free jet and by Penning ionisation followed by laser excitation. These data enable the vibrational frequencies of most of the A₁ fundamentals to be inferred for the X?²E (to within ±2 cm^?1) andX?²E (to within ±4 cm?1) states. The fluorescence quantum yields and lifetimes of the cation prepared in selected levels of theA?²E andB?²A₁, excited states have been determined by photoelectron—photon coincidence measurements and yield a quantitative insight into the radiationless-decay pathways.     

Rotational excitation of HD by collisions with He

The information theoretic surprisal analysis is employed to characterise the recent quantal close-coupling computations of rotational excitation rates by Green. The analysis is based on comparing the actual rates to the priors k⁰ which depend only on the temperature and the reduced “energy defect” ΔE_R/kT. The surprisal representation of the computed rates as k=k⁰ x exp (-I₀ - θ_R6ΔE_R6/kT is accurate throughout the temperature range considered by Green and is found to reduce in the low and high temperature limits to functional forms previously employed to characterise the rotational energy transfer rates in H₂.     

The pair distributions and the osmotic coefficient in anomalous electrolytes up to concentrations c≈ 1 mol/1

The osmotic coefficient of anomalous electrolytes up to concentrations c ≈ 1 mol/l is explained by the pair distributions $\text{n(r) =}\text{exp}\text{[-β(}\text{V}{}_{\mathrm{c}}\text{(r) + V(}{}^{\mathrm{hs}}\text{)(r) + V}{}_1\text{(r))]}$. Here $\text{V}$_c(r) is a screened Coulomb potential, V(^hs)(r) a hard sphere potential and V₁(r) = ?A/r⁶ a short range attractive potential. For the contact distances R₊₊, R_?? and R_+? of the hard sphere potentials between ions with the same sign of their charges (++,??) and ions of opposite charges (+?) the relations R₊₊ = R_?? = R and R_+? = q₁R with 0 < q₁ < 1 are assumed. In contrast to a previous paper the parameter q₁ takes a fixed value q₁ ≈ 0,8. The constant A is determined by the fraction q₂ defined by A/R⁶ = q₂(Z²e²/DR) where the positive integer Z is the charge number of the ions and D the dielectric constant of the solvent. The numerical calculation of the osmotic coefficient of 1-1-valent hydrous electrolytes in the range of temperature 273 K ? T ? 293 K shows that the anomalous electrolytes are described by fractions q₂ in the range 0,25 ? q₂ ? 0,5 if the contact distances R are in the range $\text{3}\text{A}\text{?}\text{? R ? 7}\text{A}\text{?}$.