Selenium dioxide: Vibrational analysis of the 3130 Å1B2-X̃1A1 absorption system

The B absorption system of the three isotopic species ⁷⁸Se¹⁶O₂, ⁸⁰Se¹⁶O₂, and ⁷⁸Se¹⁸O₂ have been comparatively studied in the vapor phase. The 0_0⁰ band is at 31955.0/31957.4/31963.9 cm^?1, respectively. The main vibrational structure is due to 1_0ⁿ2_0^m progressions, with maximum intensity at n ～ 6. The stronger progressions are those with m = 0, 1, 2, 3. The progressions are severely perturbed. The molecule is bent in both of the combining electronic states. In the ground state for the (80, 16) species, ν₁″(a₁) = 922.6, ν₂″(a₁) = 372 cm^?1. In the electronically excited state, identified as ¹B₂, ν₁′, and ν₂′ have the approximate values 649 and 258 cm^?1, respectively. Evidence is presented in favor of a double-minimum potential function with respect to Q₃′, the band 3_0¹ being observed with appreciable intensity. The height of the potential barrier is about 600 cm^?1.     

Study of the I=2 ππ scattering from the reaction π−d → π−π−psp at 9.0 GeV/c

We have studied the I=2, ππ scattering using the classical Chew-Low extrapolation method. Results are given on the cross sections and the phase shifts δ₀², δ₂² and δ₄² up to 2.2. GeV. δ₀² values are -7.8 ? 3.0° at the K^o mass, -15. ? 1.5° at the ? mass and -29. ? 2.2° of the f^o mass. Above the f^o mass |δ₀²| decreases.     

Laser absorption spectroscopy of the A1Σu+-X1Σg+(v′, v″) bands of Na2

Laser absorption spectra of the band system A¹Σ_u⁺-X¹Σ_g⁺(v′,v″) of Na₂ in the range between 16835 and 16960 cm^?1 are analyzed. The spectra are free of first-order-Doppler broadening at low internal temperature. Rotational and vibrational assignments of 10 bands are reported. Rotational and vibrational levels, especially the (22, 1) band, are found to be perturbed by the b³Π_u state. The band origins and line frequencies calculated from previously reported constants do not reproduce the observed values. The disagreement between the calculated and observed values is discussed. More accurate constants are needed to predict the line locations.     

VUV-UV luminescence of magnetoplumbite: (Sr0.96−xBa0.04)Al12−yMgyO19:Tbx

The title compounds (Sr_0.96−xBa_0.04)Al_12−yMg_yO₁₉:Tb_x (0<x<0.4; 0<y<0.18) are single-phase magnetoplumbite determined by X-ray powder diffraction analysis. The characteristic emission lines of ⁵D₃→⁷F_j (j=2, 3, 4, 5) and ⁵D₄→⁷F_j (j=4, 5, 6) of Tb³⁺ are recorded under the VUV excitation. The intensive luminescence mainly comes from ⁵D₃→⁷F_j transition when the concentration of Tb³⁺ is low. However, when the concentration of Tb³⁺ starts to increase from very low concentration, ⁵D₄→⁷F_j transition is becoming dominant. Three broad excitation bands at 165, 193 and 233 nm have been observed. The band at 165 nm originates from the overlap between the host absorption and the charge transfer of Tb³⁺-O²⁻. The other two broad bands are the first spin-allowed and the spin-forbidden of 4f-5d transition, respectively. The experimental observation of the 4f-5d transition of Tb³⁺ is consistent well with the theoretical expectations.     

Vibrational study of layered ZnPS3 compounds intercalated with [Co(η5 -C5H5)2+] and [Cr(η6 -C6H6)2+] CATIONS

Infrared and Raman spectra (10–3100 cm^?1) of the layered ZnPSs compound and of intercalates with [Co(η⁵ ? C₅H₅)₂⁺] and [Cr(η⁶ ? C₆H₆)₂⁺] cations in the polycrystalline state have been recorded 300–10 K temperature range. A complete assignment of the spectra is proposed in terms of PSs group motions, Zn²⁺ ion translations and [Co(η⁵ ? C₅H₅)₂⁺] or [Cr(η⁶ ? C₆H₆)₂⁺] internal vibrations. New low frequency for the [Co(η⁵-C₅H₅)₂⁺] intercalate at low temperature are assigned to librational and torsional modes of C₅H₅ rings. Moreover, the preresonance Raman spectra of this intercalate show a selective enhancement for the metal-ligand vibrations when the charge transfer band of the cobalticenium is approached. One concludes that guest molecules are intercalated under their cationic form, are weakly interacting with the host lattice and seem to be dynamically disordered at room temperature.     

Photoionization of molecular oxygen in the X3Σg− and a1Δg states

Calculations are carried out, at similar levels of approximation, of the photoionization cross-sections for the ground X³Σ_g^? and metastable a¹Δ_g states of O₂ leading to the X²Π_g state of O₂⁺. Estimates, based upon measurements for the X³Σ_g^? state, are made of the photoionization cross-section of the a¹Δ_g state for transitions populating excited states of O₂⁺.     

Structural study of Pr1−xCaxMnO3 and Y1−xCaxMnO3 perovskites

The structural properties of Prx_1?xCa_xMnO₃ and Y_1?xCa_xMnO₃ perovskite systems were studied by X-ray and magnetic susceptibility measurements. The differences in the structural properties of both systems are attributed to the differences of tolerance factors, i.e. of ionic radii of the ions present and the results are interpreted as being due to simultaneous action of steric effect, orbit-lattice interactions of Mn³⁺ ions and Coulomb interactions among 3d electrons. Their individual contributions depending on the compositions are analyzed. Besides the usual cooperative Jahn-Teller effect existing in PrMnO₃ a new type of transformation was found which is connected, under condition of Mn³⁺ ? Mn⁴⁺ valency migration, with the formation of local Jahn-Teller distortions. It is characterized by the equality of v_hop and v_phon at a critical temperature T_crit; it has been found that T_crit depends only very weakly on the composition. A correpsonding O'→O change in the yttrium system is, however, rather continuous which is explained by a strong influence of the cooperative buckling effect. An analysis of the magnetic data points to the presence of double exchange in the praseodymium system at high temperatures, while at low temperatures this mechanism applies only in the region, where cooperative Jahn-Teller effect exists, i.e. at x0.4.     

Phonon density of states of CdI2 deduced fro,the fine structure of the 3A2g → 1Eg electronic transition of CdI2:Ni2+

The absorption and MCD spectra of the ³A_2g → ¹E_g transition of CdI₂:Ni²⁺ at about 12,500 cm^?1 have been measured. The unusual vibronic fine structure is explained by the coupling of the phonons of the CdI₂ lattice to the electronic states of Ni²⁺. The dispersion curves for the acoustical and optical branches in the Brillouin Zone of CdI₂ are deduced.     

High-resolution Fourier spectrometry of 14N2 infrared emission spectrum: Extensive analysis of the B3Πg-A3Σu+ system

The B³Π_g-A³Σ_u⁺ system of N₂ excited in a microwave discharge was recorded between 3 000 and 18 000 cm^?1 with a high-resolution Fourier spectrometer. There are no observed irregularities in the levels of the A³Σ_u⁺ and B³Π_g states at least for the values of v and J considered here, except the predissociation in the B³Π_g state for v = 12 and J higher than 33. This predissociation will be checked with more complete data in another article. Thirty three bands of the first positive system with 0 ≤ v′ ≤ 12 and 0 ≤ v″ ≤ 8 are analyzed. The molecular parameters of the B³Π_g and A³Σ_u⁺ are obtained by a complete fitting procedure. Derived values of equilibrium constants are deduced; RKR potential energy curves for the two states are constructed, and the Franck-Condon factors calculated for the A-B system.     

Intensity measurements for the (2, 0) γ-band of O2, b1Σ+g−X3Σ-g

Quantitative intensity measurements have been made for the oxygen γ-band at 6280 Å. Intensities for 19 individual rotational lines of the P_P and P_Q branches and the intensity of the combined R_R and R_Q branches are reported. The band intensity, S^v′_v^″, is found to be 1.52±0.07 cm^-1km^-1atm^-1 (STP).     

ESR of Vk centers in CsI

V_k centers (self trapped hole I^?₂) have been obtained in CsI doped with Tl⁺ or Na⁺ by X-irradiation at low temperature and studied by ESR. Spin-Hamiltonian parameters are calculated and compared with those obtained for I^?₂ in the other alkali iodides, as well as the energy of the forbidden transition ²Σ⁺_u→²Π_u and the s and p components of the fundamental state.     

Intensities of the v1-bands of 12CH335Cl and 12CH337Cl near 3 μm

Strengths of individual lines in the v₁ fundamental of methyl chloride have been measured at low pressure and at 296.35 K using a Fourier transform interferometer. The band strengths S_v⁰ obtained by fitting these measurements are 85.8±1.0 and 86.6±1.0 cm^-2 atm^-1 for ¹²CH₃³⁵Cl and ¹²CH₃³⁷Cl, respectively. The Q₃-branch appears to be useful for atmospheric detection of methyl chloride.     

Observation of the c3Πu-X1Σg+ intersystem transition in the absorption spectrum of P2

The observation of the c³Π_u-X¹Σ_g⁺ intersystem transition of P₂ is reported. The 6-0 band of the system was identified on high resolution absorption plates teken on the NRC 10-m vacuum spectrograph at Ottawa. A rotational analysis of the band is given together with that of the adjacent 5-0 band of the C¹Σ_u⁺-X¹Σ_g⁺ system, the upper level of which is involved in a mutual perturbation with the c³Π_u, v = 6 level. The interaction parameters for the perturbation are derived. It is proposed that the appearance of the 6-0 band of the c³Π_u-X¹Σ_g⁺ transition is due to intensity borrowing from the strong, allowed C¹Σ_u⁺-X¹Σ_g⁺ system. Accurate values for the energies of the c³Π_u, b³Π_g, and a³Σ_u⁺ states relative to the ground state are given. The analysis of two other bands, 2-0 and 7-0, of the C¹Σ_u⁺-X¹Σ_g⁺ system whose upper levels likewise interact strongly with the c³Π_u state are also given.     

An X-Y Coriolis perturbation in ν4 of CD3Br

The region 2242–2273 cm^?1 of the ν₄ band in CD₃Br was remeasured at a resolution limit of 0.025 cm^?1. Line assignments were extended up to J = 50 in some subbands. Transitions in the KΔK = ?8 subband were assigned, and the perturbation apparent in this region was attributed to the x-y Coriolis interaction with ν₃ + ν₅^±1 + ν₆^±1. The x-y Coriolis coupling parameter W_xu and the ν₃ + ν₅^±1 + ν₆^±1 band center (in cm^?1) are 0.01960 and 2339.17 for CD₃⁷⁹Br, while the corresponding values for CD₃⁸¹Br are 0.01956 and 2337.95.     

The analyzing power Ay(θ) for the 9Be(p, n)9B reaction from 8 TO 15 MeV

The analyzing power A_y(θ) for the ⁹Be(p, n)⁹B reaction was measured at seven energies between 8.1 to 15.0 MeV for reaction angles between 0° and 100° (c.m.). The A_y(θ) values are predominantly negative and exhibit a smooth variation with energy. The significance of these results in Lane optical- model calculations for the ⁹Be + nucleon system and in comparisons between the observables P^y(θ) and A_y(θ) is indicated.     

ESR and photoacoustic spectra of V2O5−MO2 (M = Se, Te, Ge) glasses

ESR spectra of V₂O₅?MO₂ (M = Ge, Se, Te) glasses are investigated in the range 298–498 K. The spectra at 298 K are characteristic of V⁴⁺ with the 3d¹ electron localized on a single ${}^{51}\text{V}\text{(I =}\text{7}\text{2}$) in the glass network. At higher temperature, the hyperfine structure progressively broadens, leading eventually to a broad, single ESR peak. These results are consistent with thermally-induced electron hopping from V⁴⁺ to V⁵⁺. Photoacoustic spectra of the glass at 298 K are characteristic of V⁴⁺ in a distorted octa environment. A correlation of ESR and PAS data suggests that covalency increased as M is charged from Ge through Te to Se.     

High-resolution infrared study of Coriolis resonances in the ν9 and ν10 bands of allene-d4

The infrared perpendicular bands ν₉ and ν₁₀ in allene-d₄, which are located at 824 and 666 cm^?1, respectively, have been studied at a resolution near to 0.010 cm^?1. The bands were analyzed by taking into account the z-Coriolis resonance between these bands and the (x,y)-Coriolis resonance between ν₁₀ and ν₄(B₁), which is only Raman active. Upper-state parameters and interaction constants are derived from this analysis. Additional Coriolis interactions between ν₉ and ν₃(A₁) as well as between ν₁₀ and 2ν₁₁²(B₁,B₂) are also discussed. Special attention is paid to the study of l-type doublings. Doublets due to q^(?) doubling were resolved both in ν₉ and in ν₁₀. l-type doubling constants including their signs are also obtained.     

Charged particle multiplicity distributions for 32 GeV/c K±p and pp interactions and for 50 GeV/c π±p interactions

Topological cross sections are presented for K⁺p, K^?p and $\text{p}\text{p}$ interations at 32 GeV/c and for π⁺p and π^?p interactions at 50 GeV/c observed in the 4.5 m Mirabelle hydrogen bubble chamber at Serpukhov. Parameters characterizing the behaviour of the multiplicity distributions, namely 〈n_c〉, D and f₂ and the normalized moments are given. The dependence of these parameters on the energy and the nature of the beam particle is discussed. The multiplicity distributions obtained cannot be described by a single function in the KNO variables.     

Magnetic and electrical properties of amorphous Ge1−xCrx thin films grown by low temperature vapor deposition

Amorphous Ge_1−xCr_x thin films are deposited on (1 0 0)Si by using a thermal evaporator. Amorphous phase is obtained when Cr concentration is lower than 30.7 at%. The electrical resistivities are 1.89×10⁻³–0.96×10² Ω cm at 300 K, and decrease with Cr concentration. The Ge_1−xCr_x thin films are p-type. The hole concentrations are 5×10¹⁶–7×10²¹ cm⁻³ at 300 K, and increase with Cr concentration. Magnetizations are 7.60–1.57 emu/cm³ at 5 K in the applied field of 2 T. The magnetizations decrease with Cr concentration and temperature. Magnetization characteristics show that the Ge_1−xCr_x thin films are paramagnetic.     

Room temperature magnetic entropy change and magnetoresistance in La0.70(Ca0.30−xSrx)MnO3:Ag 10% (x=0.0−0.10)

The magnetic and magnetocaloric properties of polycrystalline La_0.70(Ca_0.30−xSr_x)MnO₃:Ag 10% manganite have been investigated. All compositions are crystallized in single phase orthorhombic Pbnm space group. Both, the insulator–metal transition temperature (T^IM) and Curie temperature (T_c) are observed at 298 K for x=0.10 composition. Though both T^IM and T_c are nearly unchanged with Ag addition, the MR is increased. The MR at 300 K is found to be as large as 31% with magnetic field change of 1 T, whereas it reaches up to 49% at magnetic field of 3 T for the La_0.70Ca_0.20Sr_0.10MnO₃:Ag_0.10 sample. The maximum entropy change (ΔS_Mmax) at near its T_c (300.5 K) is 7.6 J kg⁻¹ K⁻¹ upon the magnetic field change of 5 T. The La_0.70Ca_0.20Sr_0.10MnO₃:Ag_0.10 sample having good MR (31%^1 T, 49%^3 T) and reasonable change in magnetic entropy (7.6 J kg⁻¹.K⁻¹, 5 T) at 300 K can be a potential magnetic refrigerant material at ambient temperatures.