Inelastic scattering and satellite fine structure in the high-resolution uv photoelectron spectrum of CS2

The outer valence region in CS₂ has been studied by high-resolution UV photpelectron Spectroscopy. The spectra reveal detailed vibrational structure in the X$\text{\$}\text{?}$²Π_g, A$\text{\$}\text{?}$²Π_u, B$\text{\$}\text{?}$²Σ⁺_u and C$\text{\$}\text{?}$²Σ⁺_g bands. Some of the fine-structure peaks in the X$\text{,}\text{?}$B$\text{\$}\text{?}$and C$\text{\$}\text{?}$bands are shown to be pressure-dependent. The reason for the pressure dependence is assumed to be inelastic scattering of electrons emitted in the adiabatic transitions. It is established that the two CI satellite bands present in the He(I)-excited spectrum contain vibrational structure.     

Annealing studies on the absorption spectrum of 41K-atoms trapped in an argon matrix

Argon crystals were doped with 0.2 ppm of ⁴¹K through the nuclear reaction ⁴⁰Ar (n, β^-) ⁴¹K. The absorption spectrum from 300 nm to 800 nm was measured as a function of the annealing temperature. Absorption ← 4²s_{$\text{1}\text{2}$} transition of the free atom could be bands corresponding to the 4²p_{$\text{1}\text{2}$}, _{$\text{3}\text{2}$} ← 4²s_{$\text{1}\text{2}$} and 5²p_{$\text{1}\text{2}$}, _{$\text{3}\text{2}$} ← 4²s_{$\text{1}\text{2}$} transition of the free atom could be observed. The absorption bands depend strongly on the annealing temperature. An increase in the annealing temperature results in a blue shift of the absorption bands.     

Intrinsic states,high-spin rotational bands and rotation alignment in 177Os and 179Os

Low-lying intrinsic states and their associated rotational bands have been identified in ¹⁷⁷Os and ¹⁷⁹Os. They are the mixed i_{$\text{13}\text{2}$} neutron states and the $\text{1}\text{2}$^?[521] states in ¹⁷⁷Os and ¹⁷⁹Os, as well as the $\text{5}\text{2}$^?[512] state in ¹⁷⁷Os and the $\text{7}\text{2}$^?[514] state in ¹⁷⁹Os. The $\text{1}\text{2}$^? sta is assumed to be the ground state, the other intrinsic states giving rise to isomers. The in-band decay properties of the $\text{7}\text{2}$^?[514] band, and the i_{$\text{13}\text{2}$} bands show the effect of mixing. In the rotational bands in ¹⁷⁷Os a low frequency backbending anomaly is observed but no anomaly is observed in the i_{$\text{13}\text{2}$}. band. In ¹⁷⁹Os the i_{$\text{13}\text{2}$} band does backbend but at a higher frequency than in the yrast bands of the even neighbours. The systematics of the backbending frequencies, and the effects of blocking, are discussed. The rotation aligned angular momentum is deduced, and a comparison made between the i_{$\text{13}\text{2}$} bands and the s-bands in the even neighbours. The results broadly support the identification of the s-bands with the aligned (i_{$\text{13}\text{2}$})² configuration.     

The systematics of h112 proton alignment in 157, 158, 159Er

Rotational bands have been observed in ^{157, 158, 159}Er to very high spin ($\text{J ～ 41}\text{h}\text{?}$). Upbends are found, due to the alignment of two h_{$\text{11}\text{2}$} protons at $\text{0.40 ?}\text{h}\text{?}\text{ω ? 0.46}\text{MeV}$ in all bands. A systematic shift with neutron number of the band-crossing frequency is observed and is related to a change in quadrupole deformation ?₂.     

Effects of cation order on the energy bands of GaAs-AlAs heterostructures

Pseudopotential band structure calculations of (GaAs)_n ? (A$\text{l}$As)_n with n = 1, 2, 3 and of Ga_0.5A$\text{l}$_0.5As show that the effects of cation order are small due to the weakness of the Ga-A$\text{l}$ potential difference. The energy bands of the n = 1 heterostructure can be obtained by folding those of the alloy except for small energy shifts and splittings which can be handled in perturbation theory. The superlattice energy gap decreases with increasing n, the shrinkage being 4 meV for n = 2 and 10 meV for n = 3.     

The visible and photographic infrared spectrum of osmium oxide

The emission spectrum of OsO has been photographed in the region 405–875 nm where many new bands have been observed. In favorable cases the ${}^{190}\text{OsO}{}^{192}\text{OsO}$ isotopic splittings have been resolved and aid in vibrational assignments. Three visible bands in the region 433–470 nm have been assigned as (1,0), (0,0), and (0,1) of a $\text{ΔΩ}\text{= 0}$ electronic transition. The (0,0) and (0,1) bands have been rotationally analyzed, yielding principal constants (cm^?1) for the visible system of ν₀ = 22 273.3, B′₀ = 0.3657, D′₀ = 2.8 × 10^?7, B″_e = 0.4023, D″_e = 3.2 × 10^?7, $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 780.7}$, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 884.9}$. A band at 825.4 nm has been found to be a $\text{ΔΩ}\text{= +1}$ (0,0) band with the same lower state as in the analyzed visible bands. Constants for the upper state of the ir system are ν₀ = 12 109.7, B′₀ = 0.3845, and D′₀ = 3.1 × 10^?7 cm^?1.     

Dependence on interatomic distance of exchange coupling in rare-earth Al2 compounds

The effect of pressure on the Curie temperature of the heavy rare-earth dialuminides has been measured up to 3.5 kbar. The derivatives dT_c/d_p are 0.00(4), 0.09, 0.21, 0.39, 0.60 and 0.71 K/kbar respectively for TmAl₂ ErAl₂, HoAl₂, DyAl₂, TbAl₂ and GdAl₂ thus indicating a clear positive correlation between dT_c/dp and the de Gennes factor G. The results are discussed in terms of the RKKY model. However, the phenomenological parameter D/d, where D is the nearest-neighbour R-R distance and d the diameter of the 4f orbital, is used to reflect the non-δ-function character of the sf-coupling parameter Г. The experimental values of Г²D² and T_p/G are found to decrease linearly with increasing D/d. This is in keeping with the RKKY proportionality of $\text{T}{}_{\mathrm{c}}\text{?T}{}_{\mathrm{p}}$ to Γ²E^?1_FG. For GdAl₂, TbAl₂ and DyAl₂ the quantity $\text{?}\text{(}\text{d}\text{T}{}_{\mathrm{c}}\text{d}\text{p}\text{)}\text{k}{}_{\mathrm{l}}\text{(}\text{D}\text{d}\text{)}\text{G}$ coincides within the error limits with the slope of the T_p/G vs D/d plot.     

The 341-nm band system of pyridine N-oxide: Assignment of the out-of-plane fundamentals

Analysis of the 341-nm bands of pyridine N-oxide vapor has been extended to the out-of-plane modes of the molecule in the $\text{X}\text{?}{}^1\text{A}{}_1$ and $\text{A}\text{?}{}^1\text{B}{}_2$ states. Data for the ground state are obtained primarily from infrared and Raman measurements; using this information, the excited-state out-of-plane manifold is then built up by the assignment of overtone, sequence, and cross-sequence bands observed in the electronic absorption spectrum. These assignments lead to a complete set of a₂ and b₁ fundamental frequencies in the $\text{A}\text{?}$ and $\text{X}\text{?}$ states, though some questions cannot be fully resolved, and the uniqueness of the assignments is briefly discussed.     

The 404.5-nm system of the ReO molecule

Observations on the emission spectrum of ReO in the region 375–870 nm are reported. Five bands of a $\text{ΔΩ}\text{= 0}$ system with (0, 0) band at 404.5 nm have been rotationally analyzed and the principal results for ¹⁸⁷ReO are (in cm^?1) ν₀ = 24 709.90, B′_e = 0.3819, B″_e = 0.4252, ω′_e = 874.8₂, and $\text{Δ}\text{G″(}\text{1}\text{2}\text{) = 979.1}{}_2$. Data on the minor isotopic species ¹⁸⁵ReO are also reported. It is suggested that broad rotational profiles found in bands near 842 nm may be due to nuclear hyperfine structure.     

Antiproton-proton total elastic cross sections in the T and U regions (0.69−2.43 GeV/c)

Antiproton-proton total elastic cross sections at 21 incident momenta in the range 0.69 to 2.43 GeV/c have been deduced by combining p?p elastic differential cross sections over a c.m. angular range $\text{?0.95 ?}\text{cos}\text{θ}{}^1\text{? 0.93}$ with forward elastic cross sections derived from recent real-part measurements and p?p total cross sections. Two bumps are observed, at $\text{M}{}_1\text{? 2.155}$ and $\text{M}{}_2\text{? 2.345}\text{GeV}\text{/c}{}^2$, having widths of Г₁ ～ 0.135 and $\text{Г}{}_2\text{～ 0.135}\text{GeV}\text{/c}{}^2$. Corresponding structures in other p?p reaction channels are discussed.     

Dynamic viscosity of macromolecular liquids for a superposition of static and oscillating velocity gradients

Two coupled, inhomogeneous relaxation equations for the friction pressure tensor and the alignment tensor are derived within the framework of irreversible thermodynamics. These equations are solved for a specific geometry, viz. flow between flat plates, and for a velocity gradient of the form $\text{Γ}{}_0\text{+ Γ}{}_1\text{cos Ωt}$ with small Γ₁. From the resulting relation between the (time-dependent) friction pressure tensor and the velocity gradient, the dynamic viscosity and the normal pressure can be inferred. The frequency dependence of the relevant viscosity coefficients is discussed. If Г₀, the magnitude of the static part of the velocity gradient is large enough, a type of resonance behavior is found with the resonance frequency $\text{Ω}{}_{\mathrm{res}}\text{≈(1 + ξ)}{}^{-1}\text{Γ}{}_0$ where ξ is the ratio between the relation times of the friction pressure tensor and of the alignment tensor.     

Rotational analysis of the NO2 6125-Å region

In the NO₂ 6125-Å region 135 transitions belonging to four bands have been assigned using laser-induced fluorescence. On the whole, the rotational structure of the four vibronic bands is well characterized by near-prolate symmetric top relations. The 6125 and 6126-Å bands perturb each other, the former having predominantly the character of the $\text{A}\text{?}{}^2\text{B}{}_2$ state, the latter the $\text{X}\text{?}{}^2\text{A}{}_1$ state; this parent-daughter relationship is recognized to occur else-where in the NO₂ visible spectrum.     

The 370-nm electronic spectrum of tropolone: Evidence from single vibronic level fluorescence spectra regarding the assignment of some vibrational fundamentals in the X̃ and à states

Single vibronic level fluorescence (SVLF) spectra of tropolone from vibronic levels in the $\text{A}\text{?}{}^1\text{B}{}_2$ electronic state, in combination with recently reported supersonic jet spectra, have enabled the assigning of many absorption bands in the region of 0₀⁰ which had previously been impossible. Some of the complexity in these bands has been shown to be due to a large Duschinsky effect involving the two lowest b₁ vibrations, ν₂₅ and ν₂₆. It has been shown that these vibrations have wavenumbers of 176 and 110 cm^?1, respectively, in the $\text{X}\text{?}$ state, and 172 and 39 cm^?1 in the $\text{A}\text{?}$ state. This last value shows how unresistent the molecule is in the $\text{A}\text{?}$ state to out-of-plane bending in the region of the five-membered ring. Other aspects of the vibrational complexity are due to the effect of ν′₂₆ in increasing the barrier to tunnelling of the hydrogen-bonding proton in the $\text{A}\text{?}$ state contrasting with very little effect of ν″₂₆ in the $\text{X}\text{?}$ state.     

Angle resolved photoemission studies of the band structures of semiconductors: PbI2

Angle resolved photoemission data is presented for single crystals of the layered semiconductor PbI₂. The geometric form of the valence electron energy bands has been mapped using a simple approximation and the possible electronic origins of these bands are discussed. Such band dispersion effects in angle resolved measurements are contrasted with HeII excited data for the localised $\text{Pb}\text{5}\text{d}\text{5}\text{2}$ core level component, where “flat” band behaviour and only weak residual final state scattering effects may be discerned. Finally we comment on the role of the incoming photon in such experiments.     

Study of the precipitation behavior of NaCl:Pb and KCl:Pb by optical spectroscopy2

The aggregation and precipitation behavior of lead in NaCl and KCl crystals has been systematically investigated by absorption and luminescence spectroscopy. For NaCl, absorption bands at 265 and 285 nm have been identified which correspond to intermediate stages in the formation of a double band (262–266 nm) associated with PbCl₂ precipitates. The kinetics of growth during ageing as well as the thermal annihilation behavior have been obtained for all bands. The emission spectra for excitation at those absorption bands have also been determined. For KCl, absorption bands at 265 and 280 nm develop during ageing at 160 and 200°C and their growth-rate is markedly enhanced by plastic straining. Their emission spectra involve a main band at $\text{\$}\text{?}$550 nm. In contrast to NaCl, no stage has been found where those absorption bands feed into a final band, which could be associated with PbCl₂ precipitates.     

Rotational analyses and vibrational assignments of the 463- and 474-nm bands of NO2

The excitation spectrum of NO₂ was investigated in the blue region by using a Nd:YAG laser-pumped dye laser. The 463- and 474-nm bands of the ²B₂-²A₁ system were identified and analyzed using the simplification that occurs if the excitation spectrum is monitored at particular wavelengths. Band origins and rotational constants were obtained. Vibrational assignments have been given to these bands by comparing the Franck-Condon Factors calculated for the ²B₂-²A₁ system with the fluorescence intensities of bands going to different vibrational levels of the ground state. The vibrational assignments and molecular constants obtained in this work are (v′₁, v′₂, v′₃) = (3, 11, 0)ν₀(K′ = 0) = 21584.1, $\text{B}\text{= 0.405}$, and $\text{∥}\text{?}\text{′∥ = 0.05}\text{cm}{}^{\mathrm{?1}}$ for the 463-nm band; and (v′₁, v′₂, v′₃) = (2, 12, 0), ν₀(K′ = 1) = 21104.9, $\text{B}\text{= 0.408}$, and $\text{∥}\text{?}\text{′∥ = 0.03}\text{cm}{}^{\mathrm{?1}}$ for the 474-nm band.     

Line-shape of the vibrational bands of the CN- UV emission spectra in alkali halide-cyanide mixed crystals

Measurements of the line-width of the vi$\text{b}$rational bands associated to the a³Π→X¹Σ⁺ electronic transition of the CN ion in alkali halide-cyanide mixed crystals at 2K–250K have been performed. It is obtained that the a³Π→X¹Σ⁺ electronic transition is coupled to a dominant mode of 110 cm^-1 with strength 1.2 in KCN_0.01C?_0.99. From the line-shape of the vibrational bands in all crystals at 4.2K it is suggested that this mode can be ident$\text{i}$fied with a breathing mode of the neighbouring alkali ions.     

The valence band of some light rare-earth metals studied by photoemission spectroscopy

The valence bands of La, Ce, Pr, and Nd have been studied by ultraviolet photoelectron spectroscopy (UPS) (He II, hv=40.8 eV) and compared to results from X-ray photoelectron spectroscopy (XPS)(Mg Kα_{1, 2}). The energy positions of the $\text{4?}$ levels are in good agreement with earlier XPS results and calculations based on estimates from optical and thermodynamic data. The widths of the sd bands and the $\text{4?}$ levels and the relative emission intensities are discussed.     

A study of the electronic structure of Fe3C,Fe3Al and Fe3Si by x-ray photoelectron spectroscopy

The core levels and valence bands of Fe₃C, Fe₃Al, Fe₃Si and their pure components at temperatures ranging from 20 to 1000° have been investigated. Shifts in Fe 2p$\text{3}\text{2}$, C 1s, Si 2p and Al 2p confirm the migration of electrons from iron to carbon and from aluminium and silicon to iron. A study of the valence bands of these compounds shows that their electronic structure is determined, in the first approximation, by the type of the second component atoms.     

Landau-Placzek ratio of KBr single crystals—I

The Mandel'shtam-Brillouin and Gross scattering was measured for a series of purified KBr crystals. The ratio $\text{I}{}_{\mathrm{G}}\text{2I}{}_{\mathrm{MB}}$, which for a pure, perfect crystal would be the Landau-Placzek ratio, was found to vary with the type of reactive gas treatment used in the final purification. With these crystals both the longitudinal and mixed mode bands were observed with θ and φ equal to 90°. The ratio $\text{I}{}_{\mathrm{L}}\text{I}{}_{\mathrm{M}}$ was in agreement with calculated intensity ratios and the Δμ for these bands gave C₁₁ + C₁₂ = 41.6 GPa and C₄₄ = 5.18 GPa.