A study of branching ratios of cross sections in the charge symmetric reactions10B(d,p)11B and10B(d,n)11C

High-spin states in¹⁵⁶Er have been populated using the (α, 8n) and (¹⁶O, 4n) reactions. In the ground state band a strong backbending effect was observed atI ^π=12⁺. Four states of a secondK=0 band with spins 9, 11, 13 and 15 were found. This second band depopulates completely into the 8⁺ and 10⁺ members of the ground state band. This is explained by the fact that the upper states of this second band are yrast states and that this band crosses the (gsb)-line atI ?11.     

Optical transitions of Ag− centers in alkali halides

Ag^? centers in alkali halides give rise to a strong absorption band in the 300 nm region (formerly called “B band”). Its resolved triplet structure in CsCl suggests that it corresponds to the C band of the isoelectronic In⁺ center. Two very weak bands are found in several alkali halides in the 400 nm region. These new bands are assigned to the A and B transitions of the In⁺-type centers. This is supported by the doublet structure in the A band, and by the temperature dependence of the oscillator strength of the B band. In KCl∶Ag^? the ratios of the oscillator strengths are found to bef _c /f _A =610 andf _c /f _B =3,400 at low temperatures. The energy parameters of Ag^? centers are computed and compared with those of others ²-type centers. The electron-lattice coupling parameters are estimated from the Jahn-Teller splitting of the C band in CsCl and of the A band in KC1. The temperature dependence of the lifetime of the visible fluorescence suggests that a metastable state is involved in the emission process after a C band excitation.     

The decay of174Ta

Levels in¹⁷⁴Hf excited in the decay of¹⁷⁴Ta have been studied. Measurements of gamma-rays, conversion electrons and gamma-gamma-time coincidences were performed. The ground state band, the beta-vibrational band, the gamma-vibrational band with its head at 1226.81 keV, aK=3⁺ band at 1303.42 keV and aK=2^? octupole band at 1308.67 keV were observed. Several 2⁺ levels withK=0 are excited. The mainβ ⁺-branches proceed through allowed or first-forbidden transitions to the 2⁺ and 4⁺ levels of the ground state band. The character of theI ^π=3⁽⁺⁾ ground state of¹⁷⁴Ta is discussed.     

Wavenumbers,line strengths,and assignments in the Doppler-limited spectrum of formaldehyde from 2700 to 3000 cm−1

The spectrum of H₂CO from 2700 to 3000 cm^?1 has been examined at Doppler-limited resolution using a tunable difference frequency laser spectrometer at Lincoln Laboratory. The wavenumbers and strengths of 4350 absorptions have been determined with an accuracy of 0.001 cm^?1 and 5%, respectively. These data have been incorporated into the analysis of lower-resolution data from Florida State University to assign 72% of the observed absorptions to one of seven bands: ν₃ +ν₄ (a C-type band at 2655 cm^?1), ν₃ + ν₆ (a B-type band at 2719.156 cm^?1), ν₁ (an A-type band at 2782.457 cm^?1), ν₅ (a B-type band at 2843.326 cm^?1), ν₂ + ν₄ (a C-type band at 2905 cm^?1), 2ν₃ (an A-type band at 2999.5 cm^?1) and ν₂ + ν₆ (a B-type band at 3000.066 cm^?1). The band ν₃ + ν₄ has been observed for the first time, and the band center for 2ν₃ has been corrected from a value of 2972 cm^?1 to the value listed above. The effects of strong Fermi and Coriolis resonances on the spectra are discussed.     

High-resolution stimulated Raman gain spectrum of the ν1 band of SF6

We report rotationally resolved stimulated Raman gain spectra of the ν₁ band of SF₆. The fundamental band exhibits a rigid-rotor type spectrum that is readily fit with a band origin of Δα = 774.5445 and a single rotational term Δβ = ?1.10376 × 10^?4 cm^?1. We also observed and analyzed the ν₁ + ν₆ hotband with band origin at 774.1820 cm^?1. With an experimental resolution of 0.0024 cm^?1 there is no evidence for centrifugal distortion or tensor splitting in either band, although the ν₁ + ν₆ band does exhibit first-order Coriolis splitting as expected.     

Exciton spectra and electrical conductivity of epitaxial silicon-doped GaN layers

Optical spectra and electrical conductivity of silicon-doped epitaxial gallium nitride layers with uncompensated donor concentrations N _D — N _A up to 4.8 × 10¹⁹ cm^?3 at T ≈ 5 K have been studied. As follows from the current-voltage characteristics, at a doping level of ～3 × 10¹⁸ cm^?3 an impurity band is formed and an increase of donor concentration by one more order of magnitude leads to the merging of the impurity band with the conduction band. The transformation of exciton reflection spectra suggests that the formation of the impurity band triggers effective exciton screening at low temperatures. In a sample with N _D — N _A = 3.4 × 10¹⁸ cm^?3, luminescence spectra are still produced by radiation of free and bound excitons. In a sample with N _D — N _A = 4.8 × 10¹⁹ cm^?3, Coulomb interaction is already completely suppressed, with the luminescence spectrum consisting of bands deriving from impurity-band-valence band and conduction-band-valence band radiative transitions.     

Investigation of vibrational levels in226Ra by coulomb excitation and by the226Ra(d,pnγ) reaction

Vibrational bands in²²⁶Ra were studied by Coulomb excitation and by the²²⁶Ra(d,pnγ) reaction. The first-excitedK ^π = 0⁺ and 1^? bands with known band heads at 825 and 1049 keV, respectively, were extended up to the 8⁺ and 7^? levels. A new 2⁺ level at 1110 keV and the known 2⁺ level at 1156 keV were observed following Coulomb excitation and interpreted asγ vibration and possible member of a second-exitedK ^π = 0⁺ band, respectively. TheE1 andE2 branching ratios from these vibrational bands to the ground and first-excited 0^? band are explained within the rotational model including band mixings. No evidence was found for a 0⁺ level at 650 keV proposed earlier.     

V centers in single crystal Al2O3

From optical and thermal bleaching experiments it is concluded that the 400 nm absorption band which appears in Al₂O₃ after γ-irradiation is a composite V band. One of its components is attributed to the V^-_OH center which also is responsible for a localized vibrational band at 3316 cm^-11 analogous to the one observed for the V_OH center in MgO. The irradiation also results in electron trapping at Cr³⁺ impurity ions to produce a band at 227 nm. Annealing at 170°C destroys the V^-_OH center by releasing holes which convert the Cr²⁺ to Cr³⁺ with an attendant thermoluminescence.     

Diode laser spectrum and analysis of the 882-cm−1 band of s-tetrazine

A high-resolution diode laser spectrum of the 882-cm^?1 band of s-tetrazine has been obtained. A complete rotational analysis of this band, incorporating quartic and sextic centrifugal distortion coefficients, has been carried out. The rotational constants A, B, and C have been determined with an accuracy better than 10^?5 cm^?1. The analysis has shown the band to be A-type and, on this basis, the vibrational assignment of this band has been revised from ν₁₂ to ν₁₄.     

Hydrogen maser atomic beam resonances

Au^? ions at anionic places are formed in gold doped crystals by a reducing treatment withF centers. The ultraviolet absorption consists of 4 bands, which are namedA, B, C, andD in analogy to the isoelectronic centers of the s² type, like Tl⁺. TheB band oszillator strength strongly increases with temperature in accordance with a phonon allowed transition. The ratio of the dipole strength of theC band to that of theA band as a function of the relative position of theB band is compared with Suganos prediction. Zero phonon lines are found at helium temperatures for theA band in NaCl (2,985 Å), KCl (3,068 Å), and KBr (3,145 Å) and for theC band in KCl (2,329 Å). In KCl the Huang-Rhys factor isg=3.4 for theA band. The vibronic structure comes from the relatively large radius 6s ² state of the negative ion. Uniaxial stress splits the zero phonon line. The results definitely agree with the stress splitting behaviour of a degenerateΓ ₁→Γ ₄ transition. Inversion symmetry of the center is confirmed by the absence of a linear Stark effect.     

Band structures in73Se

Excited states of⁷³Se have been investigated up to spin, 21/2 using techniques of in-beamγ-ray spectroscopy in connection with the⁷⁰Ge(α, n) reaction. Mean lifetimes of 12 levels have been determined applying Doppler-shift andγ-RF-methods. Five different bands have been identified that reflect a variety of different excitation modes. The decoupled 9/2⁺ band is likely to correspond to an oblate deformation while the 5/2⁺ band is interpreted as a strongly coupled prolate band built on the Nilsson configuration [422] 5/2⁺. The 3/2^? band is a strongly coupled band built on the [301] 3/2^} configuration.Nuclear reactions:⁷⁰Ge(α,n),E=14, 16, 18, 19, 20MeV; measuredE _γ,I _γ,σ(E _γ,θ),γγ-coin, linear polarization, DSA,γ(t).⁷⁵Se deduced levels,I, π, τ, δ(E2/M1), B(σλ). Enriched targets, Ge detectors.     

On the coexistence of oblate and prolate deformed bands in83Zr

Deformation parameters of the positive parity yrast band and negative parity bands in⁸³Zr are deduced from lifetimes andE2/M1 mixing ratios. Lifetimes of high spin states have been determined from recoil distance Doppler shift and Doppler shift attenuation measurements using the⁵⁴Fe(³²S,2pnγ) ⁸³Zr reaction. Ten lifetimes and five lifetimes limits were determined. The positive parity band, built on theg _9/2 K=5/2 orbital has an average deformation ¦β ₂¦=0.28(2), and shows a reduction ofE2 transition strengths in the observed backbend region at I^π≈21/2⁺. In contrast, theE2 strengths in the negative parity states show a steady increase up to I^π≈=15/2^?. These states are more strongly deformed than the positive parity states (¦β ₂¦=0.33(3)). TheE2/M1 mixing ratios show that the negative parity band hasK=3/2 and is prolate, and favour oblate deformation for the positive parity yrast band. In theK=1/2^? band theE2 strength of the 7/2^?→3/2^? transition yields a deformation ¦β ₂¦=0.26(5). The band structure is compared with calculations within the Hartree-Fock Bogoliubov cranking model.     

The perpendicular band ν14 of benzene near 10 μm

The perpendicular band of the E_1u vibration ν₁₄ of C₆H₆, with band origin at 1038.2670 cm^?1, was measured on a Bomem high-resolution Fourier transform spectrometer with a 246-cm optical path difference. The spectrum was deconvolved to an effective linewidth of ～0.002 cm^?1. A total of 135 subbands have been assigned in the ν₁₄ band. The band was found to be remarkably free of perturbations by other states. A Hamiltonian matrix of order 2, including merely the rotational l-type resonances between the ν₁₄⁺(J, K) and ν₁₄^?(J, K ? 2) levels, was used for the treatment of the upper states of this band. A set of accurate spectroscopic constants was obtained, which reproduces a total of 3258 measured lines with an over-all standard deviation of 0.0006 cm^?1.     

High spin bands in120Xe

High spin states in¹²⁰Xe were populated in the reaction¹⁰⁶Cd(¹⁸O, 4n) at a bombarding. energy of 90 MeV and the subsequent de- excitation was studied using γ- ray spectroscopic methods. New levels and several. spin and parity. assignments were established. The yrast band was observed up to theK ^π=22⁺state with two band crossins athw _c=0.39MeV and 0.45Mev Negative parity levels and a new positive parity band were also identified.     

Coulomb excitation of the 242m Am isomer

The ^242m Am isomer, a well-known candidate for photodepopulation research, has been studied in this first ever Coulomb excitation of a nearly pure (≈98%) isomer target. Thirty new states, including a new rotational band built on a K ^π = 6^? state, have been identified. Strong K-mixing results in nearly equal populations of the K ^π=5^? and 6^? states. Newly identified states have been assigned to the K ^π=3^? rotational band, the lowest states of which are known to decay into the ground-state band. Implications regarding K-mixing and Coulomb excitation paths to the ground state are discussed.     

Indirekte Band-Band-Stoßrekombination in Germanium

Photoemission from Ge, caused by carrier injection via ap-n-junction was observed at a wavelength about 1 μm at room temperature. The dependence on energy, temperature and carrier density shows, that there appears a high energy tail of a radiative band to band recombination, which cannot be the tail of the usual radiative recombination in Ge. The intensity of the photoemission is proportional ton ² p ². The experimental results are explained as follows: Via indirect band to band Auger-recombination a hole is brought into the split-off band. In this band, the hole reaches thermal equilibrium with the lattice. While it remains in this band, it is able to recombine radiatively with electrons of the conduction band.     

High-resolution infrared spectrum of CH2D2: The ν3 fundamental band at 7 μm

The infrared spectrum of CH₂D₂ has been recorded in the region of 1345 to 1561 cm^?1 with a resolution of 0.030 to 0.026 cm^?1. Most of the observed lines have been assigned to transitions of the ν₃ band of CH₂D₂. However, 114 lines have been identified as transitions of the ν₂ band of H₂¹⁶O whose band origin has been directly determined to be 1594.7472 ± 0.0030 cm^?1. A few weak lines, probably belonging to the ν₅ fundamental of CH₂D₂, remain unassigned. The band center ν = 1435.1326 ± 0.0030 cm^?1 and a set of upper state constants were obtained for the ν₃ band of CH₂D₂. Although a slight perturbation was noticed in the ν₃ band, all wavenumbers have been fitted with a standard deviation of 3.8 × 10^?3 cm^?1.     

An optical study of the stretching absorption band near 3 microns from OH- defects in LiNbO3

A near infrared absorption band (λ = 2.87 μ), identified as the 0–1 stretching vibrational band of OH^- defects in LiNbO₃, has been observed at 6, 77, and 300 K. This band was completely polarized perpendicular to the crystallographic c-axis within experimental error and two peaks, separated by approximately 13 cm^?1, were resolved. Both the structure and optical anisotropy of this band were independent of stoichiometry and sample treatments and may be understood in terms of a simple model where protons are captured by O^2- anions forming OH^- defects whose orientations are determined by neighboring O^2- ions.     

Photoemission studies of single crystals of titanium carbide

The electron distribution in the valence band from single crystals of titanium carbide has been studied by photoelectron spectroscopy with photon energies h?ω = 16.8, 21.2, 40.8 and 1486.6 eV. The most conspicious feature of the electron distribution curves for TiC is a hybridization between the titanium 3d and carbon 2p states at ca. 3–4-eV binding energy, and a single carbon 2s band at ca. 10 eV. By taking into account the strong symmetry and energy dependence of the photoionization crosssections, as well as the surface sensitivity, we have identified strong emission from a carbon 2p band at ? 2.9-eV energy. Our results are compared with several recent energy band structure calculations and other experimental data. Results from pure titanium, which have been used for reference purposes, are also presented.The valence band from single crystals of titanium carbide have been studied by means of photoelectron spectroscopy, with photon energies ranging from 16.8 to 1486.6 eV.By taking into account effects such as the symmetry and energy dependence of the photoionization cross-sections and surface sensitivity, we have found the valence band of titanium carbide to consist of two peaks. The upper part of the valence band at 3–4 eV below the Fermi level consists of a hybridization between Ti 3d and C 2p states. The C 2p states observed in our spectra were mainly excited from a band about 2.9 eV below the Fermi level. The APW^5–9, MAPW¹⁰ and EPM¹¹ band structure calculations predict a flat band of p-character between the symmetry points X′₄ and K₃, most likely responsible for the majority of C 2p excitations observed. The C 2s states, on the other hand, form a single band centered around ?10.4 eV.The results obtained are consistent with several recent energy band structure calculations^{5–11, 13} that predict a combined bonding of covalent, ionic and metallic nature.     

Identification and intensities of the “forbidden” 3ν23 band of 12C16O2

Lines of the 3ν₂³ “forbidden” band of ¹²C¹⁶O₂ have been identified in the 2000-cm^?1 region of a long-path, 0.01-cm^?1 resolution laboratory absorption spectrum. This band has detectable intensity due to Δl = 2 Fermi interactions between the upper level and the nearby ν₁ + ν₂ and 3ν₂¹ levels. Intensities of 18 lines of this band have been measured using a nonlinear least-squares spectral fitting technique. The intensities are enhanced at high J and an expression for the intensity distribution as derived by Toth [Appl. Opt.23, 1825–1834 (1984)] is used for the analysis. In terms of the total sample pressure, the vibrational band intensity is 0.194 ± 0.008 × 10^?30 cm^?1/molecule-cm^?2 at 296 K. The coefficient in the F factor is analogous to the Coriolis coefficient ξ and has been determined to be ?0.0413 ± 0.0015. As expected by theory, its value is very close to that of ξ for the related ν₁ + ν₂ band.