Valence band photoemission spectroscopy of a ternary layered semiconductor: ZnIn2S4

UV photoemission spectroscopy (UPS) experiments have been carried out on the layer compound ZnIn₂S₄ employing several different photon energies in the range $\text{h}\text{?}{}_{\mathrm{\omega }}\text{= 9.5?21.2}\text{eV}$. The energy distribution curves (EDC's) exhibit four valence band density of states structures besides the Zn 3d peak. These five peaks appear 0.90 eV, 1.6 eV, 4.3 eV, 5.8 eV and 8.7 eV respectively below the top of the valence band, E_v. The atomic orbital character of the shallowest peak A appears different from that of the three deeper valence band peaks B, C and D and this is discussed in terms of the more or less pronounced ionic character of the intralayer chemical bonds. These results demonstrate that an overall understanding of the electronic states in complex structures can be achieved by an approach based on photoemission experiments and chemical bonding considerations which has been widely used in the past to study simple binary layer compounds.     

Breakdown of the one electron approximation for 4p core electron energy loss spectra in the rare earths

At high incident electron energies the 4p core electron energy loss features of clean La, Ce and Gd strongly resemble the corresponding XPS spectrum with evidence of strong 4p^-1 ? 4d^-2?f giant Coster-Kronig resonance in the “4p_{$\text{1}\text{2}$}” spectrum. The absence of charge transfer screening peaks in the $\text{4p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ loss of the oxides is attributed to localised 4p → 5d¹ excitation. As the primary energy approaches threshold, a satellite on the low energy side of the $\text{4p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ losses of La and Ce grows in intensity, due to excitations of multiples through non-dipole transitions.     

Relativistic and correlation effects in the anisotropy of near-threshold Kr 3d and Xe 4d photoionization

Angular distributions of the spin–orbit split components and their branching ratios have been studied experimentally and theoretically for the 3d photoelectrons of Kr and 4d photoelectrons of Xe. The focus was on the electron dynamics near the ionization threshold of each spin–orbit split component and its behaviour as a function of Z   in passing from Kr to Xe. The experimental spectra were measured with high photon and electron energy resolutions with photon energies at about 3–12 eV above the 3d_3/2$3{\text{d}}_{3/2}$ and 3d_5/2$3{\text{d}}_{5/2}$ thresholds for Kr and at about 5–12 eV above the Xe 4d_3/2$4{\text{d}}_{3/2}$ and 4d_5/2$4{\text{d}}_{5/2}$ thresholds. Experimental results for the angular distribution parameters have been compared with theoretical values obtained with relativistic Dirac–Fock method and results from independent particle approximation with a modified Hartree potential [A. Derevianko, W. Johnson, K. Cheng, Atom. Data Nucl. Data Tables 73 (1999) 153]. The branching ratios were compared with theoretical predictions from Dirac–Fock and relativistic random-phase approximation [K. Cheng, W. Johnson, Phys. Rev. A 28 (1983) 2820].     

Proprietes optiques et structure electronique de MnAu2

The optical spectrum of the helical antiferromagnetic compound MnAu₂(t_N = 90°C) has been measured, using a scanning ellipsometric method, in UHV, between 0.47 and 5.7 eV, at temperatures ranging from 88 to 700 K. Below 0.6 eV the experimental data can be fitted to a Drude-like intraband model. The maximum of the interband absorption occurs at 5.1 eV, while the onset of interband absorption may be placed at 0?.4eV as is suggested by the rapid rise of $\text{ε}{}_2\text{(ω)}\text{λ}$. below 0.5 eV. In the absence of theoretical work, the analysis of the optical spectrum leads to a preliminary rough model of the electronic structure; the proposed local density of d states is represented. The 5.1eV peak is attributed to d → E_F transitions (parabolic edge at 2.7 eV similar to Au), originating in the lower part of the band, associated mainly with Au sites. To account for the moment $\text{(}\text{3.6μ}{}_{\mathrm{S}}\text{at Mn}\text{)}$, the upper d band (mainly Mn sites) is split: the d↑ band is below E_F (interband edge at 0.4eV), while the d↓ band contains 1.4 electrons. ESCA measurements tend to confirm this model. An important unusual fact is the sharp anomaly of /~ε(ω) in the infrared, around T_N; attempts to correlate this with magnetic (s-d) interactions have been initiated.     

Anomalous two-electron auger resonance in thorium near the 5d(O5) photothreshold

The photoexcited $\text{O}{}_5\text{P}{}_3\text{V (5d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{6p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{valence}\text{)}$ Auger emission line for thorium metal shows an anomalous increase in kinetic energy of ～ 1 eV as the photon energy hv is increased through the atomic-like 5d → 5f resonant excitation at hv_r = 89 eV. Possible mechanisms for this anomalous behavior are discussed, and it is suggested that it can be interpreted as a two-electron resonance involving the O₅P₃V Auger excitation and a shake-up satellite of the $\text{6p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ core level excitation.     

The differential cross section and polarization quantities in the 4He(d,p)n4He and 2H(α, n)p4He reactions

The differential cross section and the polarization quantities (T₁₁, T₂₀, T₂₁, T₂₂, P_γ') in the deuteron breakup reaction by an α-particle are calculated in the framework of the recently developed three-body model. All values are discussed under the incomplete kinematical condition. All polarization quantities are caused by the difference of the potential between $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ waves of the N-α interaction. Results of the calculation are compared with the available measurement of (i) the differential cross section and the deuteron vector analysing power in the ⁴He($\text{d}$, p)n⁴He reaction and (ii) the differential cross section and neutron polarization in the ²H(α, $\text{n}$)p⁴He reaction. The agreement with experiment is very satisfactory in each case. Among the tensor analysing powers of the deuteron the absolute value of T₂₀ is very large. Observables at the FSI peak corresponding to ⁵He_g.s. are discussed systematically in the energy region of 5.4–20 MeV of the incident deuteron in the ⁴He(d, p)n⁴He reaction. Although the differential cross section is not sensitive to the energy of the three-body resonance, the polarization quantities T₁₁, T₂₀, P_γ' are quite sensitive to it.     

The lowest singlet and triplet excited states of pyrazine

The phosphoresence, fluorescence and absorption spectra of pyrazine-h₄ and -d₄ have been obtained at 4°K in a benzene matrix. For comparison, those of the isotopically mixed crystal pyrazine-h₄ in d₄ were also taken. All these spectra show extremely sharp and well-resolved lines and reveal detailed vibronic structure.The coincidence of origins of absorption and emission shows that the lowest singlet state is an allowed transition, properly designated as ${}^1\text{B}{}_{\mathrm{3u}}\text{←}{}^1\text{A}{}_{\mathrm{1g}}$. The forbidden component ¹B_2g, predicted by both “exciton” and MO theories to be below the allowed component, must lie higher. Its exact location still remains uncertain.The phosphorescence spectrum, when compared with the singlet-triplet excitation spectrum, indicates that the lowest triplet state is also symmetry allowed, showing a strong 0-0 band and the coincidence of origins of absorption and emission. In accordance with previous work, the triplet state is designated as ³B_3u.The vibronic structure of the phosphorescence spectrum is very complicated. The first work on the analysis of this spectrum concluded that a simple progression of ν_6a exists. Under the high resolution attainable in the present experiments, the supposed ν_6a progression proves to have a composite structure, starting from the second member of the progression. Not only is the ν_9a hydrogen-bending mode present as shown by the appearance of the CD bending mode in the d₄ spectrum, but a band assigned as 2ν_6b was also identified. The latter's anomalous intensity in the phosphorescence spectrum is interpreted as due to the Fermi resonance with 2ν_6a and ν_9a bands. To help resolve the present controversy over the origin of the phosphoresence spectrum observed in crystalline pyrazine, detailed vibrational analyses of the emission spectra were made. The fluorescence spectrum has essentially the same vibronic structure as the phosphorescence spectrum.     

Infrared and laser Raman gas spectra of GeD4

The ν₂(e) and ν₃(f₂) Raman spectra and the 2ν₃ infrared spectrum of gaseous GeD₄ have been observed and analyzed. The new data have been combined with those of the ν₃(f₂) infrared band to derive an improved set of rovibrational constants. The analysis yields B₀ = 1.3544 ± 0.0010 cm^?1 and $\text{r}{}_0\text{= 1.5223 ± 0.0006}\text{A}\text{?}$.     

Study of the 91Zr(d, 3He)90Y reaction

The ⁹¹Zr(d, ³He) reaction was studied at a deuteron energy of 28 MeV. Angular distributions were measured from 13° to 47°; l_p values were extracted for the prominent lines of ⁹⁰Y. The l_p values and transition strengths were determined by DWBA analysis. The angular distributions for the $\text{(π}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ doublet (g.s. and 0.20 MeV state) exhibit the characteristic l = 1 shape. States at 1.42, 1.57, 1.64 and 1.81 MeV were also populated strongly in the (d, ³He) reaction; the 1.42, 1.57 and 1.81 MeV levels contain l= 1 transition strength and are most likely members of the $\text{(π}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ multiplet. The 2.03 MeV state has a characteristic l = 3 angular distribution and is suggested to be the only member of the $\text{(π}\text{f}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ sextet to be unambiguously observed in this study, most probably the 5^? or 4^? member. The members of the $\text{(π}\text{g}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)(ν}\text{d}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}$ sextet were populated weakly (less than 100 μb/sr) in this reaction.     

Dynamics of the infinite-range ising spin glass

The Glauber dynamics of an Ising spin glass with infinite-range interactions and additional static field, h, is investigated near the freezing temperature, T_f. We obtain critical slowing down at and below the de Almeida-Thouless instability line, h_c(T), to order (1?T/T_f)³ with algebraic decay of the spin correlations ～t^?ν, where $\text{ν=}\text{1}\text{2}$ at T_f and $\text{ν≤}\text{1}\text{2}$ for T<T_f.     

Measurement of the νμ and νμ nucleon charged-current total cross sections,and the ratio of νμ neutron to νμ proton charged-current total cross sections

The total ν_μ and $\text{ν}{}_{\mathrm{\mu }}$ nucleon charged-current cross sections have been measured in BEBC filled with deuterium and exposed to the wide-band neutrino and antineutrino beams at the CERN-SPS. Assuming a linear energy dependence for the cross sections, σ = aE(?_ν, we obtained the coefficients , where the quoted error is mainly systematic. The ratio of the cross sections is $\text{σ}{}_{\mathrm{<mtext>\nu </mtext><mtext>N</mtext>}}\text{/σ}{}_{\mathrm{<mtext>\nu </mtext><mtext>N</mtext>}}\text{= 0.53 ± 0.03}$.We also determined the ratio of the charged-current cross section for neutrino interactions on neutrons and protons R = σ_νn/σ_νp = 2.10 ± 0.08 (statistical) ±0.22 (sysetmatic). The dependence of R on the variables x, y and E_ν is discussed.     

Study of the 4f-levels in rare earths by appearance potential spectroscopy

The yttrium M_4.5-level Auger electron appearance potential spectrum (AEAPS) in the 150–190 eV energy range is presented. AEAPS is a surface sensitive technique that measures the differential secondary electron yield as a function of incident electron energy. The spectral features of AEAPS are determined by the width of the empty conduction band and the degree of localization of the conduction band wave functions. Yttrium (Y) is considered to be one of the rare earth metals with an absence of a 4f state. In lanthanum (La), which has an identical valence electron configuration-to Y, the 4f levels are localized. Comparison of the 3d-level spectrum of Y with that of La shows that though the main peaks remain the same, additional fine structures appear in the spectrum of La. The existence of these structures is correlated with the presence of empty localized 4f levels in La.     

Study of the reactions 118Sn(d,t) and98Mo(d,t): (I). Spectroscopy of 117Sn and 97Mo

The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.0 MeV for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to six states of ¹¹⁷Sn (E_x = 0.0, 0.16, 0.31, 0.71, 1.02 and 1.18 MeV), for ${}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to eight states of ⁹⁷Mo (E_x = 0.0, 0.68, 0.72, 0.89, 1.12, 1.28, 2.39 and 2.52 MeV), and for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{d}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{d}\text{)}$. Deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the $\text{(}\text{d}\text{,}\text{t}\text{)}$ results. Comparison of the measurements and DWBA predictions for σ(θ) and for iT₁₁(θ) allows unambiguous determination of tl_n and j_n for all ¹¹⁸Sn(d, t) and most ⁹⁸Mo(d, t) transitions. Differences in the triton energy relative to the Coulomb barrier cause marked qualitative differences in the measured cross sections and analyzing powers between ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions of the same l_n and j_n.     

Multiplicity distributions and double-scattering effects in π−d interactions at 360 GeV/c

Double-scattering effects are studied in π^?d interactions at 360 GeV/c. The partial cross sections $\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(π}{}^{\mathrm{?}}\text{d}\text{), σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{p}\text{”)}\text{and}\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{n}\text{”)}$ are presented. The double-scattering probability per πd collision is found to be $\text{? = 0.15 ± 0.02}$. We have extracted the partial cross section X_N of the double-scattering plus interference contributions, and find that X_N obeys KNO scaling. The data are compared with various theoretical predictions.     

A theoretical model for the interacting upper states of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands in methane

The effective vibration-rotation Hamiltonians complete to fourth order in the Amat-Nielsen scheme for the upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands in methane are reviewed, and the major vibration-rotation interactions (H₃₀, $\text{H}\text{?}{}_{40}$, $\text{H}\text{?}{}_{21}$, $\text{H}{}_{31}$, $\text{H}\text{?}{}_{22}$) connecting the different vibrational states are discussed. Explicit matrix elements in a basis of harmonic oscillator-symmetric rotor basis functions are given for the purely vibrational terms and for the vibration-rotation interactions. Expressions for spectral intensities of infrared and Raman spectra are presented, and the selection rules and transition moment matrix elements are stated. A computer program is described which, incorporating all these features, can be used for prediction of infrared and Raman spectra and for determination of molecular constants from observed spectra by a least-squares routine. As an example the program is applied to the 2ν₄ isotropic Raman spectrum of ¹²CH₄, leading to a very good agreement between the experimental and calculated spectra.     

The CC stretching band ν6 of allene-d4

The infrared spectrum of C₃D₄ was measured in the region of the paralled band of the CC stretching vibration ν₆ centered at ν₀ = 1920.2332 cm^?1 on a high-resolution Fourier transform spectrometer and deconvolved to a linewidth of $\text{～}\text{1}\text{2}$ of the Doppler width (～0.0023 cm^?1). The high resolution reveals the presence of strong perturbations in the K = 4 and K = 8 to 12 levels of the ν₆ upper state. For a quantitative treatment of the observed transitions, a Hamiltonian matrix including six different perturbing states was constructed and used to refine the 6 spectroscopic constants of the ν₆ state and 20 of the constants for the perturbing states. Measurement of the hot band ν₆ + ν₁₁ ? ν₁₁ whose band center is at 1916.200 cm^?1 yielded the anharmonic constant x_6,11 = ?4.033 cm^?1.     

The ν2 + ν4 band of 12CF4

From a high-resolution diode laser spectrum of cooled ¹²CF₄, line assignments in ν₂ + ν₄ at 1066.4 cm^?1 have been made for tetrahedral subspecies to J = 20, and in many cases to higher J. Spectroscopic constants have been obtained from a least-squares fit of the Hamiltonian, and the relative intensities of the assigned lines have been calculated. The ground- and excited-state rotational constants, Coriolis constant, and splitting of the F₁ and F₂ vibrational substates have the values a.The CF bond length in the ground vibrational state is thus $\text{r}{}_0\text{= 1.31752 ± 0.00007}\text{A}\text{?}$. The analysis of a combination band such as this provides a method of obtaining ground-state spectroscopic constants of spherical-top molecules directly from the infrared spectrum, without the necessity of measuring weak “forbidden” transitions. The assignments allow accurate predictions of the frequencies emitted by the CO₂-pumped CF₄ laser.     

Infrared and laser Raman gas spectra of SiH4 and SiD4

The ν₂(e) and ν₃(f₂) Raman spectra have been examined. For ²⁸SiH₄ the ν₂(e) and ν₄(f₂) infrared bands are partly analyzed and compared with a computed band-contour; the ν₁ + ν₃ combination infrared band has been presented. For ²⁸SiH₄ the 2ν₃ overtone infrared band has been observed and analyzed. The new data are combined with those of the ν₃(f₂) infrared bands to derive an improved set of rovibrational constants of ²⁸SiH₄ and ²⁸SiD₄. The analyses yield $\text{r}{}_0\text{= 1.4806 ± 0.0008}\text{A}\text{?}$ for ²⁸SiH₄ and $\text{r}{}_0\text{= 1.4784 ± 0.0006}\text{A}\text{?}$ for ²⁸SiD₄ in agreement with the Laurie-Herschbach theorem.     

Vibration-rotation spectrum of formaldehyde: CH stretching fundamentals ν1 and ν5

The infrared vibration-rotation spectrum of formaldehyde vapor has been measured in the region from 2600 to 3400 cm^?1 with resolution from 0.04 to 0.07 cm^?1. An extensive rotational analysis of the ν₁ and ν₅ bands has confirmed and superseded the previous band-contour analysis of a medium-resolution spectrum. A large number of subbranches of both the ν₁ and ν₅ bands are perturbed by the combination bands ν₃ + ν₆, ν₂ + ν₄, and ν₂ + ν₆, whereas the Coriolis interaction between ν₁ and ν₅ is weak. The following effective rotational constants (in cm^?1) are obtained:

$\text{ν}{}_1\text{= 2782.49(1), A}{}_1\text{= 9.250(5), B}{}_1\text{= 1.2968(6), C}{}_1\text{= 1.1321(2)}$

,

$\text{ν}{}_0\text{= 2843.35(2), A}{}_0\text{= 9.224(2), B}{}_0\text{= 1.2936(2), C}{}_0\text{= 1.1303(1)}$

, where the number given in parentheses is three times the standard error in the last digit.