Photoluminescence and luminescence excitation spectra in ZnSiP2

Summary Measurements of photoluminescence and luminescence excitation spectra of ZnSiP₂ have been performed at 4.2K and two results were obtained. One is the observation of a new sharp emission line at 1.980 eV, due to the bound exciton associated with the pseudodirect gap. The other is the observation of another new series of absorption lines in the luminescence excitation spectrum of an emission line, at 1.984 eV, in addition to those reported previously. These results indicate that in ZnSiP₂ radiative transitions occur at both the indirect and the pseudodirect gaps. Paper presented at the ?V International Conference on Ternary and Multinary Compound?, held in Cagliari, September 14–16, 1982.     

Far-infrared spectra of alkali naphthalene ion pairs in solution

The far-infrared spectrum of an ethereal solution of the naphthalene radical anion prepared by reduction with an alkali metal shows an absorption band which is considered to be due to a vibration of an ion pair. The corresponding force constant was calculated for each ion pair from the observed frequency. The obtained values are of reasonable magnitude.     

Nonequilibrium thermodynamics in field theory: Transport coefficients

Transport coefficients are expressed by real time correlation functions of energy-momentum tensor in the linear response approximation. We establish field theoretical method to compute them in perturbation theory, which is demonstrated in λ?⁴ theory.     

s-channel discontinuities of reggeon diagrams with planar vertices

The mutual relations between s-channel discontinuities of reggeon diagrams with planar triple-Regge vertices are discussed. It is shown that, in general, contributions coming from different cuttings are not simply related to each other as certain vertices acquire non-trivial phase factors depending on the nature of the cutting. For diagrams with only triple-Regge vertices this phase may be related to the triple-Regge phase. The complete four-reggeon vertices are not known in general. An approximation is considered which amounts to preserving only the absorptive part of triple- or four-reggeon amplitudes in certain parts of the diagrams. This approximation turns out to be equivalent to a simple absorbed multiperipheral model. The problem of exchange degeneracy breaking within the dual unitarisation Scheme is briefly discussed as an example.     

Binding states of Ga and Sn on W and Mo: Structures,evaporation field and its temperature dependence

Binding states of deposited Ga and Sn on the W and Mo substrates were studied by measuring the evaporation fields of the deposited metal atoms at various temperatures. Ga and Sn form two layers: an overlayer and an underneath pseudomorphic layer which directly contacts the substrate surface. The evaporation fieds of the overlayer Ga and Sn atoms were found to be the same on various crystal planes and significantly lower than that of the pseudomorphic Ga and Sn atoms, indicating that the binding between the overlayer atoms and the pseudomorphic atoms is much weaker than that between the pseudomorphic atoms and the substrate W and Mo atoms. The finding that the evaporation field of the pseudomorphic atoms on W is very close to that on Mo while the evaporation field of W is significantly higher than that of Mo was unexpected. Another interesting finding is that the field emission current from the (011) plane is not noticeably affected by the coverage of the mono-atomic Ga layer arranged in the superstructure while the current from other crystal planes covered by the pseudomorphic layer having the same atomic arrangement with the substrate surface is minimized. Furthermore, it has been found that the evaporation field of the Ga overlayer is lower than that of Sn, while the Ga pseudomorph is more stable than Sn pseudomorph on W surface at temperatures below about 100 K. The temperature dependence of the evaporation field was also examined and compared with existing models.     

Jet calculus: A simple algorithm for resolving QCD jets

It is argued that, in the leading logarithm approximation (LLA) of asymptotically free quantum chromodynamics (QCD), a simple algorithm (jet calculus) can be justified for computing a large number of quantities related to the longitudinal and transverse structure of quark and gluon jets.We formulate the rules of jet calculus in two variables, x and y which are related to longitudinal (energy) and transverse momentum respectively. Throughout the paper, quark and gluon jets are contrasted. After reviewing what has been done on longitudinal spectra, we turn to the transverse structure of jets down to relative transverse momenta of the order of a few GeV (independently of the total energy). The relation of our work to that of Dokshitzer, D'Yakonov and Troyan is elucidated. We also study jets generated by (almost) real photons and compare both with standard “final” parton jets.We also discuss calorimeter measured quantities, compare our results with those of other authors and propose a new and easy way for measuring QCD-predictable anomalous dimensions.We finally give a Lagrangian formulation of jet calculus, as a non-local theory in 1 + 1 dimensions to be solved in the tree approximation.     

Asymptotic expansions for the distributions of functions of a correlation matrix

This paper deals with asymptotic expansions for the non-null distributions of certain test statistics concerning a correlation matrix in a multivariate normal distribution. For this purpose an asymptotic expansion is given for the distribution of a function of the sample correlation matrix. As special cases of the resulting expansion, asymptotic expansions for the distributions of the sample correlation coefficient, Fisher's z-transformation and arcsine transformation are also given.     

Syntheses and properties of emissive iridium(III) complexes with tridentate benzimidazole derivatives

A series of novel emissive Ir(III) complexes having the coordination environments of [Ir(N--N--N)2]3+, [Ir(N--N--N)(N--N)Cl]2+, and [Ir(N--N--N)(N--C--N)]2+ with 2,6-bis(1-methyl-benzimidazol-2-yl)pyridine (L1, N--N--N), 1,3-bis(1-methyl-benzimidazol-2-yl)benzene (L2H, N--C--N), 4'-(4-methylphenyl)-2,2':6',2' '-terpyridine (ttpy, N--N--N), and 2,2'-bipyridine (bpy, N--N) have been synthesized and their photophysical and electrochemical properties studied. The Ir(III) complexes exhibited phosphorescent emissions in the 500-600 nm region, with lifetimes ranging from approximately 1-10 micros at 295 K. Analysis of the 0-0 energies and the redox potentials indicated that the lowest excited state of [Ir(L1)(L2)]2+ possessed the highest contribution of 3MLCT (MLCT = metal-to-ligand charge transfer) among the Ir(III) complexes, reflecting the sigma-donating ability of the tridentate ligand, ttpy < L1 < L2. The emission quantum yields (phi) of the Ir(III) complexes ranged from 0.037 to 0.19, and the highest phi value (0.19) was obtained for [Ir(L1)(bpy)Cl]2+. Radiative rate constants (k(r)) were 1.2 x 10(4) s(-1) for [Ir(ttpy)2]3+, 3.7 x 10(4) s(-1) for [Ir(L1)(bpy)Cl]2+, 3.8 x 10(4) s(-1) for [Ir(ttpy)(bpy)Cl]2+, 3.9 x 10(4) s(-1) for [Ir(L1)2]3+, and 6.6 x 10(4) s(-1) for [Ir(L1)(L2)]2+. The highest radiative rate for [Ir(L1)(L2)]2+ with the highest contribution of 3MLCT could be explained in terms of the singlet-triplet mixing induced by spin-orbit coupling of 5d electrons in the MLCT electronic configurations.