Relaxation mechanisms of the Zeeman sublevels of the phosphorescent triplet state of pyrazine at 1·6K

The observed change in the phosphorescence decay of the spin-aligned triplet state of pyrazine at 1·6K upon application of a magnetic field is examined both experimentally and theoretically. Experimentally, the decay curve is resolved into the three decay components of the three triplet sublevels in the field range of 0–6000 G. Both the decay constants and the fraction of total initial intensity of each decay component are determined for each field strength. Theoretically, the observed change in the decay characteristics is assumed to be solely due to the Zeeman mixing of the zero-field levels in the absence of spin-lattice relaxation processes. This has the effect of distributing the radiative strength of the strongly radiative zero-field level among the other two weakly radiative zero field levels. A simple approximate calculation gives excellent and encouraging agreement with experimental quantities in the range of validity of the approximations made (below 1000 G). A rigorous calculation was then performed using the exact solution of the secular equation resulting from the Hamiltonian including the spin-spin and Zeeman interactions. Due to the difficulty in finding a host of known crystal structure in which pyrazine can dissolve substitutionally and uniquely, the comparison between theory and experiment is made using a polycrystalline sample. A special averaging procedure is used in calculating a theoretical decay curve for each magnetic field strength used. The theoretical decay curve is then decomposed into three components employing the same computer programme used for decomposing the experimental decay curve. The agreement between the observed and the more rigorous calculated decay quantities is excellent up to 2000 G, but observed disagreement appears above 3000 G and increases with field strength. The calculated lifetimes above 3000 G are found to be longer than the observed ones. The difference is due to other relaxation mechanisms at these high fields, for example, in spin-lattice relaxation processes between the Zeeman sublevels of the lowest triplet state.     

The contribution of 2N photon absorption in C(γ,2N) reactions for Eγ = 150–400 MeV

The ¹²C(γ,pn) and ¹²C(γ,pp) reactions have been studied using tagged photons of energy E_γ = 150–400 MeV. Recoil momentum distributions are compared to the results of Monte Carlo calculations based on a two-nucleon photon absorption model and two different phase space models. The ¹²C(γ,pn) data at low missing energy are consistent with absorption on 1p² and 1s1p nucleon pairs.     

Researcher,Teacher, Education Researcher: The Evolution of a University Geoscience Instructor

This case study describes a professor's evolution from geoscience researcher to effective teacher to education researcher. The article details his initial beliefs about teaching, looks at the factors that prompted him to seek a different teaching approach, and enumerates the supports and challenges that he had on his journey. Factors essential to this evolution are early career success in discipline research, an institutional climate to reward teaching, mentoring support by colleagues, access to professional development opportunities, and involvement in action research activities. The case study is linked to education literature about teaching and education research and makes recommendations based on the findings of the study.     

Proton spectra from the 6,7Li(γ,p) 5,6He reactions at Eγ = 60 MeV

The ${}^{\mathrm{6,7}}\text{Li}\text{(γ,}\text{p}\text{)}$ reactions have been investigated for E_γ = 60 MeV. Excitation of residual (1p)^?1 and (1s)^?1 hole states is evident from the proton spectra measured at ?_p = 45°. The data are compared with a theoretical calculation which includes short-range correlations.     

A novel synthesis of 1,2-diphosphorylbenzenes

Synthesis of phosphorylchloroacetylenes, diphosphorylacetylenes and the Diels-Alder reactions of the latter to produce $\text{o}$-diphosphorylbenzenes are described.     

Vibrational excitation of molecules in a lattice due to shock induced molecular deformation

A simple formalism is developed to calculate the rate of internal vibrational excitation of a molecule in a lattice due to abrupt deformation of the bonds of the molecule as a result of the application of a shock pulse to the lattice. The excitation rate is calculated as a function of rise time of the pulse and peak pressure for the case of 1,3,5-trinitro, 1,3,5-triazocyclohexane. It is shown that large vibrational excitation rates can be achieved if the rise time of the shock pulse is in the order of the period of vibration of the bond. The possible role of this process in shock induced chemical reactions in solids is considered.     

Determination of boron in geological materials by inductively-coupled plasma emission spectrometry

Determination of boron in international silicate reference materials with an argon plasma is demonstrated. Detection limits are about 5 ppm for rock samples.     

Polarization in inclusive reactions

A formalism for discussing the spin dependence of inclusive reactions is presented. The role of various constraints following from conservation of parity and angular momentum conservation is discussed. Expressions for specific single and double polarization observables are presented. Predictions of the triple-Regge model for these observables are given.     

Amplitude analyses of the reactions π+p → (ϱ0, ω) Δ++ at 7.1 GeV/c

New data are presented, in the form of statistical tensors, for the reactions π⁺p → (?⁰, ω)Δ⁺⁺ at 7.1 GeV/c. Using these data, two types of model-dependent amplitude analyses have been performed. Both analyses, though based on different sets of assumptions, yield results which are in agreement with each other. The structure observed in the magnitudes and phases of the extracted amplitudes is consistent with that expected on the basis of currently accepted phenomenological ideas.