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The result of an IBFM multilevel calculation with the 2p3/2, 1f5/2 and 2p1/2 single particle orbits is reported for the negative parity states of the odd mass nucleus75As. Comparisons are made with experimental data for energy spectra, transition probabilities, mixing ratios, electric quadrupole and magnetic dipole moments. Also, an IBM-1 calculation is presented for the low-lying states in the even-even74Ge core nucleus.

The level structure of 76Se is discussed within the framework of Interacting Boson Models. The calculated energy levels, transition probabilities, mixing ratios, ${Q_{2_1^ + }}$ and ${g_{2_1^ + }}$ are compared with experimental data. Mixed-symmetry states are investigated in the isotopes 72Se, 74Se, 76Se, 78Se and 80Se. Two mixed symmetry states with spin 1+ and 3+ are proposed for 76Se, and also six other 1+ and 2+ levels in the neighbouring selenium isotopes.

The result of an IBFM multilevel calculation with the 3s 1/2, 2d 3/2, 2d 5/2 and 1g 7/2 single particle orbits are reported for the first time for the positive parity states of the odd mass nucleus159Tb. Comparisons are made with experimental data for energy spectra, transition probabilities, mixing ratios, electric quadrupole and magnetic dipole moments. The agreement with the low-lying spectra suggests an extended comparison up to levels with spin 25/2, thereby testing the predictive power of the model.

The rates of diffusion of both Ga and Cu in CdTe have been measured over the temperature ranges 350–820 and 200–400°C respectively and the results are compared with the self-diffusion of Cd (350–920°C). In the case of the Cd self-diffusion the Arrhenius graph showed two active diffusion mechanisms, one dominating above 500°C and the other below. It suggested that in the temperature range 500–800°C the main defect responsible for diffusion was Cd, with a significant contribution at lower temperatures from the associated defect of the form (CdiVcd)x Below 500°C another mechanism predominated which was possibly due to residual impurities. The results for the diffusions were in close agreement with those obtained by other workers. The Ga diffusions showed a complex behaviour which suggested that two mechanisms were active simultaneously, one independent of Cd partial pressure and the other decreasing with increasing Cd partial pressure. It was concluded that CdTe would be suitable as a diffusion barrier to protect HgxCd1 − xTe devices from Ga contamination from GaAs substrates but would not be efficient at reducing Cu contamination from the substrate in the device.

The diffusion of Ga into bulk-grown, single crystal slices of CdTe was studied in the temperature range 350-811 o C where the diffusion anneals were carried out in sealed silica capsules using three different types of diffusion sources. These were: excess Ga used alone, or with either excess Cd or excess Te added to the Ga. Each of the three sets of conditions resulted in different types of concentration profile. At temperatures above 470 o C, a function composed of the sum of two complementary error functions gave the best fit to the profiles, whereas below this temperature a function composed of the sum of one or more exponentials of the form exp(-ax) gave the best fit.

The authors present the results of an analysis of the positive-parity states of the odd-mass nucleus 125Te within the framework of the interacting boson-fermion model. The predictions of the simple single j-orbit calculation for the neutron hole in the 3s1/2 orbital are compared with those of the multilevel approach taking into account other higher-lying single particle orbits, 2d3/2, 2d5/2 and 1g7/2. The calculated energy spectra, transition probabilities and electromagnetic moments and compared with experimental data.

A radiotracer sectioning technique that can be used successfully for measuring concentration profiles in diffused slices of single-crystal CdTe using anodic oxidation is described. The technique is useful when the penetration of diffusant is

The energy level schemes of152Gd and152Sm have been established on the basis of singlesγ-spectra, andγ- γ coincidence measurements. Ge(Li) detectors were used to study the gamma spectra produced in the EC/β+ and β− decays of152Eu to152Sm and152Gd, respectively. Thirteen new transitions are reported and data from eleven coincidence gates enabled five new levels to be suggested. Relative intensities and logf t values were calculated and spin/parities deduced. Comparisons are made with new predictions of the Interacting Boson Model.

New experimental results from the beta - decay of 182Ta to 182W are reported, based on gamma singles and gamma - gamma coincidence measurements. A new decay scheme for 182W is built up, from which several previously reported transitions and five energy levels are removed while five transitions and two new energy levels are added. Energy levels are supported by an IBM-1 calculation in which the SU(3) Hamiltonian is modified by a small pairing interaction.

The nonlinear directional coupler (NLDC) can be used to achieve a number of all-optical signal processing functions that will be required in future switching and routing systems. Particularly attractive would be such a device operating at diode laser wavelengths with the possibility of integration with other optoelectronic components. Previous work on GaAs-based material has demonstrated nonlinear switching in NLDCs at wavelengths near 1 μm.1,2 In this paper we present results of measurements made on a NLDC fabricated in InP-based material operating close to 1.55 μm, which is to our knowledge the first demonstration of a NLDC suitable for integration at this important wavelength for optical fiber transmission.

The level scheme of56Fe was built up from γ-γ coincidence measurements using Ge(Li) detectors and a Dual Parameter data collection system. The previously suggested γ-transitions [8] of 263.3, 410.9, 485.2, 674.7 and 1,462.3 keV were confirmed and evidence found for a new 655.0 keV γ-transition between the levels at 4,100.32 and 3,445.32 keV. No evidence was found for the transition of 2,657.4 keV and the previously proposed β+-feeding of the level at 3,600.3 keV is ruled out, while the existence of a level at 4,447.5 keV is suggested. The relative intensities and branching ratios of 44 transitions were determined. A calculation of experimentalK-shell internal conversion coefficients α(K) showed large discrepancies from previous studies for the 3,009.6 and 3,451.2 keV transitions, the latter being assigned a different multipolarity. Logft values were calculated and spins and parities of the levels deduced. In particular the assignment of 3+ is verified for the level at 4,297.97 keV.

Spin-correlation parameters A/sub L//sub L/, A/sub S//sub L/, A/sub N//sub L/, A/sub N//sub 0/, A/sub S//sub 0/, A/sub L//sub 0/, and A/sub 0//sub L/ have been measured for the reaction pp..-->..np..pi../sup +/ at 492, 576, 643, 729, and 796 MeV. An isobar analysis determines magnitudes and phases of partial waves up to NN /sup 3/F/sub 3/. For the amplitude NN(/sup 1/D/sub 2/)..-->..N..delta..(/sup 5/S/sub 2/), the phase shows a strong threshold enhancement in the N..delta.. channel, dropping from 44.4/sup 0/ +- 4.4/sup 0/ at 492 MeV to 11.9/sup 0/ +- 1.9/sup 0/ at 796 MeV. Other phases show little activity. Broad dibaryons are conclusively ruled out in /sup 1/D/sub 2/, /sup 3/F/sub 3/, and /sup 3/P/sub 2/ in this energy range

Data on spin correlation parameters ASL, ALL and ANO for pp → π+d are reported at 492, 729 and 796 MeV. The 729 MeV ASL data are important in stabilising the amplitude analysis near that energy.

The energy level schemes of192Os and192Pt have been established on the basis ofγ- γ coincidence studies using a dual parameter data collection system. Ge(Li) detectors were employed to study the gamma spectra produced in the E.C. andβ− decays of192Ir to192Os and192Pt, respectively. Thirteen new transitions and three new levels at 1,146.95, 1,237.35 and 1,913.76 keV are suggested. Relative intensities from singles measurements, branching ratios,α(K) and log ft values were calculated and multipolarities, spins and parities deduced. Comparisons are made with predictions of the Interacting Boson Model calculated on the basis of an O(6) to SU(3) transition.

The energy level scheme of182W has been established from γ — γ coincidence studies following the β decay of182Ta. A Dual Parameter Energy-Time spectrometer used a pair of Ge(Li) detectors and a plastic scintillation detector for data collection. Fifteen new transitions were observed and five new energy levels at 1,460.41, 1,592.98, 1,620.36, 1,712.29, and 1,762.91 keV are suggested. The lifetime of three energy levels at 100.10, 1,289.45 and 1,553.57 keV were measured using the method of delayed coincidences. Relative intensities for the transitions and branching ratios of the energy levels were determined. ExperimentalK shell internal conversion coefficients α(K) and logft values were calculated and multipolarities, spins and parities deduced. Comparisons are made with theoretical predictions from the general collective model, the pairing plus quadrupole model and in particular theSU(3) limit of IBA calculations.

The possible effect of the recently discovered subshell closure at Z=64 is investigated for 160Dy. Energy levels and B(E2) ratios are compared with IBM-1 calculations assuming either a single Z=50-82 shell or subshell closure at Z=64. The latter calculation improves agreement with experiment.

MEASUREMENTS of ozone and some primary pollutants, including oxides of nitrogen and total hydrocarbons, have been in progress at the Central London background site of this laboratory since July 1972. A preliminary note1 discussed the early results from this site; here we present a statistical analysis of the relationship between ozone levels in Central London and some meteorological parameters measured at the London Weather Centre, ∼ 0.4 km from the sampling site. The data were collected during the periods July–September 1972 and April–September in both 1973 and 1974.

Part of the instrumentation for measurement of pollution from motor vehicles is described. The methods are selected for sensitivity and selectivity and will give a continuous record. Calibration is important and selected example procedures are described. The data-handling problem is overcome by inclusion of a 10-channel logger with punched paper tape output.

AMONG the reactions of primary pollutants with one another and with substances naturally present in air, the reactions induced by light are particularly important. The occurrence of such reactions is related to the accumulation of strongly oxidizing species, particularly ozone1, which occurs naturally in the atmosphere to the extent of 20–50 p.p.b. during daylight2,3. Ozone can be detected by smell by sensitive individuals at 100 p.p.b.4, which value is a suitable threshold for an air quality evaluation, having been proposed as an air quality standard in the USA5.

THE isolation of 1,2-benzanthracene and 4′-methyl-1,2-benzanthracene from a crystalline mixture of benzanthracene homologues, obtained from fractions of a Kuwait mineral oil by reaction with maleic anhydride, was described in an earlier communication1. We have now isolated another isomer from the mixture and identified it as 7-methyl-1,2-benzanthracene, and obtained some insight into the composition of the monomethylbenz-anthracene fraction by gas–liquid chromatographic analysis.

Concern that relative phases of /sup 1/D/sub 2/, /sup 3/F/sub 3/, and /sup 3/P/sub 2/ NN..-->..N..delta.. partial waves determined from pp..-->..np..pi../sup +/ data from 492 to 796 MeV might allow resonances (dibaryons) has arisen. This comment is a reaffimation of our conclusion against resonances due to interference with the strong /sup 3/P/sub 1/..-->../sup 3/S/sub 1/ NN..-->..NN..pi../sup +/ (N..pi.. S waves) amplitude because the interaction is strongly repulsive. (AIP)

Two hydrocarbons previously isolated from a Kuwait mineral oil have been identified as 1,3,6,8- and 1,4,5,8-tetramethylanthracene. 1,3,6,7- and 2,3,6,7-Tetramethylanthracene have been isolated from a high-boiling fraction of an Oklahoma oil. Syntheses of 1,3,6- and 1,3,7-trimethyl-, and of 1,3,5,7-, 1,3,6,8-, and 1,4,5,8-tetramethyl-anthracene are described. The 1,3,6-trimethyl- and 1,3,6,8- and 1,4,5,8-tetramethyl compounds are incorrectly described in the literature.The chemical shift of the methyl protons of a methyl-substituted anthracene depends on the position of attachment of the group to the nucleus and may provide a useful aid in the identification of an unknown polymethyl-anthracene.

1-Methylchrysene and 1,2- and 1,7-dimethylchrysene have been isolated from a high-boiling fraction of a Kuwait mineral oil and identified by comparison with authentic specimens. The synthesis of 1,7-dimethylchrysene is described. From a crystalline mixture of methyl homologues of 11-thiabenzo[a]fluorene obtained from the oil, the 4-methyl isomer was isolated, and the presence of the 1- and 10-methyl derivatives was shown by gas chromatography.

A hydrocarbon isolated from a fraction of a Kuwait mineral oil has been identified by synthesis as 1,2,7,8-tetramethylfluorene. A crystalline mixture of methylbenzo[a]fluorenes from an Oklahoma oil is shown by gas chromatography to contain at least six components, four of which have retention times coincident with those of the 1-, 3-, 4-, and 10-methyl isomers. Syntheses of 1-, 3-, and 4-methylbenzo[a]fluorene are described.