Behaviour of single-particle states and their eigenvalues near zero energy

For a state in a single-particle potential we derive simple expressions that the eigenvalue behavior and normalization integral properties near threshold. For the square-well, the various parameters in these expressions can be derived analytically. For the more realistic Saxon-Woods well-shape, we have made numerical calculations for s- and p-states and obtained values of these parameters and give rules for their evaluation. We show that those parameters determining the negative energy eigenvalues are also involved in determining the positive energy behavior, and the normalization properties. These studies have direct relevance to recent theories of some types of (d, p) and (n, γ) reactions which critically involve threshold behavior.     

Temperature program optimization by computer simulation for the capillary GC analysis of fatty acid methyl esters on biscyanopropyl siloxane phases

The selectivity of capillary columns coated with biscyanopropyl siloxane stationary phases for the separation of fatty acid methyl esters has been optimized by means of computer-assisted column temperature optimization software. Temperature programming rates yielding the highest resolution in the shortest analysis time were selected for split, splitless, and on-column injection operated in the constant pressure and pressure programmed modes.     

CBE growth of GaAs/GaAlAs HBTs using the new DEAlH-NMe3 precursor and all-gaseous dopants

This paper describes the first reported use of diethylaluminium hydride-trimethylamine adduct (DEAlH-NMe₃) for the growth of GaAs/GaAlAs power heterojunction bipolar transistors (HBTs) by chemical beam epitaxy (CBE). This precursor possesses a significantly higher vapour pressure than the more conventionally used triethylaluminium (TEA), and leads to much less stringent requirements for bubbler and gas-line heating, and also much-improved GaAs/GaAlAs heterojunction definition when no carrier gas is employed. The use of all-gaseous n- and p-type dopants offers significant technological advantages in CBE, and the current paper also provides the first report of the use of hydrogen sulphide for n-type doping of CBE-grown GaAlAs HBT emitter regions. In conclusion, DC and RF data obtained from the heterojunction bipolar transistors fabricated to date are described. A DC gain of 40 has already been measured and encouraging early data obtained from RF-probed devices are also presented.     

Amplitude correlations in nuclear resonance spectroscopy

Both magnitudes and relative signs of inelastic decay amplitudes have been measured for proton resonances in the compound nuclei ⁴⁵Su, ⁴⁷V, ⁴⁹V, ⁵¹Mn, ⁵⁵Co, and ⁵⁷Co. Resonances with orbital angular momenta 1,2 and 3 and five different values of J^π were studied. For l = 1 and l = 2 resonances, sample sizes are sufficient to perform statistical analyses: distributions of the reduced widths, distributions of the products of reduced width amplitudes, and both amplitude and widt correlations have been determined over energy ranges of ～ 1 MeV. The distributions are compared with the predictions of random matrix theory, and good overall agreement is obtained. These result have provided new tests of the statistical theory of resonances and of the theory of isobaric analogue states. In addition, these data give the first experimental confirmation of the channel coupling required by direct reaction theory. The linear correlation coefficients are often surprisingly large (for these data sets, the average value is >0.5 ), so large in fact that the traditional DWBA treatment of direct reactions must fail in some cases. This failure is discussed with the aid of a simplified model. Tests of the Gaussian nature of reduced width amplitudes are also examined.     

Absorption mechanisms for waterborne sound in Alberich anechoic layers

The effect of replacing the viscoelastic, polymer, base layer by a metal base on the anechoic performance of an Alberich, underwater, sound absorber is reported. It is seen that anechoic performance can be retained using the metal base and it is concluded that the anechoic behaviour is primarily due to the dynamic behaviour of the cover layer.