Superdeformed bands in195Tl

Two superdeformed (SD) bands have been found and assigned to¹⁹⁵Tl on the basis of excitation function and cross bombardment results. The two bands are almost identical in transition energies to those observed in¹⁹³Tl. They are signature partners with a splitting, presumably due to the proton i_13/2 (=5/2) orbital, characteristic of all known SD bands in the thallium isotopes. Their alignments relative to the¹⁹³Tl bands were found to be zero.On leave from Comision National de Energia Atomica 1429 Buenos Aires, Argentina.     

Nanopowder Characterization: Challenges and Future Directions

This article summarizes the conclusions of a workshop organized at the National Institute of Standards and nobreak Technology (NIST), Gaithersburg, October 4–5, 2001. The workshop was focused on the strengths and limitations of the techniques currently used for creating stable dispersions of nanoparticles and measuring the size distribution of powders in the nanosize range. Several emerging and alternative techniques with potential for use in particle size measurement in the nanometer range were advanced. Future needs for procedural and instrumental techniques and standards were identified.     

Mode beating in spot-size converter lasers

An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper.     

The Effect of a Finite Interaction Cross-Section on the Hanle Signal

Hanle technique is used for the lifetime measurement of the atomic excited states. Field dependent Hanle signal is Lorentzian under ideal conditions. Any departure from ideal situation is reflected in the shape of the Hanle signal resulting in erroreous measurements. The effect of one such factor, a finite interaction cross section, is discussed here.     

Measurements of the Decay KL-->e+ e- mu+ mu-

The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay K(L)-->e+ e- mu+ mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be [2.69+/-0.24(stat)+/-0.12(syst)]x10(-9), with a radiative cutoff of M(2)(ee mu mu)/M(2)(K)>0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio-Isidori-Portolès (DIP) model of the K(L)gamma*gamma* vertex yields a result of -1.59+/-0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. We use this decay mode to set limits on CP and lepton violation.     

Contribution of vaporization and boiling to thermal-spike sputtering by ions or laser pulses

Here we consider what, in our terminology, we designate as normal vaporization, normal boiling, and phase explosion. In the case of vaporization, one is dealing with the emission of particles (atoms or molecules) from the extreme outer surface of either a solid or liquid for any temperature exceeding 0 K. In the case of boiling, one is (at least ideally) dealing with heterogeneously nucleated bubbles which diffuse to the outer surface of a liquid or solid and then escape, the latter being possible for temperatures equal to or exceeding the boiling temperature (T(b)). In the case of phase explosion one is dealing with the consequences of what happens when a liquid approaches the thermodynamic critical temperature (T(tc) or T(c)), and massive homogeneous nucleation takes place. Although these three mechanisms have been reviewed in reasonable detail in recent work, we will here present evidence, apparently not previously considered, that boiling, whether the distance scale is atomically small (5-15 nm, as for laser-pulse impact on a metal in the absence of thermal diffusion) or much larger, has a prohibitive kinetic obstacle because it requires bubble diffusion if the bubbles are formed other than at the outer surface. That is to say, boiling will never be a significant process whether with ion or laser-pulse impact. This leaves vaporization and phase explosion as the only possible thermal-spike processes capable of expelling material from an ion- or laser-pulse bombarded surface in a significant quantity. But even with vaporization it can be shown that a kinetic obstacle, although not as severe as for boiling, will enter. The final result is that only phase explosion will normally be relevant for sufficiently short time scales.     

The work function of hydrothermally synthesized UO2 and the implications for semiconductor device fabrication

The photoelectric work function of nearly stoichiometric (111) and (100) hydrothermally grown UO₂ was measured to be 6.28 ± 0.36 eV and 5.80 ± 0.36 eV, respectively. Candidate metals for electrical contacts are identified for both rectifying and non‐rectifying contacts based on work function, lattice compatibility, and electrical conductivity.