A precise PKPβ+ measurement at Z = 55: (I). The mass of 130Cs

The Q-value for the ¹²⁹Xe(³He, d)¹³⁰Cs reaction is measured to be +5 ± 20 keV. By combining this result with the known neutron separation energy of ¹³⁰Xe, we derive the total decay energy of ¹³⁰Cs

¹³⁰Xe to beQ_EC = 2974 ± 20 keV. This value agrees well with two previous positron end-point measurements but disagrees with the corresponding value derived from the 1977 atomic mass evaluation. This has significance in testing the accuracy of the calculated ratio for ¹³⁰Cs decay. The mass excess of ¹³⁰Cs is derived to be ?86908 ± 14 keV. An excited state in ¹³⁰Cs. was also identified at 121 ± 15 keV with J < 3 and positive parity. The Q-value for ¹³⁶Xe(³He, d)¹³⁷Cs was measured to be 1918 ± 12 keV.     

Hypochromism and optical rotation in helical polymers

We show that the decreased light absorption and the anomalous optical rotatory dispersion in helical polynucleotides and polypeptides may be interpreted purely as a local field effect. The electric field of the incident light wave is screened off from each residue by the induced electric dipoles in the others. Quantum-mechanical calculations based on time-dependent Hartree theory and this local field picture correspond precisely with the formulae derived in Tinoco's, Rhodes's, and Moffitt's exciton theories, provided that the Coulomb interactions are small. The degenerate exciton waves in our theory correspond to normal modes of a set of coupled oscillators, and the rotational strengths and oscillator strengths are conserved. There is no conflict between Tinoco's theory of hypochromism and the ones proposed by Bolton and Weiss and by Nesbet. One new conclusion is that the energy shifts accompanying hypochromism should not vary much when the exciton coupling changes from the strong to the weak coupling limits.     

Properties of Quantum Languages

The class of quantum languages Q() over an alphabet is the class of languages accepted by quantum automata. We study properties of Q() and compare Q() with the class of regular languages R(). It is shown that Q() is closed under union, intersection, and reversal but is not closed under complementation, concatenation, or Kleene star. It is also shown that Q() and R() are incomparable. Finally, we prove that L Q() if and only if L admits a transition amplitude function satisfying a certain property and a similar characterization is given for R().     

Precision branching ratio measurement for the superallowed beta+ emitter 62Ga and isospin-symmetry-breaking corrections in A>or=62 nuclei

A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta+ decay of 62Ga were identified, establishing the dominant superallowed branching ratio to be (99.861+/-0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6+/-1.4 s for 62Ga decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A>or=62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays.     

Aggregated colloids under flow

Summary We have recently reported on a new scaling theory of the rupture of colloid aggregates. The scaling theory is compared with a simulation study of the transient response of sheared 2d aggregates. In this paper we discuss the origins of deviations from the predicted scaling behaviour. We also report some of the steady-state configurations formed post rupture. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

First measurement of the double spin asymmetry in (-->)e(-->)p-->e(prime)pi(+)n in the resonance region

The double spin asymmetry in the (-->)e(-->)p --> e(prime)pi(+)n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2 = 0.35-1.5 GeV(2). Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity-1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q(2) of the helicity asymmetry A1 for the F(15)(1680) resonance than expected from the analysis of the unpolarized data.     

High-spin structure of N\simeq Z nuclei around the A = 72 region

High-spin states have been studied in ⁷²Kr and ⁷²Br using the ⁴⁰Ca + ⁴⁰Ca and ³⁶Ar + ⁴⁰Ca reactions at 164 and 145 MeV, respectively. The properties and configurations of the high-spin bands observed have been interpreted using unpaired cranked Nilsson-Strutinsky (CNS), and for ⁷²Kr, paired cranked relativistic Hartree-Bogoliubov (CRHB) calculations. In ⁷²Kr a new band has been identified that has the properties expected for the doubly aligned S-band configuration. In ⁷²Br the previously known bands have been extended to higher spin. This has lead to a re-interpretation of the configurations.Received: 31 October 2002, Published online: 24 February 2004PACS: 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.50. + e      

Measurement of the proton spin structure function g1(x,Q2) for Q2 from 0.15 to 1.6 GeV2 with CLAS

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q2) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q2)= integral g(1)(x,Q2) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q2 region. A rapid change in Gamma(1) is observed for Q2<1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value.