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21.
Abele H Astruc Hoffmann M Baessler S Dubbers D Glück F Müller U Nesvizhevsky V Reich J Zimmer O 《Physical review letters》2002,88(21):211801
We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error. 相似文献
22.
D. Dubbers K. Dörr H. Ackermann F. Fujara H. Grupp M. Grupp P. Heitjans A. Körblein H. -J. Stöckmann 《Zeitschrift für Physik A Hadrons and Nuclei》1977,282(3):243-248
Multiple quantum nuclear magnetic resonance (NMR) transitions were observed on polarized8Li nuclei, which were produced by capture of polarized neutrons in a single crystal of LiTaO3. The asymmetric8Liβ-radiation distribution was used for the detection of NMR. A quadrupole moment ratio ¦Q(8Li)/Q(7Li)¦=0.78(1) was determined. Saturation of multiple quantum transitions in nuclear radiation detected NMR may lead to a reduction in measuring time of up to two orders of magnitude, as compared to single quantum detection methods. The measured spectra agree well with an exact lineshape calculation. The same measurements were also performed on a LiTaO3 powder sample. This was done to test a method to obtain quadrupole coupling constants from high field NMR multiple quantum powder patterns, which are easily detectable, also for higher nuclear spins. This latter method may be applicable also to conventional NMR detection techniques. 相似文献
23.
H. -J. Stöckmann H. Ackermann D. Dubbers M. Grupp P. Heitjans 《Zeitschrift für Physik A Hadrons and Nuclei》1974,269(1):47-57
Polarized20F nuclei (T 1/2=11s,I=2) have been produced in a tetragonal MgF2 single crystal by capture of polarized neutrons. Nuclear magnetic resonance transitions have been induced and observed via the asymmetricΒ decay to20Ne, yielding the quadrupole coupling constant ¦e 2 q Q/h¦=5.77(2)MHz, the quadrupole moment ¦Q(20F)¦=0.064(12) b and the asymmetry parameter of the electric field gradientη=0.317(2). In order to study possible lattice defects produced by the recoil displacement due to the captureγ-rays NMR signals were registered both at room temperature and at 12 K. Width and depth of the resonance curves indicated that at room temperature nearly all20F ions occupy normal lattice sites with an undisturbed environment. At 12 K, however, where no annealing occurs, this is only true for about half of the20F ions which are stopped directly at defect free sites. The other half of the20F ions at 12 K shows resonance frequencies shifted by defect interactions up to the order of some 100 kHz. Furthermore two simple methods are reported which allow a quick estimate of the strength of the quadrupolar interaction: (1) observation of theΒ decay asymmetry versus the magnetic field strength (decoupling curve), (2) broad-band modulation of the inducedrf field and observation of theΒ asymmetry versus the depth of the modulation. 相似文献
24.
An experimental arrangement for ns lifetime measurements in nuclear reactions is briefly described. The half-life of the level at 208.1 keV in 171Lu has been determined in the reaction 169Tm(, 2n) 171Lu as
. Delayed and populating γ-ray spectra have been measured, applying the method of delayed γ-γ coincidences. In the radioactive decay of 173Hf, the lifetime of the level at 425.1 keV in 173Lu has been measured as
. Comparisons with Weisskopf and Nilsson estimates have been performed taking into account pairing correlations. A modified Nilsson Hamiltonian has been used. The dependence of El transition probabilities between the states
and
on the difference of the initial- and final-state deformations is studied. Qualitative agreement with semi-microscopic calculations of equilibrium deformations is found. Lifetimes of the
states are estimated. 相似文献
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26.
D. Dubbers 《Hyperfine Interactions》2000,127(1-4):355-363
Recent years have seen significant progress in the development of neutron polarizers and polarization analysis, due, in particular,
to the work done by the Mainz group. A number of new experiments with polarized neutrons will be discussed, both from the
fields of neutron particle physics and of magnetism. Further recent work on neutrino mass measurements will be reviewed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
27.
Ignatios Antoniadis GRANIT workshop organizer Stefan Baessler GRANIT workshop organizer Orfeu Bertolami GRANIT workshop organizer Dirk Dubbers GRANIT workshop organizer Alexander Meyerovich GRANIT workshop organizer Valery Nesvizhevsky GRANIT workshop organizer Konstantin Protasov Serge Reynaud 《Comptes Rendus Physique》2011,12(8):703-706
28.
D. Dubbers 《Zeitschrift für Physik A Hadrons and Nuclei》1979,293(3):211-217
Several problems from radio-frequency spectroscopy of atoms and nuclei are treated with irreducible spin precession theory. In the first part, effective field techniques are used to derive analytically single and multiple quantum double resonance lineshapes for atoms with a hyperfine structure in a high magnetic field. In the second part (as an extension to previous work), nuclear resonance signals are calculated for oriented nuclei subject to an electric hexadecapole interaction. Lineshapes of acoustically driven hexadecapole transitions are derived in closed form and compared to experiment. Further, multiple quantum NMR transitions within a hexadecapole shifted nuclear Zeeman structure are calculated, and some distinct features of hexadecapole effects on NMR lineshapes are pointed out. This last case is of current interest due to recent progress in NMR-line narrowing techniques. — In the Appendix, we give lineshape equations for single and double quantum NMR transitions on oriented (I=1)-nuclei subject to an electric quadrupole interaction; these equations are also being used in the atomic rf-spectroscopy calculations. The equations are exact to all orders of the interaction with the external fields. 相似文献
29.
Baldo-Ceolin M. Benetti P. Bitter T. Bobisut F. Calligarich E. Dolfini R. Dubbers D. El-Muzeini P. Genoni M. Gibin D. Gigli Berzolari A. Gobrecht K. Guglielmi A. Last J. Laveder M. Lippert W. Mattioli F. Mauri F. Mezzetto M. Montanari C. Piazzoli A. Puglierin G. Rappoldi A. Raselli G. L. Scannicchio D. Sconza A. Vascon M. Visentin L. 《Zeitschrift fur Physik C Particles and Fields》1994,63(3):409-416
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