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861.
B. Hitti S. R. Kreitzman T. L. Estle R. L. Lichti K. H. Chow J. W. Schneider C. D. Lamp P. Mendels 《Hyperfine Interactions》1994,86(1):673-679
The radio frequencySR technique developed at TRIUMF was used to measure the temperature dependence of the diamagnetic muon, Mu, and Mu* amplitudes in silicon between 10 K and 500 K. Six samples doped with phosphorus (n-type) and boron (p-type) in the concentration range 1011 to 1015 cm–3 were studied. In pure Si a very good fit over the whole temperature range is obtained from a model that includes the ionization of Mu* and Mu to a bond centered
+ followed at high temperature by charge exchange involving Mu. 相似文献
862.
Richard Ley D. Hagena D. Weil G. Werth W. Arnold H. Schneider 《Hyperfine Interactions》1994,89(1):327-341
Electric dipole transitions in the microwave range have been induced between the fine-structure levels of positronium in the excited staten=2. As an indication of the transitions, we used the increase in Lyman- radiation when the metastable 23S1-level is depopulated. The results for the transitions 23S123P0,1,2 are
0=18499.65±1.20±4.00 MHz,
1=13012.42 ±0.65±1.54 MHz and
2=8624.38±0.54±1.40 MHz. The first error is statistical and the second systematic. The precision of the present measurement has improved by a factor of 3, compared to previous data. Recent bound state QED-calculations have been extended to the orderR
t8
4ln
–1. The not yet completely calculated orderR
t8
4 is estimated to contribute less than 1 MHz. Our experimental results are in good agreement with theory. By applying a weak magnetic field, we were able to observe the transition 23S121P1 which is strictly forbidden byC-invariance in zero field. Our result, corrected for Zeeman- and motional Starkeffect, is
3=11180.0±5.0±4.0 MHz. An upper limit for theC-violating matrix element of
MHz could be deduced. Our experiment used moderated slow positrons from the bremsstrahlung and pair production of a pulsed electron linear accelerator (TEPOS facility at the university of Giessen). 相似文献
863.
O. Hartmann E. Karlsson R. Wäppling L. Asch S. Henneberger G. M. Kalvius A. Kratzer H. -H. Klauß F. J. Litterst M. A. C. De Melo 《Hyperfine Interactions》1994,85(1):251-258
We have studied the muon precession frequency in a ferromagnetic single crystal of Gd metal. The overall features of our findings are compatible with earlier results on polycrystalline material. In the temperature region between 245 and 220 K where the Gd magnetization starts to turn away from the c-axis, we observe an increase in the muon depolarization rate, and a complex precession signal which can be separated into two frequency components meaning that spin turning does not occur simultaneously in different parts of the sample (domains). From these more detailed data follows that previously obtained values forB
fc andB
dip can not both be correct. Two explanations for our new result are possible: EitherB
fc undergoes a change around 230 K which is directly coupled to the spin turning angle, or the value of the dipolar field contribution used in the earlier evaluation is too low. This imposes some uncertainty as to the value of the angle at the onset of spin turning derived fromSR frequencies. 相似文献
864.
R. Kadono J. H. Brewer K. Chow S. R. Kreitzman Ch. Niedermayer T. M. Riseman J. W. Schneider T. Yamazaki 《Hyperfine Interactions》1994,85(1):259-264
The electric quadrupole interaction of55Mn nuclei was studied in the weakly ferromagnetic system MnSi using muon level-crossing resonance (LCR) technique. The temperature dependence of the electric field gradient (EFG) shows a critical behavior near the ferromagnetic transition temperature, indicating that the EFG due to the conduction electron is strongly correlated with the magnetic susceptibility in the itinerant electron magnetism. The temperature dependence of EFG is in reasonable agreement with the self-consistent renormalization theory developed by Moriya and coworkers.We gratefully acknowledge helpful discussion with Dr. N. Nishida. We also wish to thank Keith Hoyle and Curtis Ballard for technical support. 相似文献
865.
W. M. Reiff B. D. James M. Bakalova J. Liesegang A. H. White B. W. Skelton D. C. R. Hockless 《Hyperfine Interactions》1994,94(1):2081-2086
Iron-57 Mössbauer spectroscopic results for a new series of related chloroferrate salts of complex ammonium cations are presented. In particular, spectra of materials based on FeCl
4
–
, FeCl
5
2–
, FeCl
6
–
, [FeCl5(H2O)]2–, and [FeCl5(CH3OH)]2– anions are discussed relative to the systematics of their isomer shifts, coordination numbers, and low temperature 3D critical ordering temperatures. The following specific systems have been studied by Mössbauer spectroscopy and definitively characterized by single-crystal X-ray analysis: [CH3NH
3
+
]4[FeCl6]3–[Cl–](A), [Me2N(-CH2CH2)2NMe
2
+
][FeCl
5
2–
] (B), [H3NCH2CH2NH
3
2+
][FeCl5·H2O2–], (C), and [NH3(CH2)6NH
3
2+
]4[(FeCl
6
3–
)(FeCl
4
–
)ClCl
4
–
] (D). The spectral data for these complexes are considered in the light of results of previous studies for systems such as [K2FeCl5·H2O], [Co(NH3)6][FeCl6], diamethyltriethylenediammoniumpentachloroferrate (E), and the related [FeCl5·CH3OH]2– salt (F). The critical 3D ordering temperatures are 1.45, 6.80, 3.45, and 1.22K forA, B, C, andD, respectively. 相似文献
866.
C. Böttger S. J. Campbell W. Stieler F. L. Litterst J. Hesse 《Hyperfine Interactions》1994,94(1):2279-2286
A detailed analysis of room temperature57Fe Mössbauer spectra ofAuFe (5 at.% Fe) andCrFe (5, 10 at.% Fe) samples is presented. The deviation from Lorentzian line shape observed in the spectra indicates both thickness effects and structural disorder in these systems. The thickness effect has been taken into account using a new fitting technique that solves the transmission integral numerically rather than relying on the thin absorber approximation. The present results and analyses using both the thin absorber approximation and the full transmission integral methods on these alloy systems are compared with earlier results obtained on these alloy systems using only the thin absorber approximation. 相似文献
867.
The classicalR-matrix structure for then-particle Calogero-Moser models with (type IV) elliptic potentials is investigated. We show there is no momentum independentR-matrix (without spectral parameter) whenn 4. The assumption of momentum independence is sufficient to reproduce the dynamicalR-matrices of Avan and Talon for the type I, II, III degenerations of the elliptic potential. The inclusion of a spectral parameter enables us to findR-matrices for the general elliptic potential. 相似文献
868.
M. Leino J. Uusitalo T. Enqvist K. Eskola A. Jokinen K. Loberg W. H. Trzaska J. Äystö 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(2):151-152
Two new neutron-deficient isotopes207,208Ac have been produced in fusion reactions with 5.2–5.6 MeV/nucleon40Ar ions on175Lu and identified on the basis of genetic correlations. The fusion evaporation products were separated on-line using a gas-filled magnetic recoil separator. The alpha energy and half-life of208Ac were determined to be (7572±15) keV and (95 ?16 +24 ) ms, respectively. A new alpha line with a half-life of (25 ?5 +9 ) ms and an energy of (7758±20) keV is assigned to the decay of an isomeric state in208Ac. Another new activity with a half-life of (22 ?9 +40 ) ms and an alpha energy of (7712±25) keV is assigned to207Ac. 相似文献
869.
A. Schröter E. Berdermann H. Geissel A. Gillitzer J. Homolka P. Kienle W. Koenig B. Povh F. Schumacher H. Ströher 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):101-113
Subthreshold ¯p andK
– and energetic
– production was studied in Ne + NaF, Cu, Sn and Bi, and in Ni + Ni collisions with incident energies between 1.6 and 2 GeV/u. The measured cross sections indicate a dominant contribution of baryonic resonances. This is also consistent with a generalized scaling behaviour of the cross sections with the energy available in the collision and the energy necessary to produce particles as observed with Ne induced reactions. Deviations from scaling especially pronounced in the Ni-Ni system will be discussed in terms of absorption effects. The flat slope of the excitation function for ¯p production can be related to a reduced production threshold caused by a reduction of the antiproton mass in the dense and heated medium by about 100—150 MeV/c2. A similar in-medium mass reduction is also indicated forK
– mesons. An increased ¯p reabsorption probability for the heavier systems is concluded from the comparison of the ¯p yields in Ne + NaF, Ne + Sn and Ni + Ni collisions.Dedicated to Professor Klaus Dietrich on the occasion of his 60th birthday. 相似文献
870.
T. George S. Saupe M. H. Wappelhorst W. Urban 《Applied physics. B, Lasers and optics》1994,59(2):159-166
We present a very high-resolution heterodyne spectrometer based on a CO laser which operates down to fundamental-band transitions of the molecule. This allows us to detect saturated absorption signals on these transitions at very low pressure (0.4 Pa) and laser intensity (< 1 mW/cm2), yielding a linewidth of about 250 kHz. With the CO fundamental-band laser stabilized to these saturation signals we have measured the transition frequencies of the fundamental bands of three isotopic species to an accuracy of typically 20 kHz (v/v 3 × 10–10), referenced to the CO2 frequency standard. Together with additional frequency measurements of the first hot bands, these provide the first heterodyne frequency data of sub-Doppler accuracy for transitions in low lying bands of CO. They now represent the most accurate secondary frequency standard in the spectral region around 5 µm (60 THz). 相似文献