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Featured researches published by W. Knauer.


Hyperfine Interactions | 1979

The12C(2 1 + ) state as probe for transient magnetic fields in polarized iron

G. J. Kumbartzki; K. Hagemeyer; W. Knauer; G. Krösing; R. Kuhnen; V. Mertens; K.-H. Speidel; J. Gerber; W. Nagel

PAC measurements on the 4.43 MeV12C(2+) state on recoil in magnetized iron at velocitiesvion=2.1v0, 6.0v0, 7.4v0 yield integral precession angles of ϕ=+0.72(18), +0.94(16) and +0.71(18) mrad, respectively. The results supplementary to existing precession data are interpreted by a distribution of C5+ ions implying a K-shell polarization of ≃28% and an effective charge larger than measured after emergence from the solid. The low-velocity precession tends to disagree with the empirical law of linear relationship between transient field and ion velocity. The presence of molecular orbital effects is discussed.


Physics Letters A | 1980

Evidence for K-shell polarization of C-ions in ferromagnets via molecular-orbital promotion

K.-H. Speidel; Gerfried J. Kumbartzki; W. Knauer; G. Krösing; V. Mertens; P. N. Tandon; J. Gerber; R.M. Freeman; M.B. Goldberg

Abstract Transient field precessions of the 12 C 4.43 MeV state in polarized Fe and Ni are found to scale with the polarized electron density of the hosts at υ ion = 4.1 υ 0 , but are comparable at υ ion = 2.1 υ 0 . The latter is attributed to direct K-shell polarization of carbon via molecular-orbital promotion.


Physics Letters A | 1976

Can projectiles traversing solids bind electrons at all velocities

M.B. Goldberg; E. Konejung; W. Knauer; Gerfried J. Kumbartzki; P. Meyer; K.-H. Speidel; J. Gerber

Abstract PAC measurements on the 4.43 MeV 12 C(2 + ) state on recoil in magnetized iron at velocities υ ion = 0.058 c , 0.071 c yield integral nuclear precession angles of Φ = −0.18 (30), +0.17 (39) mrad respectively. Evidently, the high electron-spin-polarization transfer to the innermost carbon orbits implied by a previous measurement (υ ion = 0.03 c , Φ = +0.85 (14) mrad) is suppressed at higher ion velocities.


Physics Letters A | 1980

K-shell polarization of O ions in ferromagnets by spin dependent electron promotion via molecular orbitals

J. Gerber; R.M. Freeman; K.-H. Speidel; Gerfried J. Kumbartzki; W. Knauer; V. Mertens; P. N. Tandon; M.B. Goldberg

Abstract Transient field precessions of the 6.13 MeV 16 O(3 - ) state have been measured in polarized Fe and Ni in order to corroborate our earlier results on C ions. It is found that precessions in Fe and Ni scale with the polarized electron density of the host at v ion = 3.0 v 0 and are comparable at v ion = 1.5 v 0 . The latter is attributed to direct K-shell polarization of the ion by spin dependent electron promotion via molecular orbitals.


Nuclear Physics | 1980

Hyperfine interaction and g-factor measurements in Er isotopes

K.-H. Speidel; Gerfried J. Kumbartzki; W. Knauer; R. Kuhnen; G. Kraft; J. Gerber; M.B. Goldberg; G. Goldring; A. Zemel

Abstract Energy levels in 160 Er and 159 Er were excited in the reactions 28 Si( 136 Xe, 4n) 160 Er and 28 Si( 136 Xe, 5n) 159 Er, and the product nuclei, recoiling with a velocity v = 0.07 c were stopped in a plunger instrument after traversing a volume of hydrogen gas. The angular distribution of de-excitation γ-rays was studied as a function of flight time and gas pressure. Appreciable perturbations were detected in 160 Er at times as short as 2 ps and in an angular momentum region as high as 12ħ. No perturbation could be detected in the 21 2 + level of 159 Er even after 12 ps, signifying a low value for the g -factor of this level.


Nuclear Instruments and Methods | 1979

A curved plunger for time-differential PAC measurements on recoil into gas

M.B. Goldberg; W. Knauer; R. Kuhnen; G. J. Kumbartzki; H.-D. Rosendaal; K.-H. Speidel; J. Gerber; F. Kuntz

Abstract For a time-differential study of the hyperfine interaction on nuclear high spin states in highly ionized atoms recoiling into gas, a target-plunger was constructed having a well-defined curvature under gas pressure. Its perfect operation in this geometry is demonstrated by remeasuring lifetimes of excited states in 160 Er which were populated in the reaction 28 Si( 136 Xe, 4n) 160 Er with 632 MeV Xe-projectiles.


Hyperfine Interactions | 1978

PRECESSION MEASUREMENTS ON NUCLEAR-EXCITED C-, O- AND F- IONS RECOILING IN POLARIZED IRON AND NICKEL

M.B. Goldberg; W. Knauer; G. Kumbartzki; K.-H. Speidel; J. C. Adloff; J. Gerber


Hyperfine Interactions | 1981

Transient fields at16O nuclei recoiling in polarized iron and nickel

K.-H. Speidel; Gerfried J. Kumbartzki; W. Knauer; V. Mertens; P. N. Tandon; J. Gerber; R. M. Freeman


Hyperfine Interactions | 1978

Enhanced transient fields at56Fe,110Cd recoiling in iron and the94Zr (2 1 + ) g-factor

J. Gerber; M.B. Goldberg; W. Knauer; G. Kumbartzki; K.-H. Speidel


Hyperfine Interactions | 1981

Transient field precessions from spin dependent electron promotion via molecular orbitals

K.-H. Speidel; Gerfried J. Kumbartzki; W. Knauer; V. Mertens; P. N. Tandon; M. B. Goldberg; J. Gerber; R. M. Freeman

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