Direct Spin Determination of On-Line-Separated Isotopes by Nuclear Orientation and Nuclear Magnetic Resonance

Abstract

Nuclear magnetic resonance of on-line-oriented nuclei is reported for the first time, in the cases of mass-separated 106 In, 108 In, and l04 Ag. Combination of the extracted g factors with independent information on the magnetic-moment values leads to unambiguous spin assignment for the high-spin ground states of I06 In and 108 In. The high-precision magnetic moments derived for these nuclei as well as the result on 104 Ag point to strong discrepancies from the additivity relation.PACS numbers: 21.10. Hw, 2U0.Ky, 23.20.En, 27.60.+J Unambiguous spin assignment to ground states of nuclei is a first requirement for reliable nuclear-structure studies. Clearly for these ground-state spin determinations, only "strong arguments" may be used. This means that one should use direct measurements which are independent of decay-scheme considerations. Incomplete and/or erroneous decay schemes have often led to a time dependence of spin assignments based on weak arguments, as, e.g., in the intensively studied cases of 106 In and ""In. 1 " 8 Unfortunately, the choice of methods for ground-state spin determinations which are in accordance with on-line separation conditions is rather limited. The atomicbeam method, which is the ideal method, suffers from low transmission rates, severely restricting its application far from stability. 9 Alternative methods rely on the resolution of the hyperfine structure. This approach may be used, for instance, in laser spectroscopy or in nuclear quadrupole resonance (NQR) spectroscopy. At high spin, though, the hyperfine patterns become highly complicated and overlapping. A clear spin assignment is obtainable when combining laser spectroscopy with rf, but then intensity problems may arise again. This particular technique is being tested for on-line use by at least one group. 10 The principle of NQR has been applied in a quadrupoleinteraction nuclear magnetic resonance on oriented nuclei (NMR-ON) experiment on 188 Ir, n but the method remains restricted to a few favorable cases.A more generally applicable direct method has been developed recently at the nuclear orientation on-line facility KOOL, where nuclear orientation of almost all isotopes produced by the combination of the CYCLONE cyclotron and the LISOL on-line separator can be achieved. 12 The NMR-ON technique, however, was applied up to now only to long-lived isotopes-a review is given by Herzog. 13 The need for high statistics and long search times made this technique to be considered incompatible with on-line working conditions. We succeeded in obtaining NMR-ON curves for ,06 In, 108 In, 104 Ag, and 189 Au m . The last case concerned the study of the high field fraction of implantation sites. 14 An NMR coil was installed around the continuously implanted sample, which was connected to the mixing chamber of a 3 He-4 He dilution refrigerator. The equipment and the acquisition method were developed and tested for on-line use. Special care was taken to eliminate the effects of varying production rates by taking the ratio W(0)/W{n/2) as th...

Magnetic moment ofAg104mand the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance o

“…5). Table I Table I. This value is in agreement with, but an order of magnitude more precise than the previous result obtained in a similar experiment by Vandeplassche et al [1]; that is, ν res = 266.3(5) MHz. It was used to determine a new precision value for the hyperfine field of Ag in Fe, as is discussed below.…”

“…Using a triangular modulation frequency of 100 Hz, a modulation bandwith of 0.5 MHz, and a RF signal level of −32 dBm, the center RF frequency was varied in steps of 0.5 MHz over the resonance search region from 263.5 to 270 MHz. The search region could be chosen so narrow because two precise and mutually consistent values are available in the literature for both the hyperfine field of Ag in Fe, that is, |B hf (AgF e)| = 44.7 T [25,34], and the magnetic moment of 104 Ag g , that is, µ = 3.92 µ N [1,2]. Two scans were performed, stepping the frequency region in both upward and downward directions, to avoid possible shifts of the (effective) resonance centers owing to a finite spin-lattice relaxation time.…”

“…For the I π = 5 + ground state the magnetic moment was determined with high accuracy in a γ -NMR/ON measurement as µ = 3.914 (8) µ N [1] and later also in an atomic beam magnetic resonance experiment; that is, µ = 3.919(3) µ N [2]. For the isomeric state, the only value for the magnetic moment that is available in the literature, that is, µ = +3.7(2) µ N [3], is not very precise though.…”

The Gamow-Teller beta decay of neutron-deficient even isotopes of tin

“…This limit is consistent with our previous result, both values being in disagreement with the one given by the Leuven group in an internal report [26] (see Table 3). Spins have been measured to be 7 [23,31] for the 58-min and 2 [-23] for the 40-rain state of l~ With respect to the three lowlying l~ states directly above the low-spin isomer, the results from various experiments [11][12][13]30] differ somewhat inassignment of level sequence and spins. These discrepancies, however, have no major influence on the GT strength distribution which we are concerned with here.…”

β-decay anisotropies of the mirror nucleiO15andFSeverijns1, Wouters2, Vanhaverbeke3 et al. 1989Phys. Rev. Lett.Self Cite40180View full textAdd to dashboardCite

“…21 The precision of the hyperfine field value can still be increased significantly (0.1% level) by using the technique of NMR-ON (nuclear magnetic resonance on oriented nuclei), which has recently been shown to be feasible in on-line conditions. 22 With the setup and analysis method as described, a relative precision of 2% on the asymmetry parameter can be obtained if the interaction pB is known rather accurately (the hyperfine field B is known with a precision better than 0.5% for a large number of elements already). Nevertheless, if one wants to extract limits for the quenching of the axial-vector coupling constant gA from experimental A\ values for mirror nuclei, it is in most cases difficult to be competitive with the usually more precise ft values, from which these limits can also be obtained.…”