The magnetic moment of the first excited state of 19O

The magnetic moment of the first excited 96 keV, $\text{3}\text{2}{}^{\mathrm{+}}$ state of ¹⁹O has been determined by an integral perturbed angular correlation measurement in a transverse external magnetic field. The value obtained for the g-factor, ?0.48(6), is discussed in terms of shell-model configurations. The wave function of the $\text{3}\text{2}{}^{\mathrm{+}}$ level is shown to consist mainly of the $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^3$ configuration.     

Total synthesis of (+/-)-phomactin G, a platelet activating factor antagonist from the marine fungus Phoma sp

A total synthesis of phomactin G (), which is a central intermediate in the biosynthesis of phomactin A () in Phoma sp. is described. The synthesis is based on a Cr(ii)/Ni(ii) macrocyclisation from the aldehyde vinyl iodide, leading to, followed by sequential conversion of into the [small beta]-epoxide and the ketone which, on deprotection, led to (+/-)-phomactin G. Phomactin G () shares an interesting structural homology with phomactin D (), the most potent PAF-antagonist metabolite in Phoma sp. It is most likely converted into phomactin A (), by initial allylic oxidation to the transient [small alpha]-alcohol 'phomactin' structure, known as Sch 49028, followed by spontaneous pyran ring formation.     

Cytotoxic alkaloids motuporamines A-C: synthesis and structural verification

[formula: see text] The unusual structure and biological properties of the marine alkaloids motuporamines A-C, as well as the uncertainty as to the position of the olefin within the ring of motuporamine C, led us to synthesize these compounds. The strategy utilized the ring-closing metathesis reaction to form the 14- and 15-membered rings and Michael addition and amidation chemistry to introduce the spermine-like unit. The syntheses, structure assignment verifications, and also the determination of the position of the olefin in motuporamine C are described.     

The tilted-multifoil hyperfine interaction and nuclear spectroscopy

Ions emerging from a stretched foil with their velocity vectorv at an oblique angle to the normaln (tilted foil geometry) are known to be polarized along the axisv×n. The electronic polarization of atomic configurations can influence the nucleus during flight in vacuum via the hyperfine interaction. For a large number of polarizing foils and for very short interaction times, the resulting effects resemble a pure precession in an external magnetic field and have been used to measureg-factors of short-lived nuclear high-spin levels. For long interaction times, a net nuclear polarization is induced and has so far been utilized to determine signs of nuclear quadrupole moments of high-spin isomers and to investigate parity nonconservation effects in⁹³Tc.     

Magnetic moments of mirror nuclei with tilted-foil polarization

We report here on an ongoing experimental program initiated at the ISOLDE facility at CERN for the measurement of magnetic moments of short-lived radionuclides, with the emphasis on magnetic moments of mirror nuclei in far-from-stability regions. The nuclei are polarized by the tilted foil technique and the resulting 0–180^○ βasymmetry is monitored as a function of rf frequency applied in an NMR setup. In order to achieve sufficiently high energy for transmission through the foils, the experimental setup is mounted on a high voltage platform. The first experiment in this program was the measurement of the βasymmetry and the NMR resonance for the ground state of ²³Mg (I=3/2, T_1/2=11.3 s), yielding μ=−0.533(6) nm. Improvements to the experimental setup are presently being designed, to be used in conjunction with the new developments at ISOLDE for obtaining high charge-state ions from the EBIS (REX-ISOLDE) ion source. This will help pave the way for measurements of magnetic moments of T=3/2 nuclei in the s–d shell and of T=1/2 f-shell nuclei. The study of relaxation times and other solid-state phenomena in semiconductors and other materials of interest using this technique is also contemplated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heavy ion beam polarization produced by the multi-tilted-foil interaction

Nuclear polarization of the 7/2^? ground-state of⁵¹V was produced via the Multi-Tilted-Foil (MTF) interaction with a V beam. The induced polarization was determined by measuring the left-right asymmetry of Coulomb excited⁵¹V nuclei and, for a⁵¹V beam at E=100 MeV, was measured to beP _I =0.012(2). The nuclear polarization was also induced atE=50 MeV and, after further acceleration, determined at E=195 MeV to be P_I=0.010(1). These experiments demonstrate the feasibility of polarizing a great variety of heavy-ion beams at arbitrary velocities with subsequent acceleration and passage through magnetic beam-optics elements. Such polarization, albeit small, can be utilized for the determination of electromagnetic moments of exotic beams and separated reaction products.     

Parity violation in the 17/2− isomer of93Tc

The parity-violating mixing of the 17/2^? and 17/2⁺ levels in⁹³Tc nuclei, polarized by the tilted multifoil interaction, was measured by the observation of the forwardbackwardγ-ray asymmetry. The asymmetry was determined to beA _γ=1.18(48)×10^?3. The nuclear polarization was determined in a measurement of the quadrupole interaction in a⁹²Mo isomer and the parity violation matrix element 〈H _PV〉 is found to be ¦〈H _PV〉¦ =0.8(4) meV.