Using a new bunched-beam technique in the GSI heavy-ion experimental storage ring (ESR), we performed precision laser spectroscopy on relativistic heavy ions in the hitherto inaccessible infrared optical region. We determined the wavelength of the M1 transition between the F 1 ͑t ഠ 50 ms͒ and F 0 hyperfine states of the 1s ground state of hydrogenlike 207 Pb 811 . Comparing the result of 1019.7(2) nm with very recent theoretical predictions concerning QED and nuclear size contributions, a disagreement of 4.5 nm is found. Since the nucleus of 207 Pb 811 is well described by the single-particle shell model, uncertainties in nuclear corrections are expected to be small. [S0031-9007(98)07624-8] PACS numbers: 32.30.Jc, 12.20.Fv, 21.10.Ky The hyperfine splitting (HFS) of the 1s ground state of one-electron, two-body (hydrogenlike) system is the simplest and most basic magnetic interaction in atomic physics. In hydrogen the splitting is measured to thirteen significant figures, considerably more precise than the six-digit precision of the theoretical calculations of this quantity [1]. These calculations solve the Dirac equation and then add corrections for the effects of the finite size of the nuclear charge and magnetization as well as for the QED effects of self-energy and vacuum polarization. While the QED contributions are of the order of 10 26 to 10 25 for a single proton, these corrections are several percent in hydrogenlike ions of large Z in which the electron experiences exceptionally intense electric and magnetic fields. Thus measurements of the spectra of these systems can stringently test theoretical calculations of QED and nuclear effects.Recently the 1s ground state transitions in high-Z, hydrogenlike ions have become accessible to optical spectroscopy at the experimental storage ring (ESR) at GSI-Darmstadt and at the electron beam ion trap Super-EBIT at Lawrence Livermore National Laboratory. Measurements of the ground state hyperfine splittings of 209 Bi 821 at GSI [2] and 165 Ho 661 at LLNL [3] have stimulated a large number of theoretical calculations of the wavelengths of these transitions [4][5][6][7][8][9][10][11][12][13][14][15]. Discrepancies are fond between theory and experiment for both 209 Bi 821 and 165 Ho 661 .The calculations for bismuth yield a value 1 nm ͑5 3 10 23 ͒ larger than the measured value. On the basis of the precisions assigned to the corrections this discrepancy is significant, but corrections for the nuclear effects vary considerably depending upon how much the nuclear core is assumed to be polarized. For holmium, a smaller discrepancy between the calculated and measured values is reported [3], but the theoretical analysis did not take into account nuclear polarization [15] which is expected to contribute significantly.In view of this unsatisfactory situation we measured the 1s ground state hyperfine transition of 207 Pb 811 . We chose this nucleus because it is well described by the single-particle model. The magnetic moment has been measured with high precision in the ato...

The crystal structures obtained by X-ray methods of (tertbutoxy)alane and -gallane (tBuOMH2) are isotypic and are composed of discrete centrosymmetric dimers. The dimers !rise from almost symmetrical Al-0-A1 [1.810(3), 1.815 (3) A] and Ga-0-Ga [1.902(9), 1.908(9) A] bridges forming a central rhombohedra1 four membered M202 cycle [ 0 -A l -0 81.0(2)', 0 -G a -0 ?8.6(5)'] with the metallic atoms in a distorted tetrahedral environment. When one of the hydride ligands on the metals is further substituted by tert-butoxy, Very recently the synthesis and crystal structure determination of bis(tert-buty1)methoxyalane (tBu2HC-0-AlH2) and the corresponding gallane were described['? We have independently studied quite similar compounds. Our intention has been to "bridge" the structural gap between AlH3r21 and AI(O~BU), [~] with the missing mixed compounds, e.g. tBuOAlH, and (tBuO),AlH, and to examine the homologous gallium compounds. We were interested in the structures of these compounds because we had used them in CVD processes [4]. A profound synthetic work on the aluminium compounds has already been published in 1968 by Noth and Suchyf51, and some predictions of structures were made on the basis of IR spectroscopy and molecular weight determinations.The synthesis of the compounds tBuOMH, and (tBuO),MH (M = Al, Ga) was achieved by alcoholysis of diethyl ether solutions of alane and gallanef51 [equation (l)].The correct stoichiometry of the reaction is important for obtaining the desired products and the yields have been very satisfactory. The products were isolated by sublimation and crystallization. tBuOAIHz and tBuOGaHz show very simple NMR spectra in solution: in the 'H-NMR spectrum, the tert-butyl group exhibits a singlet, and in the 13C-NMR spectrum two lines for the pnmary and quaternary carbon atoms are detected. The 'H and I3C-NMR spectra of (tBuO),AlH and (tBuO),GaH are much more complex. In each case two sets of two signals of equal intensity were found that can be attributed to four chemically different tert-butyl groups. In the aluminium denvative, the ratio of the sets of signals is approximately 45:55, whereas it is 33:66 in the case of gallium derivative. We tentatively ascribed the four signals in the 'H-NMR spectra to a mixture of cis and trans isomers [cis and trans refer to the position of the hydrides with respect to the M202 central ring (see structure below)]. The trans isomer presumably leads to higher intensities. The chemical shifts of the signals change with the temperature of the formation of (tBuO),AlH and (tBu0) the NMR probe, but no changes of the intensities or a coalescence phenomenon have been All four compounds are dimeric in benzene, as found by cryoscopy.The data for the X-ray structure determination on single crystals of tBuOMH, and (tBuO),MH (M = Al, Ga) have been assembled in Table 1; the most important bond lengths and angles are summarized in Table 2t7]. As a result of the structure analyses, the molecule tBuOAIHz (tBuOGaH, is isotypic) has been depicted in Figure 1, and the mol...

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Bis(tert‐butoxyaluminum dihydride) (tBuOAlH2)2 decomposes on metal surfaces heated to 250 °C (Fe, Ni, Cu, Pt) and under reduced pressures of 0.01−0.1 atm with elimination of dihydrogen and isobutene to form a glasslike, amorphous film, which is composed of equimolar parts of hydrogen, aluminum and oxygen (elemental analysis, EDX analysis). The gases eliminated during this process were characterized by mass spectroscopy (H2, isobutene) or by infrared matrix techniques (isobutene). The exclusive binding of hydrogen to aluminum is deduced from IR spectroscopy of the HAlO film and of its deuterated form DAlO. The HAlO layer (which shows no X‐ray diffraction pattern), when heated to 450 °C or when exposed to a CO2 laser, loses hydrogen and transforms to an almost stoichiometric composite with nanoscale crystalline aluminum and aluminum oxide (Al/Al2O3) as ingredients. This transformation may be followed by IR spectroscopy, by 27Al MAS NMR or by XPS, the latter showing different signals (Al, 2p electrons, Mg‐Kα, θ = 0°) for HAlO (74.2 eV) and for the composite (Al: 72.1 eV, Al2O3: 75.3 eV). Microstructures that are characterized by different chemical compositions and different optical contrasts of the “drawing”, relative to the surrounding matrix, may be generated with an X/Y‐table and a CO2 laser. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Levels inHg have been studied by the Pt(n, 4n) reaction and the high-spin level scheme of ' Hg has been considerably extended. Backbending in both positive and negative parity yrast level sequences is discussed within the cranked shell model description. ' NUCLEAR REACTIONS '96Pt(n, 4n), E =48.6 MeV; measured E, I (9), ' t~y2(y), y-y coin; ' Hg deduced high-spin levels, J, 7r.The high-spin level spectra of the transitional Hg nuclei, both even and odd 3, have been intensively studied. ' ' The even-parity yrast levels of ' ' '' ' ' Hg exhibit, in the vicinity of I = 10, acute backbending behavior that has been attributed to the intersection of the ground bands by either 7rh~~y2 or vi~3'' rotation-aligned S bands. A longstanding dispute about the nature of these S bands was recently settled by g-factor determinations, which showed them to have vi~3 @ rotation-aligned structure, and by the first observations 9 of key 12+~10+ low-energy transitions in Hg. Other interesting spectral features seen systematically across the even-A Hg nuclei are semidecoupled 5 bands' with dominant microscopic components of the type (vit3~q, vj). The properties of the lower-spin members of these bands are reproduced well in model calculations. " %e report here the results of a study of levels in ' Hg by the reaction '96Pt(n, 4ny). These results are much more extensive than those recently reported,~and they clarify some important aspects of the ' Hg level structure.The experiments were performed by bombarding a selfsupporting 650 pg/cm Pt foil, enriched to 97oio in '96Pt, with 48.6-MeV n-particle beams from the Michigan State University Cyclotron. The measurements included y-ray singles with a 10% Ge(Li) and a low-energy photon spectrometer, y-ray angular distributions by intensity measurements at five angles spanning the range 90' -157', half-life determinations between the cyclotron beam-bursts, and comprehensive year coincidences with two large Ge(Li) detectors. Representative yy coincidence spectra illustrating the quality of the data are shown in Fig. 1. Those y rays observed to be in coincidence with the known 426-keV 2+ 0+ and 636-keV 4+ 2+ transitions were assigned to Hg; their energies, intensities, and angular distribution coefficients are listed in Table I. The ' Hg level scheme shown in Fig. 2 is based firmly on the yy coincidence results. The positive parity levels up to 14+ and the odd-spin negative parity levels up to 11 have been established previously, ' and half-lives of 5.1, 5.1, and 3.5 ns, respectively, have been reported' 9 for the 7 10+, and 12+ levels. Our lifetime results are consistent with these values, but we could not resolve the 10+ and 12+ half-lives as cleanly as the Bonn group did in their decisive conversion electron timing measurements.However, we find no evidence for the proposeds" 278-keV 10+ 9 2000-223 kev 1000-2000-478 keV looo-LJJ