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(207)Pb Spin-Lattice Relaxation In Solid Pbmoo(4) And Pbcl(2), Peter A. Beckmann, Shi Bai, Alexander J. Vega, Cecil Dybowski
(207)Pb Spin-Lattice Relaxation In Solid Pbmoo(4) And Pbcl(2), Peter A. Beckmann, Shi Bai, Alexander J. Vega, Cecil Dybowski
Physics Faculty Research and Scholarship
We have measured the (207)Pb nuclear spin-lattice relaxation rate R as a function of temperature T at two nuclear magnetic resonance frequencies omega(0) in the ionic solids lead molybdate (PbMoO(4)) and lead chloride (PbCl(2)). R is unexpectedly large, proportional to T(2), and independent of omega(0). Taken together with previous work in lead nitrate [Pb(NO(3))(2)], these results show that the relaxation does not depend on the nature or rotational motion of the counterion, particularly since the counterion in lead chloride is a single chlorine atom. The theory that explains the observed relaxation rate is reviewed. A second-order Raman process dominates the …
Spin-Lattice Relaxation Of Heavy Spin-1/2 Nuclei In Diamagnetic Solids: A Raman Process Mediated By Spin-Rotation Interaction, Alexander J. Vega, Peter A. Beckmann, Shi Bai, Cecil Dybowski
Spin-Lattice Relaxation Of Heavy Spin-1/2 Nuclei In Diamagnetic Solids: A Raman Process Mediated By Spin-Rotation Interaction, Alexander J. Vega, Peter A. Beckmann, Shi Bai, Cecil Dybowski
Physics Faculty Research and Scholarship
We present a theory for the nuclear spin-lattice relaxation of heavy spin-1/2 nuclei in solids, which explains within an order of magnitude the unexpectedly effective lead and thallium nuclear spin-lattice relaxation rates observed in the ionic solids lead molybdate, lead chloride, lead nitrate, thallium nitrate, thallium nitrite, and thallium perchlorate. The observed rates are proportional to the square of the temperature and are independent of magnetic field. This rules out all known mechanisms usually employed to model nuclear spin relaxation in lighter spin-1/2 nuclei. The relaxation is caused by a Raman process involving the interactions between nuclear spins and lattice …
Many-Body Interactions In A Sample Of Ultracold Rydberg Atoms With Varying Dimensions And Densities, Thomas J. Carroll, Shubha Sunder, Michael Noel
Many-Body Interactions In A Sample Of Ultracold Rydberg Atoms With Varying Dimensions And Densities, Thomas J. Carroll, Shubha Sunder, Michael Noel
Physics Faculty Research and Scholarship
Ultracold highly excited atoms in a magneto-optical trap (MOT) are strongly coupled by the dipole-dipole interaction. We have investigated the importance of many-body effects by controlling the dimensionality and density of the excited sample. We excited three different cylindrical volumes of atoms in the MOT to Rydberg states. At small radius, where the sample is nearly one-dimensional, many-body interactions are suppressed. At larger radii, the sample becomes three-dimensional and many-body effects are apparent.
Double Resonance Spectroscopy Of The B″B̅ 1Σu+ State Of H2, R. C. Ekey, A. Marks, Elizabeth Mccormack
Double Resonance Spectroscopy Of The B″B̅ 1Σu+ State Of H2, R. C. Ekey, A. Marks, Elizabeth Mccormack
Physics Faculty Research and Scholarship
Double resonance spectroscopy via the EF (1)Sigma(+)(g),nu'(EF)=6,J(') state has been used to probe the rovibrational structure of the ungerade double-well B-n(B) over bar (1)Sigma(+)(u) state of H-2. Transitions to the B-n(B) over bar (1)Sigma(+)(u),nu((B) over bar)=17-35,J=0-4 levels of the outer-well and to the nu(n)(B)((B) over bar)=46-50,J=0-4 levels of the combined inner and outer wells above the barrier have been recorded by detecting both molecular and atomic ion production as a function of energy by using a time of flight mass spectrometer. Theoretical energy calculations incorporating the most recent potential curves have been used to aid in the assignment of observed …
Magnetic Properties Of One-Dimensional Quasiperiodic Co/Pt Multilayers, L. Y. Zhu, Xuemei Cheng, C. L. Chien
Magnetic Properties Of One-Dimensional Quasiperiodic Co/Pt Multilayers, L. Y. Zhu, Xuemei Cheng, C. L. Chien
Physics Faculty Research and Scholarship
We have fabricated Fibonacci [Co/Pt] multilayers with two constituent Co/Pt bilayers, as well as periodic multilayers of the same Co/Pt bilayers, all of which exhibit perpendicular magnetic anisotropy. Magnetic properties of the quasiperiodic and periodic [Co/Pt] multilayers have been studied macroscopically by vibrating sample magnetometry and microscopically by magnetic force microscopy. The Fibonacci [CoPt] multilayers show enhanced squareness in magnetic hysteresis loops compared to the corresponding periodic [Co/Pt]n multilayers, due to a smaller density of isolated nucleation sites in the saturation state.
Unusual Magnetization Reversal In [Co/Pt]4 Multilayers With Perpendicular Anisotropy, Xuemei Cheng, V. I. Nikitenko, A. J. Shapiro, R. D. Shull, C. L. Chien
Unusual Magnetization Reversal In [Co/Pt]4 Multilayers With Perpendicular Anisotropy, Xuemei Cheng, V. I. Nikitenko, A. J. Shapiro, R. D. Shull, C. L. Chien
Physics Faculty Research and Scholarship
Unusual magnetization reversal of [Co(4 Å)/Pt(10 Å)]4 multilayers with perpendicular magnetic anisotropy has been revealed macroscopically by magnetometry measurements and microscopically by magneto-optical Kerr effect microscopy and magnetic force microscopy (MFM) imaging. During the first-order reversal process, the magnetization first decreases, then reaches a plateau, and finally rises back to saturation, corresponding to expanding bubble domains, stationary domains, and fading contrast but unchanged boundary domains, respectively. MFM imaging reveals the existence of many submicron-scaled unreversed channels within the boundary of the “bubble” domains. The magnetization reversal behavior can be accounted for by the evolution of the unusual domain structures …
Cf3 Rotation In 3-(Trifluoromethyl)Phenanthrene. X-Ray Diffraction And Ab Initio Electronic Structure Calculations, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Peter A. Beckmann, Arnold L. Rheingold, Michelle M. Francl
Cf3 Rotation In 3-(Trifluoromethyl)Phenanthrene. X-Ray Diffraction And Ab Initio Electronic Structure Calculations, Xianlong Wang, Frank B. Mallory, Clelia W. Mallory, Peter A. Beckmann, Arnold L. Rheingold, Michelle M. Francl
Physics Faculty Research and Scholarship
The molecular and crystal structure of 3-(trifluoromethyl)phenanthrene has been determined by X-ray diffraction. The structure of the isolated molecule has been calculated using electronic structure methods at the HF/3-21G, HF/6-31G*, MP2/6-31G* and B3LYP/6-31G* levels. The potential energy surfaces for the rotation of the CF3 group in both the isolated molecule and cluster models for the crystal were computed using electronic structure methods. The barrier height for CF3 rotation in the isolated molecule was calculated to be 0.40 kcal mol-1 at B3LYP/6-311+G**//B3LYP/6-311+G**. The B3LYP/6-31G* calculated CF3 rotational barrier in a 13-molecule cluster based on the X-ray data was found to be …