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Full-Text Articles in Physics
H-1 Nuclear Magnetic Resonance Spin-Lattice Relaxation, C-13 Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy, Differential Scanning Calorimetry, And X-Ray Diffraction Of Two Polymorphs Of 2,6-Di-Tert-Butylnaphthalene, Peter A. Beckmann, Kendra S. Burbank, Katharine M. Clemo, Erin N. Slonaker, Kristin Averill, Cecil Dybowski, Joshua S. Figueroa, Alicia Glatfelter, Stephanie Koch, Louise M. Liable-Sands, Arnold L. Rheingold
H-1 Nuclear Magnetic Resonance Spin-Lattice Relaxation, C-13 Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy, Differential Scanning Calorimetry, And X-Ray Diffraction Of Two Polymorphs Of 2,6-Di-Tert-Butylnaphthalene, Peter A. Beckmann, Kendra S. Burbank, Katharine M. Clemo, Erin N. Slonaker, Kristin Averill, Cecil Dybowski, Joshua S. Figueroa, Alicia Glatfelter, Stephanie Koch, Louise M. Liable-Sands, Arnold L. Rheingold
Physics Faculty Research and Scholarship
Polymorphism, the presence of structurally distinct solid phases of the same chemical species, affords a unique opportunity to evaluate the structural consequences of intermolecular forces. The study of two polymorphs of 2,6-di-tert-butylnaphthalene by single-crystal x-ray diffraction, differential scanning calorimetry (DSC), C-13 magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and H-1 NMR spin-lattice relaxation provides a picture of the differences in structure and dynamics in these materials. The subtle differences in structure, observed with x-ray diffraction and chemical shifts, strikingly affect the dynamics, as reflected in the relaxation measurements. We analyze the dynamics in terms of both discrete sums and continuous …
Staircase Band Gap Si 1-XGeX/Si Photodectectors, Zhiyun Lo, Ruolian Jiang, Youdou Zheng, Lan Zang, Zhizhong Chen, Shunming Zhu, Xuemei Cheng, Xiabing Liu
Staircase Band Gap Si 1-XGeX/Si Photodectectors, Zhiyun Lo, Ruolian Jiang, Youdou Zheng, Lan Zang, Zhizhong Chen, Shunming Zhu, Xuemei Cheng, Xiabing Liu
Physics Faculty Research and Scholarship
We fabricated Si 1-xGex/Si photodetectors by using a staircase band gap Si 1-xGex/Si structure. These devices exhibit a high optical response with a peak responsive wavelength at 0.96 μm and a responsivity of 27.8 A/W at -5 V bias. Excellent electrical characteristics evidenced by good diode rectification are also demonstrated. The dark current density is 0.1 pA/μm2 at V bias, and the breakdown voltage is -27 V. The high response is explained as the result of a staircase band gap by theoretical analysis.
Classical Subharmonic Resonances In Microwave Ionization Of Lithium Rydberg Atoms, Michael W. Noel, W. M. Griffith, T. F. Gallagher
Classical Subharmonic Resonances In Microwave Ionization Of Lithium Rydberg Atoms, Michael W. Noel, W. M. Griffith, T. F. Gallagher
Physics Faculty Research and Scholarship
We have studied the ionization of lithium Rydberg atoms by pulsed microwave fields in the regime in which the microwave frequency is equal to or a subharmonic of the classical Kepler frequency of the two-body Coulomb problem. We have observed a series of resonances where the atom is relatively stable against ionization. The resonances are similar to those seen previously in hydrogen, but with significant quantitative differences. We also present measurements of the distribution of states that remain bound after the microwave interaction for initial states near one of the classical subharmonic resonances.
Spontaneous Evolution Of Rydberg Atoms Into An Ultracold Plasma, M. P. Robinson, B. Laburthe Tolra, Michael W. Noel, T. F. Gallagher, P. Pillet
Spontaneous Evolution Of Rydberg Atoms Into An Ultracold Plasma, M. P. Robinson, B. Laburthe Tolra, Michael W. Noel, T. F. Gallagher, P. Pillet
Physics Faculty Research and Scholarship
We have observed the spontaneous evolution of a dense sample of Rydberg atoms into an ultracold plasma, in spite of the fact that each of the atoms may initially be bound by up to 100 cm21. When the atoms are initially bound by 70 cm21, this evolution occurs when most of the atoms are translationally cold, ,1 mK, but a small fraction, 1%, is at room temperature. Ionizing collisions between hot and cold Rydberg atoms and blackbody photoionization produce an essentially stationary cloud of cold ions, which traps electrons produced later. The trapped electrons rapidly collisionally ionize the remaining cold …
Superlattices, Polymorphs, And Solid State Nmr Spin-Lattice Relaxation Measurements Of 2,6-Di-T-Butylnaphthalene, Arnold L. Rheingold, Joshua S. Figueroa, Cecil Dybowski, Peter A. Beckmann
Superlattices, Polymorphs, And Solid State Nmr Spin-Lattice Relaxation Measurements Of 2,6-Di-T-Butylnaphthalene, Arnold L. Rheingold, Joshua S. Figueroa, Cecil Dybowski, Peter A. Beckmann
Physics Faculty Research and Scholarship
Two polymorphs of 2,6-di-tert-butylnaphthalene, which differ by a factor of twelve in the number of crystallographically independent tert-butyl group environments, have been characterized by a synergistic combination of low-frequency 1H NMR spin–lattice relaxation rate measurements and conventional crystallographic structure determinations.