Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Bond formation (2)
- Dissociation energies (2)
- Electron-electron interactions (2)
- Electron-phonon interactions. (2)
- Fourier transform infrared spectroscopy (2)
-
- High resoultion spectroscopy (2)
- Hydrogen bonding (2)
- Molecular dynamics (2)
- Rotation constants (2)
- SF (2)
- Superfluorescence (2)
- 3P (1)
- Breit formula (1)
- Calcium (1)
- Collisional coupling (1)
- Collisional resdistribution (1)
- Data analysis (1)
- Electron excitation (1)
- Energy transfer (1)
- Erratum (1)
- Exchange interaction (1)
- Excited states (1)
- Excited-state alignment-to-orientation (1)
- External magnetic field (1)
- Frequency analyzers (1)
- Ground states (1)
- Molecualar spectroscopy (1)
- Molecular spectroscopy (1)
- Molecular vibrational analysis (1)
- Na (1)
Articles 1 - 15 of 15
Full-Text Articles in Physics
Phase Diagram Of The One-Dimensional Hubbard-Holstein Model At Half And Quarter Filling, Rahul Hardikar, R. T. Clay
Phase Diagram Of The One-Dimensional Hubbard-Holstein Model At Half And Quarter Filling, Rahul Hardikar, R. T. Clay
Scholarship and Professional Work - LAS
The Hubbard-Holstein model is one of the simplest to incorporate both electron-electron and electron-phonon interactions. In one dimension at half filling, the Holstein electron-phonon coupling promotes on-site pairs of electrons and a Peierls charge-density wave, while the Hubbard on-site Coulomb repulsion U promotes antiferromagnetic correlations and a Mott insulating state. Recent numerical studies have found a possible third intermediate phase between Peierls and Mott states. From direct calculations of charge and spin susceptibilities, we show that (i) as the electron-phonon coupling is increased, first a spin gap opens, followed by the Peierls transition. Between these two transitions, the metallic intermediate …
Temperature-Driven Transition From The Wigner Crystal To The Bond-Charge-Density Wave In The Quasi-One-Dimensional Quarter-Filled Band, R. T. Clay, Rahul Hardikar, S. Mazumdar
Temperature-Driven Transition From The Wigner Crystal To The Bond-Charge-Density Wave In The Quasi-One-Dimensional Quarter-Filled Band, R. T. Clay, Rahul Hardikar, S. Mazumdar
Scholarship and Professional Work - LAS
It is known that within the interacting electron model Hamiltonian for the one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal only if the nearest-neighbor electron-electron repulsion is larger than a critical value. We show that this critical nearest-neighbor Coulomb interaction is different for each spin subspace, with the critical value decreasing with increasing spin. As a consequence, with the lowering of temperature, there can occur a transition from a Wigner crystal charge-ordered state to a spin-Peierls state that is a bond-charge-density wave with charge occupancies different from the Wigner crystal. This transition is possible because spin excitations …
Intermediate Phase Of The One Dimensional Half-Filled Hubbard-Holstein Model, R. T. Clay, Rahul Hardikar
Intermediate Phase Of The One Dimensional Half-Filled Hubbard-Holstein Model, R. T. Clay, Rahul Hardikar
Scholarship and Professional Work - LAS
We present a numerical study of the Hubbard-Holstein model in one dimension at half filling, including finite-frequency quantum phonons. At half filling, the effects of the electron-phonon and electron-electron interactions compete with the Holstein phonon coupling acting as an effective negative Hubbard on-site interaction U that promotes on-site electron pairs and a Peierls charge-density wave state. Most previous work on this model has assumed that only Peierls or Mott phases are possible at half filling. However, there has been speculation that a third metallic phase exists between the Peierls and Mott phases. We confirm the intermediate phase, and show that …
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Superfluorescence Polarization: Signature Of Collisional Redistribution, A. Kumarakrishnan, S. Chudasama, Xianming Han
Scholarship and Professional Work - LAS
We have studied effects of magnetic sublevel degeneracy on the polarization of superfluorescent pulses generated on the Ca 4s4p1P1–3d4s1D2 transition at 5.5μm. These pulses were generated from a cell of length 50 cm by optically pumping calcium vapor on the 4s21S0–4s4p1P1 transition in the presence of Ar gas. The axis of ellipticity of superfluorescence (SF) polarization is oriented parallel to the axis of the pump-laser polarization at large detunings, and undergoes an abrupt rotation through 90° for detunings close to resonance. The distribution of populations in the magnetic sublevels of the 1P1 state can be estimated using a simple model …
Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han
Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han
Scholarship and Professional Work - LAS
We have studied superfluorescence (SF) under highly unfavorable conditions of rapid collisional and radiative distribution in a Doppler-broadened medium. Nanosecond SF pulses at 5.5 μm were generated on the Ca 4s4p1P1–3d4s1D2 transition from a column of calcium vapor buffered with Ar by optically pumping the 4s21S0–4s4p1P1 transition. The Rabi frequency associated with the intense pump pulse prevents the occurrence of SF while the pump laser is on. As a result, the predicted scaling laws that describe the properties of SF in a transversely excited system, such as peak heights, pulse widths, and delay times, are shown to apply in our …
Magnetic-Field-Induced Alignment-To-Orientation Conversion In Sodium, G. W. Schinn, Xianming Han
Magnetic-Field-Induced Alignment-To-Orientation Conversion In Sodium, G. W. Schinn, Xianming Han
Scholarship and Professional Work - LAS
We report a detailed investigation of excited-state alignment-to-orientation conversion in the presence of an external magnetic field. This counterintuitive phenomenon occurs under intermediate-coupling conditions. A weak, linearly polarized, cw laser beam was used to excite and align the Na 3P3/2 state in an atomic beam along the z direction. The degree of circular polarization of the resulting fluorescence was detected along the z direction as a function of magnetic-field strength. The spectrally integrated transitions originating from individual F levels of the 3S1/2 state yield a maximum circular-polarization fraction of ∼40%; integrating the circular polarization over all the allowed 3S1/2-3P3/2 transitions …
Fine‐Structure Mixing Within The Zn(43pj) Multiplet By Collisions With The Noble Gases, Xianming Han, J. F. Kelly
Fine‐Structure Mixing Within The Zn(43pj) Multiplet By Collisions With The Noble Gases, Xianming Han, J. F. Kelly
Scholarship and Professional Work - LAS
Measurements of rate coefficients for intramultiplet state transfer of Zn(4 3 P 1→4 3 P J’) by collisions with the rare gases are presented. The state‐to‐state binary rate coefficients are derived from least‐squares fittings of the time‐resolved triexponential behavior of the 4 3 P 1fluorescence. These rate coefficients were studied systematically over a temperature range of 690–1100 K in order to characterize the velocity dependence of the collisional coupling. The systematic behavior of the rate coefficients with varying temperature and noble gas species is qualitatively consistent with a nearly adiabatic coupling limit for noncrossing levels.
Differential, Partial Cross Sections For Electron Excitation Of The Sodium 3p State, Xianming Han, G. W. Schwinn, A. Gallagher
Differential, Partial Cross Sections For Electron Excitation Of The Sodium 3p State, Xianming Han, G. W. Schwinn, A. Gallagher
Scholarship and Professional Work - LAS
Using a powerful laser-based experimental method, the cross section for electron excitation of Na(3S) atoms to the Na(3P) state has been decomposed into partial components with respect to changes in the spin and angular momentum of the atomic electron, and these partial cross sections are further reduced to their differential character with respect to the electron scattering angle. Partial, differential cross sections are reported for electron collision energies from threshold 2.1 to 3.6 eV, and compared to available calculations.
Spin-Exchange Cross Section For Electron Excitation Of Na 3s 3p Determined By A Novel Spectroscopic Technique, Xianming Han, G. W. Schwinn, A. Gallagher
Spin-Exchange Cross Section For Electron Excitation Of Na 3s 3p Determined By A Novel Spectroscopic Technique, Xianming Han, G. W. Schwinn, A. Gallagher
Scholarship and Professional Work - LAS
An experimental technique is described which enables determination of the partial cross sections for electron excitation of atoms as a function of changes in spin and orbital angular momentum. This method provides a good signal-to-noise ratio in the energy region near threshold, and could be used to study long- or short-lived excited states of many atomic systems. Measurements for Na 3S−3P, near-threshold excitation are reported here. The results are generally in good agreement with the close-coupling calculations of D. L. Moores and D. W. Norcross [J. Phys. B 5, 1482 (1972)] for the largest ΔmS and ΔmL components of …
Erratum: Determination Of Dissociation Energies And Thermal Functions Of Hydrogen Bond Formation Using High Resolution Ftir Spectroscopy [J. Chem. Phys. 8 7, 5674 (1987)], B. A. Wofford, M. E. Eliades, Shannon Lieb, J. W. Bevan
Erratum: Determination Of Dissociation Energies And Thermal Functions Of Hydrogen Bond Formation Using High Resolution Ftir Spectroscopy [J. Chem. Phys. 8 7, 5674 (1987)], B. A. Wofford, M. E. Eliades, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
Erratum
The Spectroscopy And Molecular Dynamics Of The High Frequency Ν1 6 Intermolecular Vibrations In Hcn‐‐‐Hf And Dcn‐‐‐Df, B. A. Wofford, M. W. Jackson, Shannon Lieb, J. W. Bevan
The Spectroscopy And Molecular Dynamics Of The High Frequency Ν1 6 Intermolecular Vibrations In Hcn‐‐‐Hf And Dcn‐‐‐Df, B. A. Wofford, M. W. Jackson, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν0 6 [ν0=1132.4783(2) cm− 1] in HCN‐‐‐HF and its corresponding perdeuterated fundamental ν1 6 [ν0=409.1660(2) cm− 1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K 6 6=537(17) and K 6 6 6 6=4.98(12) cm− 1 which in turn are used to estimate the pertinent cubic band stretching interaction constants …
Molecular Dynamics In Hydrogen‐Bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field For Hcn‐‐‐Hf, B. A. Wofford, Shannon Lieb, J. W. Bevan
Molecular Dynamics In Hydrogen‐Bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field For Hcn‐‐‐Hf, B. A. Wofford, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
Observation of the 2ν1 overtone band in the hydrogen‐bonded complex HCN‐‐‐HF permits evaluation of the anharmonicity constant X 1 1=−116.9(1) cm− 1 and determination of the anharmonicity corrected fundamental frequency ω1. This information, and available data from previous rovibrational analyses in the common and perdeuterated isotopic species of HCN‐‐‐HF, offer an opportunity for calculation of an approximate stretching harmonic force field. With the assumptions f 1 2=f 2 4=0.0, the remaining force constants (in mdyn/Å) are evaluated as: f 1 1=8.600(20), f 2 2=6.228(9), f 3 3=19.115(40), f 4 …
Determination Of Dissociation Energies And Thermal Functions Of Hydrogen‐Bond Formation Using High Resolution Ftir Spectroscopy, B. A. Wofford, M. E. Eliades, Shannon Lieb, J. W. Bevan
Determination Of Dissociation Energies And Thermal Functions Of Hydrogen‐Bond Formation Using High Resolution Ftir Spectroscopy, B. A. Wofford, M. E. Eliades, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bonddissociation energiesD 0 and D e . Results for HCN‐‐HF give a D 0=20.77(22) and D e =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and a b i n i t i o molecular orbital calculations. Rovibrational band information available for HCN‐‐HF also permits evaluation of thermal functions of dimer formation in kJ/mol: ΔU ○ 298.2 =20.1(2), ΔH ○ 298.2 =22.6(2), ΔG ○ 298.2 =59.4(2), ΔS ○ 298.2 =−0.1235.
Preliminary Rovibrational Analysis Of The Nν6+Ν1−Nν6 Vibration In Hcn⋅⋅⋅Hf, E. Kyrö, K. Mcmillan, M. Eliades, D. Danzeiser, P. Shoja-Chaghervand, Shannon Lieb, J. W. Bevan
Preliminary Rovibrational Analysis Of The Nν6+Ν1−Nν6 Vibration In Hcn⋅⋅⋅Hf, E. Kyrö, K. Mcmillan, M. Eliades, D. Danzeiser, P. Shoja-Chaghervand, Shannon Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
A preliminary rotation‐vibration analysis of the n=0 and n=1 subbands associated with the nν6+ν1−nν6 hydrogen‐bonded vibration in HCN⋅⋅⋅HF has been completed. The following excited staterotational constantsB′ and band origin frequencies ν0 have been determined for the complex. The results are consistent with a rotation‐vibration interaction constant α1=−68.3±1 MHz which correlates with an excited stater(N⋅⋅⋅F) internuclear distance of 2.762 Å, a decrease of 0.034 Å relative to the ground state.Excited state lifetimes associated with assigned transitions are demonstrated to be …
Travelling-Wave Sub-Doppler Excited Molecule Energy Transfer Spectroscopy, Khalid Iqbal, Shannon G. Lieb, J. W. Bevan
Travelling-Wave Sub-Doppler Excited Molecule Energy Transfer Spectroscopy, Khalid Iqbal, Shannon G. Lieb, J. W. Bevan
Scholarship and Professional Work - LAS
A general formulation of traveling‐wave sub‐Doppler excited molecule energy transferspectroscopy is presented. The line profile analysis is applied to that determined experimentally for the R(22) ν3 HCN transition. Pn the noise equivalent power of the detector is demonstrated to be ⩽10−12 W. Finally, the technique is applied to resolve the KsR(7) ν1 transition head in NH3.