Coherent interaction and action-counteraction theory in small polaron systems,and ground state properties

Based on the coherent interaction and action-counteraction principles, we investigate the ground state properties for small polaron systems, the coherent-squeezed fluctuation correction, and the anomalous lattice quantum fluctuation, with the new variational generator containing correlated squeezed-coherent coupling and quantum entanglement. Noting that $-2t $ is the T.B.A. energy, for the coherent interaction effect, we find the ground-state energy $E_0$ to be $-2.428t$, in which the coherent squeezed fluctuation correction $-A_0 t$ is $-0.463t $ (where $ t $ is the hopping integral, $\omega $ is the phonon frequency), with the electron-one-phonon coupling constant $g=$1 and the electron-two-phonon coupling constant $g_{1}=-0.1$. However, as a result of the action-counteraction effect, $\tilde{{E}}_{0} $ is $-2.788t$, but $-\tilde{{A}}_{0} t$ is $-0.735t$. As to the polaron binding energy $(E_{\rm P} )$, for the coherent interaction effect, $E_{\rm P} $ is $-1.38\omega $, but for the action-counteraction effect, $\tilde{{E}}_{\rm P}$ is $-1.88\omega $. In particular, the electron-two-phonon interaction noticeably enlarges the coherent interaction and the coherent squeezed quantum fluctuation correction. By intervening with the quantum entanglement, the evolutions of the squeezed coherent state and the lattice quantum fluctuation begin to take control. At that time, we encounter a new quantum phase coherence phenomenon — the collapse and revival of inversion repeatedly for the coherent state in the entangled evolution.     

The far-infrared laser magnetic resonance spectrum of the CF radical and determination of ground state parameters

Observations in the far-infrared laser magnetic resonance spectrum of the CF radical in its ground ²Π state have been extended to include fine structure transitions between the two spin components. The data are fitted together with all previous measurements relating to the v = 0 level to obtain a complete set of molecular parameters, including the spin-orbit splitting which has been determined at 77.196916(14) cm⁻¹. The implications for the electronic structure of various parameters are also discussed.     

Magnetic excitations in systems with a nonmagnetic ground state and valence fluctuations

The neutron inelastic scattering data for the spectra of f-electron excitations in valence-unstable semiconductors SmB₆, SmS, and YbB₁₂ are discussed. The conclusions on the relation of the spectral characteristics to the nature of exciton-type states formed in these systems are reported.     

The rotational spectrum of HC8N, a linear molecule with a triplet ground state

By means of Fourier transform microwave spectroscopy of a supersonic molecular beam, we report here the laboratory detection of HC₈N, a carbon chain with a triplet electronic ground state. A total of 71 hyperfine components from six rotational transitions between 8 and 13 GHz were measured to an uncertainty of 5 kHz or better. Eight spectroscopic constants, including six fine and hyperfine coupling constants, were determined to high accuracy, despite a complex spectrum which consists of many closely spaced lines. Like the shorter HC_2nN chains, the linear triplet isomer detected here is highly polar and is almost certainly the ground state of HC₈N; in our molecular beam discharge source, it is 10 times less abundant than triplet HC₆N, but more than 100 times less abundant than the well-studied closed-shell cyanopolyyne HC₇N. Owing to the collapse of the hyperfine structure with increasing chain length, still longer chains may be detectable.     

The ground state torsion-rotation spectrum of propargyl alcohol (HCCCH2OH)

The rotation-torsion spectrum of the asymmetric frame-asymmetric top internal rotor propargyl alcohol (HCCCH₂OH) has been extended into the millimeter and submillimeter wave spectral regions. Over 2000 ground torsional state transitions have been measured and analyzed up to rotational quantum numbers J = 80 and K_a = 33 through a frequency of 633 GHz. The newly measured transitions were added to approximately 200 previously reported and now unambiguously assigned microwave transitions to comprise a data set of 2390 transitions which has been fit to 59 kHz using a reduced axis method (RAM) Hamiltonian. The ground state has been confirmed to consist of a symmetric and an antisymmetric gauche conformer with no spectroscopic evidence of stable trans conformer. A complete set of rotation and distortion constants through 6th order and a number of the 8th and one 10th order constants for the normal species are presented along with those determined from a re-analysis of the existing OD species data. The a and b symmetry Coriolis interaction constants and the gauche+ gauche− tunnelling frequency of 652389.4 MHz has been determined for the OH species while the b symmetry Coriolis interaction and the 213 480 MHz tunnelling frequency were determined for the OD species.     

Determination of electronic ground state properties of a dinuclear iron(II) spin crossover complex

The dinuclear complex [(Fe(L-N₄Me₂))₂(BiBzIm)](ClO₄)₂?2EtCN (1) has been investigated by Mössbauer spectroscopy carried out in the temperature range from 5 to 150 K with externally applied magnetic fields of up to B = 5 T. By means of a consistent simulation of all experimental data sets within the Spin Hamiltonian formalism, the zero-field splitting D and the rhombicity parameter E/D of the ferrous high-spin (HS) site in this complex was determined to be D = ?15.0 ± 1.0 cm^?1 and E/D = 0.33 respectively. The sign of the quadrupole splitting of the HS site is positive which indicates that this iron site of the dinuclear complex 1 has an electronic ground state with the d_xy orbital being twofold occupied.     

Probing the ground state properties of iron-based superconducting pnictides and related systems by muon-spin spectroscopy

In this short review, we attempt to give a comprehensive discussion of studies performed to date by muon-spin spectroscopy (more precisely the relaxation and rotation technique, also know as μSR) on the recently discovered layered iron-based superconductors. On one side, μSR has been used to characterize the magnetic state of different families of layered iron-based systems. Similarly the subtle interplay of the magnetic state and the structural transition present in some families has been investigated. We will also discuss the information provided by this technique on the interaction between the magnetic state and the superconducting phase. Finally the μSR technique has been used to investigate the magnetic penetration depth of the superconducting ground state. The study of its absolute value, temperature and magnetic field dependence provides crucial tests for investigating possible unconventional superconducting states in such systems.     

Electronic properties of quasi-one-dimensional compounds with a charge/spin-density wave ground state

First, a review of the general properties of the collective transport induced by the charge (CDW)/spin (SDW) density wave motion in quasi-one-dimensional conductors is presented. Then the three recent developments in this field are emphasized, namely: high spatial resolution x-ray study of the field-induced CDW deformations; quantum interference effects in magnetotransport of a sliding CDW through columnar defects; manifestation of disorder in the CDW/SDW ground state in thermodynamic properties at very low temperatures. Fiz. Tverd. Tela (St. Petersburg) 41, 759–763 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

The microwave spectrum,harmonic force field,and ground state average structure of 1,1-dichloroethylene

The microwave spectra of several isotopic species of 1,1-dichloroethylene have been measured up to high J values and have been analyzed for rotational constants and quartic centrifugal distortion constants. An approximate harmonic force field for the molecule has been obtained by combining the centrifugal distortion constants with known vibrational data. The harmonic force field has been used together with the results of the present and other microwave studies to determine the ground state average molecular structure.     

The forbidden (J → J + 1) spectrum of CH4 in the ground vibronic state

The pure rotational R-branch spectrum of CH₄ arising from the centrifugal distortion moment has been studied using a simple 12.10-m light-pipe cell and a conventional interferometer. Ten forbidden (J → J + 1) transitions for J = 7 to J = 16 have been observed in the spectral region 80–200 cm^?1 with a theoretical resolution of 0.5 cm^?1. The integrated intensity of the six strongest lines has been measured and was found to be of the order of twice that calculated from the distortion moment obtained earlier from a molecular beam study of the (J = 2) rotational level. In the approximation that frequency shifts due to this excess intensity are neglible, it has been determined that the rotational constant B₀ = (5.245 ± 0.004) cm^?1 and the scalar distortion constant D_S = (1.19 ± 0.09) × 10^?4 cm^?1. It is argued that the excess intensity is due to higher-order terms in the dipole moment operator and the validity of the frequency analysis is considered in this context.     

Excited state properties of 5H-dibenzo(a,d) cycloheptene

A number of photophysical properties of 5H-dibenzo(a,d) cycloheptene have been measured including the emission and triplet-triplet absorption spectra. The quantum yields and decay parameters for the triplet state of this molecule as a function of temperature have also been measured. The results are discussed and compared to those of molecules.     

Selection rules and Raman spectrum of a molecule with a degenerate ground state and zero spin-orbit coupling: VCl4

Two interesting features can normally be expected in the Raman spectrum of a molecule with a degenerate electronic ground state (i) the contribution of asymmetric or even antisymmetric tensors to the Raman intensity (ii) lifting of the electronic degeneracy due to Jahn-Teller distortion. The experimental data and discussion on VCl₄, presented here, show that this molecule does not show any deviations in the Raman selection rules. Further, its Raman spectrum closely resembles that of TiCl₄ which also has T_d geometry but a nondegenerate singlet ground state. This suggests the absence of any static Jahn-Teller distortion in VCl₄. However, we have observed a broadening of the ν₂ band of VCl₄ over TiCl₄ and we attribute this to a possible dynamic Jahn-Teller splitting.