Laser spectroscopy of the B[17.7]8-X8 and C[19.3]9-X8 transitions of holmium monochloride

Several new transitions of holmium monochloride (HoCl) have been studied at high resolution using laser excitation spectroscopy. Two main transitions, B[17.7]8-X8 and C[19.3]9-X8 have been observed and five bands, 0-0, 0-1, 1-0, 1-1, and 2-1 of the B-X transition and three bands, 0-0, 0-1, and 0-3 of the C-X transition have been obtained at high resolution and rotationally analyzed. Among several low lying states observed in dispersed fluorescence was a strong transition from the C state to a state ∼2140 cm⁻¹ above the ground state. Excitation spectra of this transition have shown that there are apparently two states, ∼6 cm⁻¹ apart. Comparison with ligand field theory calculations are consistent with assigning these states to the excited low lying Ho⁺(4f¹¹6s)Cl⁻ configuration. Several other low lying electronic states have been observed in dispersed fluorescence spectra. Although their assignments could not be established, their energies suggest that they are from the Ho⁺(4f¹⁰6s²)Cl⁻ or Ho⁺(4f¹¹6s)Cl⁻ configurations. Rotational constants have been obtained for the B[17.7]8 and C[19.3]9 states and have been used to speculate on the possible electron configurations for these states.     

Laser spectroscopy of the A[16.4]8.5-X7.5, A[16.4]8.5-Y[0.15]8.5, and A[16.4]8.5-Z[0.85]7.5 transitions of dysprosium monochloride

Laser-induced fluorescence spectra have been obtained at low resolution using a laser ablation source and pulsed dye laser, and at high resolution using a Broida oven and cw ring dye laser. Dispersed fluorescence spectra from two different excited states, A[16.4]8.5 and B[15.4]Ω (unknown Ω) (the states are labelled [10⁻³T₀]Ω according to their energy and Ω assignment) showed transitions to the same four low lying electronic states, X7.5, Y[0.15]8.5, Z[0.85]7.5, and an unassigned state at 970 cm⁻¹. High resolution excitation spectra of the A-X 0-0, A-Y 0-0 and 0-1, and A-Z 0-0 and 0-1 transitions were obtained and a global fit to all the data yielded rotational constants for both ¹⁶²Dy³⁵Cl and ¹⁶⁴Dy³⁵Cl. From the band origins, vibrational frequencies of 291 and 284 cm⁻¹ were obtained for the Y[0.15]8.5 and Z[0.85]7.5 states, respectively, suggesting that these two states originate from the Dy⁺(4f¹⁰6s)Cl⁻ configuration. The ¹⁶²Dy-¹⁶⁴Dy and ³⁵Cl-³⁷Cl isotope effects were studied and both indicated a ground state, X7.5, vibrational frequency of ∼230 cm⁻¹ which was reinforced by the observation, in dispersed fluorescence from the B[15.4] state, of a weak transition to a state 233 cm⁻¹ above the ground state. The observed electronic states and their configurational origin are discussed in terms of ligand field theory predictions.     

Spectroscopic Investigation of the Electronic Structure of YN: The XΣ Ground State and the New B1, C1 and D1 Excited Electronic States

YN molecules were produced in a free jet molecular beam apparatus by a laser vaporizing yttrium metal in the presence of He doped with NH₃. Laser excitation spectra were observed in the range 18 250-19 850 cm⁻¹. The ground state was confirmed to have ¹Σ⁺ symmetry. The fundamental vibration in the ground state was measured to be 650.6(1) cm⁻¹. Three new electronic states, B1, C1, and D1, were observed at 18 974.7(1), 19 023.3(1), and 19 824.0(1) cm⁻¹, respectively. The fundamental vibrations and equilibrium internuclear distances were found to be 718.3(1) cm⁻¹ and 1.939(8) for the B1 state and 723.5(1) cm⁻¹ and 1.9194(3) for the C1 state. Two additional electronic states were identified with the help of a deperturbation procedure, one of which is either the ¹Σ⁺ or the ³Σ₀⁻ state. The newly observed electronic states cannot be accounted for based on the existing ab initio results. We expect that these states correlate with the excited asymptote Y(4d¹5s²²D)+N(²D).     

Description of spin reorientation transition in Au/Co/Au sandwich with Co film thickness within a simple phenomenological model of ferromagnetic film

Simple phenomenological model of ferromagnetic film characterized by equal energies of surface anisotropies at two sides of a film (symmetric film) is considered. The model is used to describe a two-step spin reorientation transition (SRT) in Au/Co/Au sandwich with Co film thickness: the SRT from perpendicular to canted noncollinear (CNC) state at N_⊥=6.3 atomic layers and the subsequent SRT from CNC to in-plane state at _N∥=10.05$N_{\parallel }=10.05$ atomic layers. Analytic expressions for the stability criterion of collinear perpendicular and in-plane states of a film are derived with account of discrete location of atomic layers. The dependence of borders that separate regions corresponding to various magnetic states of a film in the (k_B,k_S)-diagram on film thickness N is established. k_S(k_B) is surface (bulk) reduced anisotropy constant. The comparison of theory with experiment related to Au/Co/Au sandwich shows that there is a whole region in the (k_B,k_S)-diagram corresponding to experimentally determined values of threshold film thicknesses N_⊥=6.3 and _N∥=10.05$N_{\parallel }=10.05$. The comparison of this region with similar region determined earlier for a bare Co/Au film within the same model of asymmetric film and characterized by N_⊥=3.5, _N∥=5.5$N_{\parallel }=5.5$ shows that the intersection of these regions is not empty. Hence, both the SRT in Au/Co/Au sandwich and in bare Co/Au film with Co film thickness can be described within the same model using the same magnitudes of model parameters k_S, k_B. Based on this result we conclude that the energy of Neel surface anisotropy at free Co surface is negligible compared to the energy of Co–Au interface anisotropy. It is demonstrated that the destabilization of collinear states in symmetric film leads to occurrence of the ground CNC state and two novel metastable CNC states. These three CNC states exhibit different kinds of symmetry. In case of asymmetric film only ground CNC state occurs on destabilization of collinear states of a film.     

Ab initio potential energy curves and vibrational levels for the c, l, and i states of the hydrogen molecule

Potential energy curves for the hydrogen molecule in the c³Π_u, I¹Π_g, and i³Π_g state have been calculated in the Born-Oppenheimer approximation. Highly flexible wavefunctions have been used, and for each state the calculations have been carried out for 40 different internuclear distances in the region 1 ≤ R ≤ 12 a.u. For the Π_g states the wavefunctions are known to change their character around R = 5 a.u. The effect of this change on various components of the energy has been analyzed. The vibrational Schrödinger equation for all states has been solved for H₂, HD, and D₂. For H₂ the resulting energies are compared with the experimental values and it is shown that the adiabatic effects are likely to be responsible for the existing discrepancy between the theoretical and experimental values.     

Laser spectroscopy of holmium monosulphide: Electronic, vibrational and rotational structure of the A[14.79]8.5-X8.5, A[14.79]8.5-W[0.25]7.5 and A[14.79]8.5-V[0.98]7.5 transitions

Laser induced fluorescence spectra of HoS have been obtained using a Broida oven and a ring dye laser. Dispersed fluorescence spectra showed transitions from a common upper state, A[14.79]8.5 to the v = 0 and 1 vibrational levels of three low lying states, labelled X8.5, W[0.25]7.5 and V[0.98]7.5 (the states are labelled [10⁻³T₀]Ω according to their energy and Ω assignment). High resolution excitation spectra were obtained for all six transitions and a rotational analysis yielded the following principal constants, in cm⁻¹, for the X, W and V states, respectively: T₀ = 0, 251.8713(31), 980.6969(37); B_e = 0.121903(42), 0.121729(37), 0.122561(34); ΔG_1/2 = 463.8811(46), 462.9411(45), 461.2084(127). For the A state, T₀ = 14794.6987(28) cm⁻¹ and B₀ = 0.112596(29) cm⁻¹. The three low lying states are shown to arise from the Ho²⁺[4f¹⁰(⁵I₈)6s]S²⁻ configuration in accord with Ligand Field Theory predictions. The atomic origin of each of the three low lying electronic states was determined from the observed resolved hyperfine structure.     

Lifetime Measurements of the DΠ State of HfS and the bΠ1 State of HfO

Lifetime measurements of individual rotational levels in excited states of hafnium oxide and hafnium sulfide have been performed using population probing by resonant two-photon ionization in a molecular beam. For the b³Π₁ state of HfO rotational levels in the vibrational level v=0 were found to have lifetimes in the region 650-700 ns. For the D¹Π state of HfS rotational level lifetimes in the vibrational levels v=0 and v=1 were determined to be around 240 ns. The technique used here provides very accurate results and the uncertainty in the reported values is only about 2%. Possible sources of errors are examined. The absorption oscillator strengths from the ground state are calculated.     

Bound states in N = 8 supergravity and N = 4 supersymmetric Yang-Mills theories

We present a study of possible bound states in N = 8 supergravity. We find evidence for the existence of multiplets of two-body bound states and expect that many-body bound states may exist as well. Our study is based on a calculation of Regge trajectories in the two-body scattering amplitudes of the lagrangian field theory. We also study Regge trajectories in N = 4 Yang-Mills theory and find evidence for a possible spin zero, SU(4) and gauge singlet, massless bound state. If such a state actually exists and supersymmetry is not broken, it may be a member of a supersymmetric multiplet which includes the graviton.     

Fourier transform emission spectroscopy and ab initio calculations on WO

Emission spectra of WO have been observed in the 4000-35 000 cm⁻¹ region using a Fourier transform spectrometer. Molecules were produced by exciting a mixture of WCl₆ vapor and He in a microwave discharge lamp. A ³Σ⁻ state has been assigned as the ground state of WO based on a rotational analysis of the observed bands and ab initio calculations. After rotational analysis, a majority of strong bands have been classified into three groups. Most of the transitions belonging to the first group have an Ω = 0⁺ state as the lower state while the bands in the second group have an Ω′′ = 1 state as the lower state. These two lower states have been assigned as X0⁺ and X1 spin components of the X³Σ⁻ ground state of WO. The third group consists of additional bands interconnected by common vibrational levels involving some very low-lying states. The spectroscopic properties of the low-lying electronic states have been predicted from ab initio calculations. The details of the rotational analysis are presented and an attempt has been made to explain the experimental observations in the light of the ab initio results.     

Nonadiabatic effects in the B, C, B′, and D states of H2

The Kolos-Wolniewicz potentials for the H₂$\text{B}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and C¹Π_u states were used together with the hypothesis of pure precession for the rotation-electronic interaction, to calculate the nonadiabatic energy levels of these states for J = 1 to 5. The complete coupling matrix was computed using accurate numerical vibrational wavefunctions. The calculated Λ-doubling of the v = 0 to 12 C vibrational levels generally agrees well with experimental values, and the nonadiabatic shifts in the B rotational constants qualitatively explain the difference between the theoretical and RKR potentials for this state.The interaction of the B′${}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ and D¹Π_u states was also investigated, but only qualitatively since adiabatic potentials of sufficient accuracy do not exist for these states. The Λ-doubling of the Dv = 0 rotational levels agrees well with the experimental values. An appreciable “background” nonadiabatic shift in the B′ rotational constants was found. This shift, which is nearly 5 percent of B_v, is in addition to that of strong local two-level interactions and was not “deperturbed” in constructing the B′ RKR potential. The result is that the RKR turning points differ by about 0.04 au from the “true” adiabatic turning points. This conclusion is supported by a Hartree-Fock calculation of the B′ potential to the left of R_e.     

Coherent states and global entanglement in an N qubit system

We consider an N qubit system and show that in the symmetric subspace, S, a pure state is not globally entangled, iff it is a coherent state. It is also proven that in the orthogonal complement S_⊥ all states are globally entangled.     

Barrier D centers in a quantum disc

The bound states of the barrier D⁻ center, which consists of a positive ion located on the z-axis at a distance λ from the two-dimensional quantum disc plane with a confined parabolic potential and two electrons in the disc plane bound by the ion, are studied under a perpendicular homogeneous magnetic field. The binding energies of the three lowest bound states are calculated as a function of the applied magnetic field strength γ. Discontinuous ground state transitions induced by an external magnetic field have been obtained. We have investigated the effect of the impurity position and found that the transition of the ground-state occurs for finite λ with increasing γ.     

Transition rates of autoionizing 3s3p6up (n=4,5,6) states of argon

Transition rates for autoionizing …3s3p⁶np (n = 4,5,6) states of argon are presented using simple analytical functions for the bound states and the Coulomb function for the continuum state. The results are in very good agreement with experiment.     

Quantum state transfer via a two-qubit Heisenberg XXZ spin model

Transfer of quantum states through a two-qubit Heisenberg XXZ spin model with a nonuniform magnetic field b is investigated by means of quantum theory. The influences of b, the spin exchange coupling J and the effective transfer time T=Jt on the fidelity have been studied for some different initial states. Results show that fidelity of the transferred state is determined not only by J, T and b but also by the initial state of this quantum system. Ideal information transfer can be realized for some kinds of initial states. We also found that the interactions of the z-component Jz and uniform magnetic field B do not have any contribution to the fidelity. These results may be useful for quantum information processing.     

Vibronic structure of the 3s Rydberg state of the 2-methylallyl radical

Resonance-enhanced multiphoton ionization combined with electronic ground state depletion spectroscopy of jet-cooled 2-methylallyl (C₄H₇) radicals provides vibronic spectra of the 3s and 3p Rydberg states. Analysis of the vibronic structure following one-photon and two-photon excitation of rovibronically cold 2-methylallyl radicals and its isotopologues C₄H₄D₃ and C₄D₇ reveals transitions to more than 30 vibrational levels in the 3s Rydberg state that are identified and reassigned on the basis of predictions from ab initio calculations and results from pulsed-field-ionization zero-kinetic-energy photoelectron spectra obtained with resonant multiphoton excitation via selected intermediate states. Depletion spectroscopy reveals transitions to short-lived 3p Rydberg states that have a large oscillator strength.     

Properties of pp annihilations into strange particles at 702 and 757 MeV/c

$\text{p}\text{p}$ annihilations, leading to the production of at least one neutral K meson in the final state, have been studied in the incident momentum region of 700–760 MeV/c. Topological cross sections and cross sections for the various exclusive final states are presented. Detailed analyses of the different final states have been carried out to study the importance of resonance production and of quasi two-body and quasi three-body processes. A detailed study of the $\text{K}\text{K}\text{π}$ system in the four-body final states shows that the F₁ meson is a spurious effect due to systematic biases. In the momentum range investigated, the C = +1 final states are strongly suppressed.     

The 14N quadrupole coupling constants and barrier to internal rotation of ethylcyanide-d5

The microwave spectrum of ethylcyanide-d₅ has been recorded from 18.0 to 40.0 GHz. Both a-type and b-type transitions were observed and assigned. Also, the R-branch assignments have been made for three excited states of the internal torsional mode and two excited states of the CN inplane bending mode as well as an excited vibrational state involving both of these motions. The barrier to internal rotation was determined to be 3.00 ± 0.15 kcal/mole from the E, A splittings of the third excited state. The quadrupole coupling constants of the¹⁴N nucleus were found to have values of ?3.213, 1.168, and 2.045 MHz for χ_aa, χ_bb, and χ_cc, respectively. These results are compared to those previously obtained on the corresponding hydrogen compound.     

Exact excitation spectrum of the Zn + 1 × Zn + 1 generalized Heisenberg model

We describe the excitations of the generalization of the Heisenberg anisotropic hamiltonian to Z_{n + 1} spins. We analyse the Bethe ansatz equations without assuming the existence of strings. Excited states above an antiferromagnetic ground state are described by a finite number of parameters, which verify system of equations. We give the energy and momentum of the excitations. In a suitable limit we recover the spectrum of a relativistically invariant theory.     

Laser spectroscopy of the B[21.68]8-X8, B′[21.65]8-X8 and C[22.3]7-X27 transitions of holmium monofluoride

The spectrum of holmium monofluoride (HoF) in the blue (420-480 nm) region has been studied using laser-induced fluorescence. Previous work [J. Phys. B 7 (1974) L234] had assigned several bands in this region to the B8-X8 transition. By obtaining wavelength selected laser excitation spectra at high resolution and rotationally analyzing seven bands in this region, we have shown that not all the bands previously assigned to the B8-X8 system belong to the same electronic transition and have identified three separate transitions which we have labelled B8-X8, B′8-X8, and C7-X₂7. Preliminary low resolution dispersed fluorescence spectra have shown several excited states at energies greater than 4000 cm⁻¹ above the ground state and, though not all could be assigned, ligand field theory calculations are consistent with assigning them to the first excited spin-orbit component of the Ho⁺(4f¹⁰6s²)F⁻ ground state configuration or to the first excited configuration, Ho⁺(4f¹¹6s)F⁻. The results of the dispersed fluorescence experiments also tentatively place the X₂7 state at ∼70 cm⁻¹ above the ground X7 state.