A theoretical study of rotational-vibrational levels of the lower two 2Σ+ states of the CaH molecule

Computation of the rotational vibrational levels of the X²Σ⁺ and B²Σ⁺ states of the CaH molecule is carried out by using the adiabatic potential curves obtained by an ab initio SCF-CI calculation (N. Honjou, M. Takagi, M. Makita, and K. Ohno, J. Phys. Soc. Japan 50, 2095–2100 (1981)). Due to two minima in the adiabatic potential curve of the B²Σ⁺ state, an irregularity is found in the rotational-vibrational levels.     

Determination of the Rydberg D and F° energy levels of Cs-like ions by the method of interpolation of relativistic quantum defects

Data are presented that allow one to determine the energy values of the Rydberg levels nD _3/2, nD _5/2, nF _5/2°, and nF _7/2° for ions of the cesium isoelectronic sequence by the method of interpolation of rela- tivistic quantum defects in the Dirac-Fock approximation. To improve agreement with the experimental data, it is proposed to use an empirical correction for the quantum defect. The obtained energy values are compared with the experimental data. The anomalous behavior of the quantum defects of the nf levels is discussed. The calculations are carried out for ten ions of the cesium isoelectronic sequence.     

High resolution IR spectrum of the ν8 band of CH2DF: analysis of the interactions with the near vibrational levels

The IR spectrum of the ν₈ band of monodeutero methyl fluoride has been recorded with a resolution of 0.004 cm^?1 using a Fourier transform spectrometer. The ν₈ vibration, of A′′ symmetry species, gives rise to a pure c-type envelope centred at 1298.58 cm^?1, resembling a perpendicular band of a prolate symmetric rotor. From the spectral analysis it has been found that ν₈ is coupled with ν₄ for the low K_a sublevels while for the higher ones other vibrational states, directly or indirectly, are also interacting. For satisfactory reproduction of the rovibrational data of ν₈, the Watson's Hamiltonian in the I^r representation has been implemented with interaction parameters, which included first- and second-order a-, b-type and c-type Coriolis couplings with ν₄ and ν₉, respectively. Being these states also interacting with other levels, the effective spectroscopic parameters of the analysed band up to fourth order have been obtained from a data set formed by the six fundamentals located below 1500 cm^?1.     

Energy levels of the Fröhlich polaron in a spherical quantum dot

The one-phonon variational state is suitably applied to describe the ground state and excited states of the Fröhlich polaron bound to a quantum dot. A general analytical expression for the electronic energy spectra and the polaron binding energy for different electronic subband bound states in a quantum dot is presented and discussed with reference to the parameters of a real solid.     

Energy levels of λx 2k anharmonic oscillators using the quantum normal form

The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the HamiltonianH=–d ²/dx ²+x ²+x ^2k (k=3, 4,...) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.     

Deep levels of intrinsic point defects and the nature of “anomalous” optical absorption in ZnGeP2

Deep levels of single vacancies and antisite defects in the structure of the ZnGeP₂ compound are investigated using the pseudopotential method and an extended unit cell. The data obtained are compared with those for the GaP isoelectronic analog. It is demonstrated that, in the case of the ZnGeP₂ crystal, deep levels (degenerate in the GaP structure) are substantially split as a result of lowering the lattice symmetry and anisotropy of the chemical bonding. In particular, the splitting of the V _P ⁰ (t ₂) level is equal to 1.58 eV. The averaged levels of defects in the ZnGeP₂ compound are in close agreement with the levels of defects in the GaP compound. The absorption coefficients for polarized light are calculated with allowance made for the neutral and charged states of the defects. The optical transitions responsible for the absorption peaks in the IR range of the spectrum of the ZnGeP₂ compound are revealed. It is shown that the first peaks are associated with the transitions of electrons from the valence band states located deep in the Brillouin zone to the V _Zn ^?1 and V _P ⁰ deep levels. This leads to a considerable shift (by ～0.3 eV) of these peaks toward the high-energy range as compared to the energy positions of the deep levels in the band gap with respect to the top of the valence band. The experimental data on the photoinduced EPR spectra of postgrowth and electron-irradiated ZnGeP₂ crystals are consistently interpreted by analyzing the electron density.     

Studying parity-nonconservation effect in the conversion transition between the levels of the (5/2)± doublet in the 229Pa nucleus

Effects of weak nucleon interaction are calculated for the ground-state doublet of 5/2^± levels of the strongly deformed nucleus ²²⁹Pa₉₁. A parity-nonconservation effect in the doublet states can be observed in the conversion spectrum for the isomeric transition between the doublet levels. By using a generalized model of the nucleus, the matrix element of the effective one-nucleon weak-interaction potential, which determines the weight of the opposite parity admixture in the doublet components is estimated in the single-particle approximation. The reduced probabilities of the E1 and M1 nuclear transitions between the doublet states are calculated within various models of the deformed nuclear potential. The effect of Coriolis forces on the dipole electric transition in question is considered. The lifetime of the upper doublet state is estimated.     

On the possibility of studying crystal field levels and excitations by μ+SR spectroscopy

We point out that ⁺SR relaxation timesT ₁ andT ₂ measured in metallic magnetic materials can sometimes be expressed in terms of the spin-spin correlation functions of the magnetic ions. We calculate these functions in a random phase approximation and notice they can strongly depend on the crystal field levels and excitations of the magnetic ions. The shortcomings of this approximation are discussed.Part of this work was done at the French Atomic Commission at Grenoble.     

Polarization phenomena upon excitation by the Λ-scheme and at an anisotropic population of lower levels

We have investigated the possibility of the formation of dark states and of the change in the sign of the alignment of an ensemble of atoms with the filled ns-shell the state (n + 1)³ S ₁ of which is excited by the Λ-scheme from states n ³ P ₁ and n ³ P ₂, which, in turn, are populated by means of an axially symmetric interaction.     

Charge transfer transitions and location of the rare earth ion energy levels in Ca-α-SiAlON

The broad bands in the room-temperature excitation spectra of Sm³⁺-, Dy³⁺- and Tm³⁺-activated Ca-α-SiAlON phosphors are interpreted as the N³⁻-to-rare earth charge transfer transition (CTT). From the energies of the charge transfer transitions and from the optical data presented for the Eu²⁺ ion, the location of the divalent rare earth ion energy levels relative to the valence and the conduction band of Ca-α-SiAlON is derived. The salient features of the energy-level diagram are shown to be practical in explaining the temperature-dependent variations of the Eu²⁺ and Yb²⁺ luminescence efficiency in Ca-α-SiAlON. A comparative study pertaining to the nature of the Yb²⁺ and Eu²⁺ ion luminescence in Ca-α-SiAlON and in SrSi₂O₂N₂ is presented. A tentative energy-level diagram of the trivalent rare earth ions in Ca-α-SiAlON is also constructed.     

Calibrated binding energies of some core levels in the energy range between 1.5–4 keV

A commercial photoelectron spectrometer equipped with four interchangeable anodes (Mg, Al, Ag, Ti) has been utilized after careful calibration for accurately measuring binding energies of several deep core levels in the energy range between 1.5–4 keV.     

Study of the levels in 174Lu by (p, 3nγ) spectroscopy

The nuclear levels in ¹⁷⁴Lu were investigated by means of ¹⁷⁶Yb(p, 3nγ) reaction spectroscopy. Standard germanium detector techniques as well as an on-line curved crystal spectrometer were used. Six well-developed rotational bands are observed. These results confirm and extend the scheme previously obtained by direct reactions. The presented data document a study on the anomalous g-factors of the 142 d isomeric band.     

Excitonic influences on the anticrossing gap of Wannier–Stark levels in a wide well superlattice

In this paper we compare different theoretical calculations with experimental data of anticrossings of a wide well semiconductor superlattice in the Wannier–Stark regime. Calculations have been performed by using a variation method and a numerical method. For the variation method we used different approaches to minimize energy. With the numerical model, continuum states were calculated and anticrossing of 1s states with continuum states were found. Calculations have been performed for h1e1(0)–h1e2( − 1) and h1e1(1)–h1e2(0) anticrossings and are compared with data from photocurrent experiments.     

Rotation–torsion analysis of the Si2H6 infrared fundamental ν9, perturbed by excited torsional levels of the vibrational ground state

The lowest infrared active perpendicular fundamental ν₉ of disilane has been analysed on a Fourier transform spectrum between 320 and 430?cm^?1, at the spectral resolution of 0.0012?cm^?1. The rotation–torsion structure of this band is affected by x,y Coriolis interactions with excited torsional levels of the vibrational ground state, correlating with components of 3ν₄ and 4ν₄ in the high barrier limit. The interaction of ν₉ and 4ν₄, forbidden in the D_3d symmetry limit, is allowed between components of E torsional symmetry under the G₃₆(EM) extended molecular group, because of the large amplitude of the internal rotation motion. We could determine the values of the main vibration–rotation–torsion parameters of ν₉, interaction parameters, and the vibrational wavenumbers of the four torsional components of 3ν₄ and of the E_3d component of 4ν₄. The intrinsic torsional splitting of ν₉ is found to be smaller than in the ground vibrational state by 0.0066?cm^?1, in good agreement with our theoretical predictions. The possibility of observing the effects of D_3d-forbidden interactions in the spectra of ethane-like molecules is also discussed.     

Lifetimes of rovibrational levels of the long-range I′ 1Πg state of H2 and D2: experiment and theory

The lifetimes of the lowest lying rovibrational levels of the outer well I′ ¹Π_g state of molecular hydrogen were measured for both H₂ and D₂. The measurements were made by direct observation of the time-dependent decay of the fluorescence. The observed lifetimes depend on isotopomer and increase with vibrational excitation. The predominant decay route for these levels is fluorescence. Previously published ab initio lifetimes calculated for these states, which accounted for non-adiabatic interactions [J. Chem. Phys. 92, 7461 (1990)], are in good agreement with experiment for H₂ but are too long by four or five orders of magnitude for D₂. We present new ab initio results at the adiabatic level for the fluorescence lifetimes. The current results are in reasonable agreement with the experimental lifetimes for both H₂ and D₂. We explain the isotopomer and vibrational dependence of the lifetimes and discuss the neglected interactions and decay pathways.     

High-resolution rovibrational analysis of vibrational states of A2 symmetry of the dideuterated methane CH2D2: the levels ν 5 and ν 7 + ν 9

The infrared spectrum of the CH₂D₂ molecule has been measured in the region 900–1500?cm^?1 on a Bomem DA002 Fourier transform spectrometer with a resolution of 0.0024?cm^?1 (FWHM, unapodized). Transitions belonging to the hot bands ν ₇?+?ν₉?ν ₇, ν₇?+?ν₉? ν ₉, ν₅?+?ν₇?ν₅, and ν₅?+?ν₉?ν₅ were extracted from the recorded spectra to determine the rovibrational energies of the A₂ symmetry vibrational states (v ₇?=?v ₉?=?1) at 2329.698?cm^?1 and (v ₅ ?=?1) at 1331.409?cm^?1. Vibrational energies as well as rotational and centrifugal distortion parameters of the (v ₇?=?v ₉=1) and (v ₅?=?1) states were determined that reproduce the experimental rovibrational energy levels of the (v ₇?=?v ₉?=?1) and (v ₅?=?1) vibrational states with a d _rms deviation of 0.0017 and 0.0006?cm^?1, respectively. The results are discussed in relation to the equilibrium structure of methane, which is redetermined here from the experimental data, and in relation to its potential hypersurface and anharmonic vibrational dynamics.     

Theoretical calculation of energy levels and radiative lifetimes of T1 I

Considering the perturbation,the results of theoretical calculation of five Rydberg series energy levels 6s~2ns~2S_(1/2)(n=7-20),6s~2nd~2D_(3/2)(n=6-20),6~s2nd~2D_(5/2)(n=6-20),6s~2np~2p_(1/2)~0(n=7-20),and 6s~2np~2p_(3/2)~0(n=7-20)for T11 are presented using the weakest bound electron potential model(WBEPM) theory.Furthermore,the radiative lifetimes of this five series are also calculated.The calculated values of energy levels and lifetimes are in good agreement with the experimental results.