We report ab initio correlated relativistic calculations of the effective electric field W_d acting on the electron in two excited electronic states of PbO, required for extracting the electric dipole moment of the electron from an ongoing experiment at Yale, which has the potential of improving accuracy for this elusive property by several orders of magnitude. The generalized relativistic effective core potential and relativistic coupled cluster methods are used, followed by nonvariational one-center restoration of the four-component wavefunction in the heavy atom core. W_d is -3.2\times 10^24 Hz/ecm for the a(1) state and -9.7\times 10^24 Hz/ecm for the B(1) state. Comparison of calculated and experimental values of the hyperfine constant A_{\parallel} provides an accuracy check for the calculation.
We report first configuration interaction calculations of hyperfine constants A_\parallel and the effective electric field W_d acting on the electric dipole moment of the electron, in two excited electronic states of ^{207}PbO. The obtained hyperfine constants, A_\parallel = -3826 MHz for the a(1) state and A_\parallel = 4887 MHz for the B(1) state, are in very good agreement with the experimental data, -4113 MHz and 5000 \pm 200 MHz, respectively. We find W_d = -(6.1 ^{+1.8}_{-0.6}) 10^{24} Hz/(e cm) for a(1), and W_d = (8.0 \pm 1.6) 10^{24} Hz/(e cm) for B(1). The obtained values are analyze…
Ab initio theory is developed for radiative transitions between excited states of neon. Calculations of energies for even excited states J=1, J=2 supplement our previous calculations for J=1 odd excited states. Line strengths for transitions between J=1 odd and J=1,2 even states of Ne I are evaluated. A comparison with experiments and semiempirical calculations is given.
We formulate the theory for a diatomic molecule in a spatially degenerate electronic state interacting with a non-resonant laser field and investigate its rovibrational structure in the presence of the field. We report on \textit{ab initio} calculations employing the double electron attachment intermediate Hamiltonian Fock space coupled cluster method restricted to single and double excitations for all electronic states of the Rb$_2$ molecule up to $5s+5d$ dissociation limit of about 26.000$\,$cm$^{-1}$. In order to correctly predict the spectroscopic behavior of Rb$_2$, we have also calculate…
Recently a breakthrough has been achieved in laser-spectroscopic studies of short-lived radioactive compounds with the first measurements of the radium monofluoride molecule (RaF) UV/vis spectra. We report results from high accuracy \emph{ab initio} calculations of the RaF electronic structure for ground and low-lying excited electronic states. Two different methods agree excellently with experimental excitation energies from the electronic ground state to the $^2Π_{1/2}$ and $^2Π_{3/2}$ states, but lead consistently and unambiguously to deviations from experimental-based adiabatic transition …
We propose simple analytic, non-orthogonal but selectively orthogonalizable, generalized Laguerre type atomic orbitals, providing clear physical interpretation and near equivalent accuracy with numerical multi-configuration self-consistent field, to atomic configuration interaction calculations. By analyzing the general Eckart theorem we use their simple interpretation, via a thorough investigation in orbital space, to estimate, for the first time (the exact value being, or considered, unknown), an ab-initio energy uncertainty, i.e. proximity to the exact energy, for several excited atomic sta…
We build the first analytic empirical potential for the most deeply bound $\mbox{Li}_{2}$ state: $b\left(1^{3}Π_{u}\right)$. Our potential is based on experimental energy transitions covering $v=0-34$, and very high precision theoretical long-range constants. It provides high accuracy predictions up to $v=100$ which pave the way for high-precision long-range measurements, and hopefully an eventual resolution of the age old discrepancy between experiment and theory for the $\mbox{Li}\left(2^{2}S\right)+\mbox{Li}\left(2^{2}P\right)$ $C_{3}$ value. State of the art ab initio calculations predict …
The possibility of electron attachment to the valence $^{3}Π$ state of CO is examined using an {\it ab initio} bound-state multireference configuration interaction approach. The resulting resonance has $^{4}Σ^{-}$ symmetry; the higher vibrational levels of this resonance state coincide with, or are nearly coincident with, levels of the parent $a^{3}Π$ state. Collisional relaxation to the lowest vibrational levels in hot plasma situations might yield the possibility of a long-lived CO$^-$ state.
We have studied the correlation effects in Cs and Fr arising from the interplay of the residual Coulomb interaction to all orders and the neutral weak interaction which gives rise to the parity violating electric dipole transition to first order, within the framework of the relativistic coupled-cluster theory which circumvents the constrain of explicitly summing over the intermediate states. We observe that, the contributions arising from the perturbed doubly excited states are quite significant and hence, any calculation should not be considered accurate unless it includes the perturbed doubl…
Electric quadrupole (E2) and magnetic dipole (M1) transition amplitudes among the low-lying states of quadruply ionized vanadium V$^{4+}$, important in various field of experimental and astrophysics are presented very accurately. Most of these results are reported for the first time in the literature. Relativistic coupled-cluster theory with single, double and leading triple excitations has been employed for these calculations. Estimation of different correlation effects arising through the above formalism have been highlighted by studying core and valence electrons excitations to the excited …
Experiments with cold ion-atom mixtures have recently opened the way for the production and application of ultracold molecular ions. Here, in a comparative study, we theoretically investigate ground and several excited electronic states and prospects for the formation of molecular ions composed of a calcium ion and an alkali-metal atom: CaAlk$^{+}$ (Alk=Li, Na, K, Rb, Cs). We use a quantum chemistry approach based on non-empirical pseudopotential, operatorial core-valence correlation, large Gaussian basis sets, and full configuration interaction method for valence electrons. Adiabatic potentia…
Vibrational branching ratios in the B$^2Σ^+$ -- X$^2Σ^+$ and A$^2Π$ -- X$^2Σ^+$ optical-cycling transitions of BaH molecules are investigated using measurements and {\it ab initio} calculations. The experimental values are determined using fluorescence and absorption detection. The observed branching ratios have a very sensitive dependence on the difference in the equilibrium bond length between the excited and ground state, $Δr_e$: a 1 pm (.5\%) displacement can have a 25\% effect on the branching ratios but only a 1\% effect on the lifetime. The measurements are combined with theoretical cal…
Relativistic ab initio study on the spectroscopic and radiative properties of the lowest states and modeling of the optical cycles for the LiFr molecule
We report calculation of the energy spectrum and the spectroscopic properties of the superheavy element ion: Rf^+. We use the 4-component relativistic Dirac-Coulomb Hamiltonian and the multireference configuration interaction (MRCI) model to tackle the complex electronic structure problem that combines strong relativistic effects and electron correlation. We determine the energies of the ground and the low-lying excited states of Rf+, which originate from the 7s^26d^1, 7s^16d^2, 7s^27p^1, and 7s^16d^17p^1 configurations. The results are discussed vis-à-vis the lighter homologue, Hf^+ ion. We a…
Relativistic coupled-cluster(RCC) theory has been employed to calculate the life time of the $6 ^2P_{3/2}$ state of single ionized lead($^{207}Pb$) to an accurac y of 3% and compared with the corresponding value obtained using second order r elativistic many-body perturbation theory(RMBPT). This is one of the very few ap plications of this theory to excited state properties of heavy atomic systems. C ontributions from the different electron correlation effects are given explicitl y.
Accurate intermolecular potential-energy surfaces (IPESs) for the ground and first excited states of the Sr-H$_2$ and Yb-H$_2$ complexes were calculated. After an extensive methodological study, the CCSD(T) method with the Douglas-Kroll-Hess Hamiltonian and correlation-consistent basis sets of triple-$ζ$ quality extended with 2 sets of diffuse functions and a set of midbond functions were chosen. The obtained ground-state IPESs are similar in both complexes, being relatively isotropic with two minima and two transition states (equivalent by symmetry). The global minima correspond to the collin…
Photodissociation by ultraviolet radiation is the key destruction pathway for CS in photon-dominated regions, such as diffuse clouds. However, the large uncertainties of photodissociation cross sections and rates of CS, resulting from a lack of both laboratory experiments and theoretical calculations, limit the accuracy of calculated abundances of S-bearing molecules by modern astrochemical models. Here we show a detailed \textit{ab initio} study of CS photodissociation. Accurate potential energy curves of CS electronic states were obtained by choosing an active space CAS(8,10) in MRCI+Q/aug-c…
It has recently been argued that atoms and molecules may become good targets of determining neutrino parameters still undetermined, if atomic/molecular process is enhanced by a new kind of coherence. We compute photon energy spectrum rate arising from coherent radiative neutrino pair emission processes of metastable excited states of I$_2$ and its iso-valent molecules, $|Av \rangle \rightarrow |Xv' \rangle + γ+ ν_iν_j$ and $|A'v \rangle \rightarrow |Xv' \rangle + γ+ ν_iν_j$ with $γ$ an IR photon and $ν_{i(j)}$ $i(j)-$th neutrino mass eigenstates, and show how fundamental neutrino parameters ma…
We report a new technique to determine the van der Waals coeffcients of lithium (Li) atoms based on the relativistic coupled-cluster theory. These quantities are determined using the imaginary parts of the scalar dipole and quadrupole polarizabilities, which are evaluated using the approach that we have proposed in [1]. Our procedure is fully ab initio, and avoids the sum-over-the-states method. We present the dipole and quadrupole polarizabilities of many of the low-lying excited states of Li. Also, the off-diagonal dipole and quadrupole polarizabilites between some of the low-lying states of…
State-by-state cross sections for dissociative electron attachment and electron-impact dissociation for molecular oxygen are computed using ab initio resonance curves calculated with the R-matrix method. When O2 is in its vibrational ground state, the main contribution for both processes comes from the $^2Π_u$ resonance state of $O_2^-$ but with a significant contribution from the $^4Σ$ resonant state. Vibrational excitation leads to an increased contribution from the low-lying $^2Π_{g}$ resonance, greatly increased cross sections for both processes, and the threshold moving to lower energies.…
In this work, we report results from our extensive spectroscopic study on AlF and AlCl molecules, keeping in mind potential laboratory as well as astrophysical applications. We carry out detailed electronic structure calculations in both the molecules, including obtaining the potential energy surfaces of the $X^1Σ$ ground electronic state and some of the relevant low-lying excited electronic states belonging to $Σ$ and $Π$ symmetries. This is followed by evaluating spectroscopic constants and molecular properties such as electric dipole moments and electric quadrupole moments. Throughout, we e…
Electron-impact cross sections for dissociation processes of vibrationally excited CH radical
University of Tunis El Manar（突尼斯埃尔曼纳大学）；Sukumar Sengupta Mahavidyalaya（苏库马尔森古普塔学院）；Scottish Church College（苏格兰教会学院）；Istituto per la Scienza e Tecnologia dei Plasmi, CNR（意大利国家研究委员会等离子体科学与技术研究所）；Université de Rennes（雷恩大学）
This work presents accurate ab initio determination of the hyperfine splitting for the ground state and few low-lying excited states of 113Cd+; important candidates for the frequency standard in the microwave region, using coupled-cluster theory (CC) in the relativistic framework. The calculated hyperfine splitting are well in agreement with recent experimental results. We have also carried out the lifetimes of the 5p2P1=2 and 5p2P3=2 states, which are in well agreement with recent experimental result (Moehring et al., PRA 73 023413, 2006). The roles of different electron correlation effects i…
Experiments with paramagnetic ground or metastable excited states of molecules (ThO, HfF$^+$, YbF, YbOH, BaF, PbO, etc.) provide strong constraints on electron electric dipole moment (EDM) and coupling constant $C_{SP}$ of contact semileptonic interaction. We compute new contributions to $C_{SP}$ arising from the nucleon EDMs due to combined electric and magnetic electron-nucleon interaction. This allows us to improve limits from the experiments with paramagnetic molecules on the $CP$-violating parameters, such as the proton EDM, $|d_p|< 1.1\times 10^{-23} e\cdot $cm, the QCD vacuum angle, $|\…
Based on the idea that four excited electrons arrange themselves around the nucleus in the corners of a pyramid in order to minimize their mutual repulsion, we present an analytical model of quadruply excited states. The model shows excellent comparison with ab initio results and provides a clear physical picture of the intrinsic motion of the four electrons. The model is used to predict configuration-mixing fractions and spectra of these highly correlated states.
The electric dipole polarizabilities and hyperpolarizabilities for the lithium isotopes $^6$Li and $^7$Li in the ground state $2^2S$ and the excited states $2^2P$ and $3^2D$, as well as the leading resonance and dispersion long-range coefficients for the Li($2^2S$)--Li($2^2S$) and Li($2^2S$)--Li($2^2P$) systems, are calculated nonrelativistically using variational wave functions in Hylleraas basis sets. Comparisons are made with published results, where available. We find that the value of the second hyperpolarizability of the $2^2S$ state is sensitive to the isotopic mass due to a near cancel…
Relativistic coupled-cluster (RCC) calculations have been performed to estimate the electromagnetic forbidden transition probabilities, oscillator strengths and lifetimes of many low-lying states of five times ionized molybdenum (Mo VI). Contributions from the Breit interaction up to the first order of perturbation have been examined. Our results are in good agreement with the available other reported theoretical and experimental results. A long lifetime about 4.9854 s of the first excited state, 4d $^2D_{5/2}$, has been predicted which can be a very useful criteria in the doping process of th…
We present a time-dependent density-functional method able to describe the photoelectron spectrum of atoms and molecules when excited by laser pulses. This computationally feasible scheme is based on a geometrical partitioning that efficiently gives access to photoelectron spectroscopy in time-dependent density-functional calculations. By using a geometrical approach, we provide a simple description of momentum-resolved photoe- mission including multi-photon effects. The approach is validated by comparison with results in the literature and exact calculations. Furthermore, we present numerical…
