Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (A 1 Σ + ) and the first excited (A 1 Σ + ) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs + , Li + and Na + cores, parameterized l -dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the A + Σ + state using the Franck–Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the A + Σ + state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice.
Calculations of the adiabatic potential energy curves and the transition dipole moments between the ground (A 1 Σ + ) and the first excited (A 1 Σ + ) states have been determined for the LiCs and NaCs molecules. The calculations are performed using an ab initio approach based on non-empirical pseudopotentials for Cs + , Li + and Na + cores, parameterized l -dependent polarization potentials and full configuration interaction calculations. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the A + Σ + state using the Franck–Condon (FC) approximation and the approximate sum rule method. The radiative lifetimes associated with the A + Σ + state are presented here for the first time. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice.
The adiabatic potential energy curves and the spectroscopic constants of the ground and the first excited states of LiK+, LiRb+ and LiCs+ ionic molecules have been performed. The transition dipole moment between the ground (X2Σ+) and the first excited (22Σ+) state have been determined for each ionic molecule. We have used an ab initio approach involving non‐empirical pseudo‐potentials with core valence effects taken into account through parameterized l‐dependent polarization potentials. Our spectroscopic constants of the ground and the first excited states are in good agreement with the available theoretical works. The potential energy curves and the transition dipole moment are used to estimate the radiative lifetimes of the vibrational levels of the 22Σ+ state for the first time. In addition to the bound‐bound contribution, the bound‐free term has been evaluated exactly and using the Franck‐Condon (FC) approximation and added to the total radiative lifetime. These data can help experimentalists to optimize photoassociative formation of ultracold molecules and their longevity in a trap or in an optical lattice.
In this thesis properties of ultracold alkali dimers are studied both theoretically and experimentally. In the first, theoretical, part, the prospects for the formation of ultracold LiCs dimers in deeply bound vibrational levels using photoassociation (PA) are investigated. Furthermore a previous systematic investigation of the structure of all alkali dimers is extended by the ab initio calculation of static dipole polarizabilities. An extensive comparison with other published results supports the reliability of the chosen method. Based on these results an experimental scheme for the creation of an sample of oriented ultracold dipolar molecules is developed. In the second, experimental part the formation of LiCs ground state molecules by PA is investigated. PA spectroscopy is used to improve the accuracy of the potential energy curve for the B1P and the value of the dissociation energy of the X1S+ state significantly. The rovibrational distribution of ground state molecules is probed in a combination of resonance-enhanced multi-photon ionization and depletion spectroscopy. A simple scheme is found to form ultracold polar LiCs molecules in the absolute ground state X1S+,v''=0,J''=0. In a quasi-electrostatic trap created by a CO2 laser, LiCs molecules are formed and stored. A lifetime of 24(3)s, limited by collisions with background gas, is observed and rate coefficients for inelastic collisions between LiCs in high vibrational states and Cs atoms are determined. The long storage time facilitates the observation of radiative decay of polar molecules towards lower vibrational levels.
We apply the relativistic configuration-interaction valence-bond method to calculate various characteristics of the alkali-metal RbCs dimer. These include the electronic potentials and transition dipole moments between the ground and first excited states and permanent dipole moments of the X 1sigma+ and a 3sigma+ states of the ground configuration. In addition, we estimate the lifetime of the rovibrational levels of the X state due to blackbody radiation. These data can help experimentalists to optimize photoassociative formation of ultracold RbCs molecules and their longevity in a trap or in an optical lattice. Extended basis sets, constructed from Dirac-Fock and Sturm's orbitals, have been used to ensure convergence of our calculations. We compare our data with other theoretical and experimental results when they were available.
Obtaining effective spontaneous radiative transition channels is a fundamental topic in the preparation of ultracold rovibrational ground states of molecules. Herein, the ranges of prospective transition channels in the NaCs dimer are predicted via exploring the complex energy level structure and transition properties. The potential energy curves of \ensuremath{\Lambda}-S states and \ensuremath{\Omega} states, spectroscopy constants, absolute energies of bound states, and transition information (Frank-Condon factors, lifetimes, transition dipole moments) have been researched. With this purpose, the results of our experiment on binding energies of the ${b}^{3}{\mathrm{\ensuremath{\Pi}}}_{0}{}^{+}$ rovibrational states are analyzed; the transition from the higher (photoassociated) ${}^{1}\mathrm{\ensuremath{\Pi}}$ state to the ground ${X}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ state is discussed. The wavelengths of the two lasers are predicted as 622.8-656.7 nm and 896.3-969.8 nm with the ${B}^{1}{\mathrm{\ensuremath{\Pi}}}_{1}$ and ${c}^{3}{\mathrm{\ensuremath{\Sigma}}}_{1}^{+}$ states, respectively, for the stimulated raman adiabatic passage method.
Using a potential energy curve (based primarily on the RKR potential of Amiot and Verges [J. Chem. Phys. 112, 7068 (2000)]) and a dipole moment function (based primarily on ab initio calculations of Park et al. [Chem. Phys. 257, 135 (2000)]), we have calculated radiative transition probabilities (Einstein A coefficients), radiative lifetimes, and dipole moment expectation values involving all vibrational levels (for several rotational quantum numbers) of the X1Sigma+ ground state of 39K85Rb. We observe that the radiative lifetimes of vibrationally excited levels, in particular, are approximately 10(3)-10(6) seconds, far too long to be significant in most ultracold experiments involving 39K85Rb or its isotopomers. Comparison with other molecules (LiH and HF) suggests that simple scaling (A approximately mu2nu3 approximately tau(-1)) will predict similarly long lifetimes for many other heteronuclear molecules, e.g., RbCs.
Abstract Alkaline-earth and alkali-metal mixtures have an electronic structure that is perfect for laser cooling. This makes them highly attractive for trapping and laser cooling experiments, allowing the formation of cold molecules. For this object, potential-energy curves and relevant spectroscopic parameters of the low-lying electronic excited states of 1,3Σ+, 1,3Π, and 1,3Δ symmetries of molecular-ion systems composed of alkaline-earth-ion and Francium alkali-metal-atom: ALKE-Fr+ (ALKE = Be, Mg, Ca and Sr), are determined using advanced theoretical technique in quantum chemistry, including a non-empirical pseudopotential, core-valence correlation, large Gaussian basis sets and Full Configuration Interaction (FCI). In order to obtain a more accurate understanding of the electronic structure of these systems, we also determined transition and permanent dipole moments and vibrational properties. Thereafter, the spontaneous and the black-body stimulated transition rates were determined and were employed to calculate lifetimes for all vibrational states of the ground electronic states 11Σ+ of molecular-ions under consideration. For the first and the second excited states, radiative lifetimes were investigated via the Franck–Condon approximation including bound-bound and bound-free transitions. High diagonal structure and large Franck Condon Factor (FCF) values f 00 = 0.987, f 11 = 0.959 and f 22 = 0.919 were obtained for the 11Π (v′ = 0, 1, 2)→ 11Σ+ (v = 0, 1, 2) transition making the BeFr+ system a good candidate for laser cooling. Furthermore, the current results could be used to investigate elastic scattering properties in cold-ion-atom collisions for the first excited states and may help the experimentalists for possible formation, spectroscopy, and photoassociation of cold ion-atom mixtures.