Electronic spectroscopy and excited state mixing of OThF.

Electronic spectra for OThF have been recorded using fluorescence excitation and two-photon resonantly enhanced ionization techniques. Multiple vibronic bands were observed in the 340-460 nm range. Dispersed fluorescence spectra provided ground state vibrational constants and evidence of extensive vibronic state mixing at higher excitation energies.

Photoelectron Velocity Map Imaging Spectroscopy of the Beryllium Trimer and Tetramer.

Computational studies of small beryllium clusters (Be) predict dramatic, nonmonotonic changes in the bonding mechanisms and per-atom cohesion energies with increasing . To date, experimental tests of these quantum chemistry models are lacking for all but the Be molecule. In the present study, we report spectroscopic data for Be and Be obtained via anion photodetachment spectroscopy.

High resolution electronic spectroscopy of uranium mononitride, UN.

The isoelectronic molecules UN and UO+ are known to have Ω = 3.5 and Ω = 4.5 ground states, respectively (where Ω is the unsigned projection of the electronic angular momentum along the internuclear axis).

Kinetics of O with Ca and Its Higher Oxides CaO ( = 1-3) and Updates to a Model of Meteoric Calcium in the Mesosphere and Lower Thermosphere.

The room-temperature rate constants and product branching fractions of CaO ( = 0-3) + O are measured using a selected ion flow tube apparatus. Ca + O produces CaO + O with = 9 ± 4 × 10 cm s, within uncertainty equal to the Langevin capture rate constant. This value is significantly larger than several literature values.

Near-thermo-neutral electron recombination of titanium oxide ions.

While the dissociative recombination (DR) of ground-state molecular ions with low-energy free electrons is generally known to be exothermic, it has been predicted to be endothermic for a class of transition-metal oxide ions. To understand this unusual case, the electron recombination of titanium oxide ions (TiO) with electrons has been experimentally investigated using the Cryogenic Storage Ring. In its low radiation field, the TiO ions relax internally to low rotational excitation (≲100 K).

Electronic Spectroscopy of Jet-Cooled NdO.

Chemi-ionization reactions of the type M + O → MO + (M = Nd or Sm) are currently being investigated as a method to artificially increase the electron density in the ionosphere for control of micro- and radio wave propagation. Experiments involving the release of atomic Nd into the upper atmosphere have resulted in the production of a cloud that, on excitation by solar radiation, emits green light. It has been assumed that NdO was the carrier of this emission, but the existing spectroscopic data needed for this attribution is lacking.

Kinetics of Metastable Argon Optical Excitation and Gain in Ar/He Microplasmas.

The optically pumped rare-gas metastable laser is capable of high-intensity lasing on a broad range of near-infrared transitions for excited-state rare gas atoms (Ar*, Kr*, Ne*, Xe*) diluted in flowing He. The lasing action is generated by photoexcitation of the metastable atom to an upper state, followed by collisional energy transfer with He to a neighboring state and lasing back to the metastable state. The metastables are generated in a high-efficiency electric discharge at pressures of ∼0.

Electronic Configuration Assignments for UO from Electric Dipole Moment Measurements.

Diatomic UO has more than 48 bound states within 10000 cm of the ground state. This electronic state congestion has been attributed to interleaved states from the electronic configurations U(57)O and U(57)O, respectively. Ligand field theory predicts that each electronic configuration will exhibit states with distinguishable, characteristic vibrational and rotational constants.

Electronic Spectroscopy of SmO in the 645 to 670 nm Range.

The associative ionization reaction Sm + O → SmO + is being investigated as an electron source that could transiently modify high-altitude electron densities via Sm vapor release. Electronic spectra have been obtained from tests where sounding rockets released Sm vapor, but the interpretation of these results has been hampered by the limited laboratory spectral data available for both SmO and SmO. The present study extends the spectroscopic characterization of SmO in the 645-670 nm range, where the field data show the most prominent molecular emission features.

Gas-Phase Reactivity of Ozone with Lanthanide Ions (Sm, Nd) and Their Higher Oxides.

The kinetics of SmO ( = 0-2) and NdO ( = 0-2) with O are measured using a selected-ion flow tube. Reaction of Nd to yield NdO + O occurs rapidly, with a rate constant near the capture-controlled limit of ∼8 × 10 cm s. NdO reacts at ∼40% of the capture limit to yield NdO with little temperature dependence from 200 to 400 K.

Electronic Spectroscopy and Photoionization of LiBe.

LiBe has been the subject of several theoretical investigations and one spectroscopic study. Initially, these efforts were motivated by interest in the intermetallic bond. More recent work has explored the potential for producing LiBe and LiBe at ultracold temperatures.

Electronic Spectroscopy and Photoionization of LiMg.

Dimers consisting of an alkali metal bound to an alkaline earth metal are of interest from the perspectives of their bonding characteristics and their potential for being laser cooled to ultracold temperatures. There have been experimental and theoretical studies of many of these species, but spectroscopic data for LiMg and the LiMg cation are sparse. In this study, rotationally resolved electronic spectra for LiMg are presented.

Dipole-phonon quantum logic with alkaline-earth monoxide and monosulfide cations.

Dipole-phonon quantum logic (DPQL) leverages the interaction between polar molecular ions and the motional modes of a trapped-ion Coulomb crystal to provide a potentially scalable route to quantum information science. Here, we study a class of candidate molecular ions for DPQL, the cationic alkaline-earth monoxides and monosulfides, which possess suitable structure for DPQL and can be produced in existing atomic ion experiments with little additional complexity. We present calculations of DPQL operations for one of these molecules, CaO, and discuss progress towards experimental realization.

Spectroscopy and electronic structure of the hypermetallic oxide, MgOMg.

Electronic spectra for the hypermetallic oxide MgOMg have been observed in the 21 100 cm-24 000 cm spectral range using laser induced fluorescence and two-photon resonantly enhanced ionization techniques. Rotationally resolved data confirmed the prediction of a X̃Σ ground state. The spectrum was highly congested due to the optical activity of a low-frequency bending mode and the presence of three isotopologues with significant natural abundances.

Computational investigation of energy transfer and line broadening for Ar + He collisions.

Potential energy curves for all states arising from the interaction of He with the 3p, 3p4s, and 3p4p configurations of Ar have been determined using high-level electronic structure calculations. The results have been used to examine collisional energy transfer probabilities and spectral line shape parameters (shifting and broadening rate coefficients). The main focus has been on states and transitions that are of relevance to optically pumped He/Ar laser systems.

Characterization of the Ground States of BeC and BeC via Photoelectron Velocity Map Imaging Spectroscopy.

Due to their potentially unique properties, beryllium carbide materials have been the subject of many theoretical studies. However, experimental validation has been lacking due to the difficulties of working with Be. Neutral beryllium dicarbide has been predicted to have a T-shaped equilibrium structure (), while previous quantum chemistry calculations for the structure of the anion had not yielded consistent results.

Time-dependent simulations of a CW pumped, pulsed DC discharge Ar metastable laser system.

Optically pumped rare gas lasers have the potential for scaling to output powers above the kW level. In these devices, electrical discharges through He/Rg mixtures (Rg = Ne, Ar, Kr and Xe) are used to generate metastable Rg atoms in the 1s state. Optical pumping to the 2p level, followed by collisional relaxation to 2p, is then used to produce lasing on the 2p-1s transition.

Characterization of gas-phase thorium nitride.

Properties of gas-phase thorium nitride, ThN, have been experimentally determined from a combined optical and microwave spectroscopic study. An intense band near 555 nm has been assigned as the [18.0]1.

Low energy states of NdO probed by photoelectron spectroscopy.

The ionization energy (IE) of NdO and the low-energy electronic states of NdO have been examined by means of two-color photoionization spectroscopy. The value obtained for the IE, 5.5083(2) eV, is 0.

The electronic structure of thorium monoxide: Ligand field assignment of states in the range 0-5 eV.

Configuration interaction ligand field theory (CI LFT) calculations of the electronic energy levels of ThO were performed by treating the molecular electronic states as Th free-ion levels perturbed by the ligand field of O . Twenty nine experimentally characterized ThO v = 0 energy levels, together with the energy difference between the v = 0 levels of the Y and W states were fitted using a CI LFT model that included Th 7s , 6d7s, 6d , 7s7p, 6d7p, 5f7s, and 7p configurations. Predictions from these calculations were used to provide tentative assignments for 171 out of 250 ThO band heads listed by Gatterer et al.

Ab initio interatomic potentials and transport properties of alkali metal (M = Rb and Cs)-rare gas (Rg = He, Ne, Ar, Kr, and Xe) media.

We performed a first principle systematic calculation on the adiabatic potential energy curves (PECs) of alkali metal (M = Rb and Cs) - rare gas (Rg = He, Ne, Ar, Kr, and Xe) van der Waals molecules over a wide range of interatomic distance R. All electron basis sets of triple and quadruple zeta valence quality were used for the He, Ne, Ar and Kr atoms. Scalar relativistic effects were taken into account for the heavy Rb, Cs and Xe atoms by means of Dirac-Fock effective core potentials.

Dative Bonding between Closed-Shell Atoms: The BeF Anion.

Beryllium can exhibit unusually strong attractive interactions under conditions where it is nominally a closed-shell atom. Two prominent examples are the Be dimer and the He-BeO complex. In the present study, we examine the bonding of the closed-shell Be-F anion.

Photoelectron Velocity Map Imaging Spectroscopy of the Beryllium Sulfide Anion, BeS.

Slow electron velocity map imaging (SEVI) spectroscopy was used to examine the BeS anion to neutral ground-state transition, X Σ → X Σ. Rotational constants, vibrational intervals, and the electron binding energy of BeS were determined. Partially resolved rotational contours were seen due to the relatively small moment of inertia of beryllium sulfide.

Photodetachment spectroscopy of the beryllium oxide anion, BeO.

The XΣ→XΣ anion to neutral ground state photodetachment of BeO has been studied by means of photoelectron velocity-map imaging spectroscopy in a newly constructed apparatus. Vibrational intervals, rotational constants, and the electron detachment threshold of BeO were determined for the first time. The small moment of inertia of beryllium oxide allowed for the observation of partially resolved rotational contours.