Michael Heaven

Emory University | EU · Department of Chemistry

The kinetics of SmOn+ (n = 0-2) and NdOn+ (n = 0-2) with O3 are measured using a selected-ion flow tube. Reaction of Nd+ to yield NdO+ + O2 occurs rapidly, with a rate constant near the capture-controlled limit of ∼8 × 10-10 cm3 s-1. NdO+ reacts at ∼40% of the capture limit to yield NdO2+ with little temperature dependence from 200 to 400 K. NdO2+...

The lifetime of Ba+ ions confined in a Paul trap is found, under typical conditions, to be limited by chemical reactions with residual background gas. An integrated ion-trap and time-of-flight mass spectrometer are used to analyze the reactions of the trapped Ba+ ions with three common gases in an ultrahigh vacuum system (H2, CO2, and H2O). It is f...

The lifetime of Ba$^+$ ions confined in a Paul trap is found, under typical conditions, to be limited by chemical reactions with residual background gas. An integrated ion trap and time-of-flight mass spectrometer are used to analyze the reactions of the trapped Ba$^+$ ions with three common gases in an ultrahigh vacuum system (H$_2$, CO$_2$ and H$...

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 spa...

The electronic spectrum of ThN over the range 19600 – 21200 cm⁻¹ is remarkably congested, showing at least twenty vibronic bands originating from the ground state zero-point level. Rotationally resolved spectra for eleven of these bands have been examined to probe the underlying reasons for the dense manifold of states. Dispersed fluorescence spect...

Ligand field theory (LFT) calculations of energy levels were performed for the neutral actinide monooxides (AnO) and their singly and doubly ionized cations (AnO⁺ and AnO²⁺) by treating the molecular electronic states as Anm+ free‐ion energy levels (where An ∈ Th through Lr and m = 1, 2, 3, or 4) perturbed by the electric field of O²⁻or O⁻. LFT par...

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 s...

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 s...

Electronic spectra for the hypermetallic oxide MgOMg have been observed in the 21 100 cm⁻¹–24 000 cm⁻¹ spectral range using laser induced fluorescence and two-photon resonantly enhanced ionization techniques. Rotationally resolved data confirmed the prediction of a X̃1Σg+ ground state. The spectrum was highly congested due to the optical activity o...

Optically pumped rare gas lasers (OPRGLs) have shown great potential to generate high energy laser radiation with high beam quality. As an alternative to the diode-pumped alkali vapor lasers (DPALs), they have similar working principles and characteristics, but OPRGLs have the advantage that the gain medium is chemically inert and is appropriate fo...

Laser induced fluorescence spectra for jet-cooled CaO have been used to examine the higher vibrational levels of the A'¹Π(Xσπ⁻¹) state (v=10-17) and the v=6-8 vibrational levels of the C¹Σ⁺(Bσσ ⁻¹) state. A perturbation of v=17 of the A' state was evident, caused by a spin-orbit mediated interaction with the b³Σ⁺(Ω=1)(Xσσ ⁻¹) v=14 level. Ro-vibrati...

The low-energy electronic states of UN and UN⁺ have been examined using high-level electronic structure calculations and two-color photoionization techniques. The experimental measurements provided an accurate ionization energy for UN (IE = 50 802 ± 5 cm⁻¹). Spectra for UN⁺ yielded ro-vibrational constants and established that the ground state has...

Optically pumped rare gas lasers have the potential for scaling to high-power cw systems with good beam quality. Metastable atoms of heavier rare gases that are the lasing species are produced in an electric discharge at near atmospheric pressure. The key problem for this class of lasers at present is the development of a suitable discharge system....

Potential energy curves for all states arising from the interaction of He with the 3p6, 3p54s, and 3p54p 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 coeffi...

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 (C2v), while previous quantum chemistry calcu...

In this work, we present the first demonstration of a quasi-continuous-wave diode-pumped metastable xenon laser at atmospheric pressures. Lasing in metastable noble gas species has received increased attention in the last few years as a possible high-power laser source. This demonstration shows that metastable xenon has a sufficiently broad absorpt...

Rate constants for the removal of O2(b¹Σg+) by collisions with I2 and NO have been determined over the temperature range from 300 to 750 K. Time dependent laser induced fluorescence (LIF) from the b¹Σg+ → X³Σg- transition has been recorded in the temperature range of 297–750 K. The measured temperature-dependent rate constants for quenching of O2(b...

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 1s5 state. Optical pumping to the 2p9 level, followed by collisional relaxation to 2p10, is then used to produce...

Translationally cold BaCl⁺ has been confined in ion traps and vibrationally relaxed by means of sympathetic laser cooling. Determination of the internal temperature of the ion has been hampered by the lack of spectroscopic data for bound-bound transitions. A promising action spectroscopy scheme involves excitation of the 7–0 vibrational overtone tr...

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]1.5–X²Σ⁺ (0,0) transition and recorded at high resolution in the presence of static electric and magnetic fields. The observed optical Stark shifts we...

Non-equilibrium ThO(X) that was vibrationally hot but rotationally cold was produced by pulsed laser vaporization followed by supersonic expansion. This source was ideal for spectroscopic investigations of vibrationally excited levels of both the ground and electronically excited states. Laser induced fluorescence spectroscopy has been used to char...

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 0.54 eV higher than previous estimates. This leads to the conclusion that the autoionization reaction Nd + O → NdO⁺ + e⁻ is exothermic by 1.76(10) eV. T...

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 2+ free‐ion levels perturbed by the ligand field of O2−. Twenty nine experimentally characterized ThO v = 0 energy levels, together with the energy difference between the v = 0 l...

We performed a first principle systematic calculation on the adiabatic potential energy curves (PECs) of alkali metal (M = Rb, Cs) - rare gas (Rg = He, Ne, Ar, Kr, 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....

Rate constants for the removal of O2 b1Σ_g^+ by collisions with species relevant to combustion, H2, CO, N2O, CH4, and C2H4 have been measured in the temperature range of 297–800 K. O2(b1Σ_g^+) was produced from ground-state molecular oxygen by photoexcitation pulses from a tunable dye laser and the deactivation kinetics were followed by observing t...

Beryllium can exhibit unusually strong attractive interactions under conditions where it is nominally a closed-shell atom. Two prominent examples are the Be2dimer and the He-BeO complex. In the present study, we examine the bonding of the closed-shell Be-F-anion. This molecule preserves the closed-shell character of the individual atoms as the elec...

Theoretical studies of actinide compounds have two primary goals. The first is to understand the chemical bonding within these materials and their physical properties. The second goal is to understand the reactivities of actinide compounds. The earliest spectroscopic studies of actinide-containing molecules in the gas phase were carried out using c...

Electronically excited oxygen has an important place in the kinetic schemes of the processes taking place in the atmosphere, in the active medium of an oxygen-iodine laser, and in plasma-assisted combustion ¹ . Over the past decades, a large amount of data on the rate constants of quenching O 2 (b) on a large number of collision partners has been a...

Extremely reactive vibrationally excited ozone O3(υ) molecule is formed in excess of O2 in particular in air-fuel mixture, however there is a lack of kinetic data on O3(υ) reactions with combustion products. The time-resolved absorption spectroscopy method was applied for measurements of the O3 recovery rates after 266 nm photolysis in the presence...

Rate coefficients for the vibrational relaxation of O2(a¹Δ υ) by CO2 have been determined from the decay of fluorescence of the a¹Δg → X³Σg⁻ (υ–υ′) transitions with υ = υ′ = 1, 2 and 3. O2(a¹Δ υ) molecules were produced by pulsed laser photolysis of ozone at a wavelength of 266 nm. The rate coefficients were measured to be (1.9 ± 0.2) × 10⁻¹⁴ cm³/s...

Optically pumped all-rare-gas lasers use metastable rare gas atoms as the lasing species in mixtures with He or Ar buffer gas. The metastables are generated in a glow discharge, and we report model calculations for the optimal production of Ne∗, Ar∗, Kr∗ and Xe∗. Discharge efficiency was estimated by solving the Boltzmann equation. Laser efficiency...

Optically pumped rare gas lasers are being investigated as potential high-energy, high beam quality systems. The lasing medium consists of rare gas atoms (Rg Ne, Ar, Kr, or Xe) that have been electric discharge excited to the metastable np⁵n 1s ³P2 state. Following optical excitation, helium (He) at pressures of 200–1000 Torr is used as the energy...

Optically pumped all-rare-gas lasers (OPRGL) utilize metastable atoms of the heavier rare gases as lasing species. The required number density of metastables for efficient laser operation is 10¹²–10¹³ cm⁻³ in He buffer gas at pressures in the 400–1000 Torr range. Such metastable densities are easily produced in a nanosecond pulsed discharge, even a...

Low energy states of CaO⁺ have been examined by means of two-color threshold ionization spectroscopy. It is established that the ground state is X²Πi and the first excited state, just 685[U+202F]cm⁻¹ higher in energy, is A²Σ⁺. Due to the close proximity of the X²Π1/2 and A²Σ⁺ vibronic levels, they are mutually perturbing via the spin-orbit operator...

Rate constants for the removal of O2 b1Σg+ by collisions with O2, N2, CO2 and H2O have been determined over the temperature range from 297 to 800 K. O2(b1Σg+) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed by observing the temporal behavior of the b1Σg+ - X3Σg- fluorescence. The removal rate constants fo...

Slow electron velocity map imaging (SEVI) spectroscopy was used to examine the BeS⁻ anion to neutral ground state transition, X ²Σ⁺ → X ¹Σ⁺. 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...

The X2Σ+→X1Σ+ 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 oxi...

The electronic structures of ThCl and ThCl⁺ have been examined using laser induced fluorescence and two-photon ionization techniques. Rotationally resolved spectra, combined with the predictions from relativistic electronic structure calculations, show that the ground state of the neutral molecule is Th⁺(7s²6d)Cl⁻, X2Δ3/2. Dispersed fluorescence sp...

Tunable diode laser absorption spectroscopy measurements of the metastable xenon population densities and spectral line broadening of the 904.545 nm transition in three high pressure plasma discharges are presented.

The potential energy curves and spectroscopic constants of ground and many excited states of the RbXe and CsXe van der Waals systems have been determined using a one-electron pseudopotential approach. This has reduced the number of active electrons of the RbXe and CsXe van der Waals systems to only one electron, the valence electron; and has led to...

Optically pumped all-rare-gas laser (OPRGL) with unique properties was recently proposed. To study this promising laser system it is necessary to have reliable diagnostics for the active medium. A set of pressure broadening coefficients, for self- and foreign- gas collision partners, is needed for measurements of the number density of metastable at...

The production of relatively high densities of Ar* metastables (>10¹² cm⁻³) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel...