Adrian M. Gardner

Theoretical study of the bonding in Mn+-RG complexes and the transport of Mn+ through rare gas (M=Ca, Sr, and Ra; n=1 and 2; and RG=He–Rn)

We present high level ab initio potential energy curves for the M(n+)-RG complexes, where n=1 and 2; RG=He-Rn; and M=Ca, Sr, and Ra. Spectroscopic constants have been derived from these potentials and are compared with a wide range of experimental and previous theoretical data, and good agreement is generally seen. Large changes in binding energy, D(e), and bond length, R(e), between M(+)-He, M(+)-Ne, and M(+)-Ar, also found previously in the analogous Ba(+)-RG complexes [M. F. McGuirk et al., J. Chem. Phys. 130, 194305 (2009)], are identified and the cause investigated; the results shed light on the previous Ba(+)-RG results. These unusual trends are not observed for the dicationic complexes, which behave in a fashion similar to the isoelectronic alkali metal ion complexes. The potentials have also been employed to calculate transport coefficients for M(n+) moving through a bath of rare gas (RG) atoms.

Theoretical study of Ban+–RG (RG=rare gas) complexes and transport of Ban+ through RG (n=1,2; RG=He–Rn)

We present high-level ab initio potential energy curves for barium cations and dications interacting with RG atoms (RG = rare gas). These potentials are employed to derive spectroscopic parameters for the Ba(+)-RG and Ba(2+)-RG complexes, and also to derive the transport coefficients for Ba(+) and Ba(2+) moving through a bath of the rare gas. The results are compared to the limited experimental data, which generally show reasonable agreement. We identify a large change in binding energy going from Ba(+)-He and Ba(+)-Ne to Ba(+)-Ar, which is not present in Ba(2+)-RG, and show that this is due to significant dispersion interactions in Ba(+)-RG.

Theoretical Study of M+−RG and M2+−RG Complexes and Transport of M+through RG (M = Be and Mg, RG = He−Rn)

We present high level ab initio potential energy curves for the M(n+)-RG complexes, where n = 1, 2, RG = rare gas, and M = Be and Mg. Spectroscopic constants have been derived from these potentials, and they generally show very good agreement with the available experimental data. The potentials have also been employed in calculating transport coefficients for M(+) moving through a bath of RG atoms, and the isotopic scaling relationship is examined for Mg(+) in Ne. Trends in binding energies, D(e), and bond lengths, R(e), are discussed and compared to similar ab initio results involving the corresponding complexes of the heavier alkaline earth metal ions. We identify some very unusual behavior, particularly for Be(+)-Ne, and offer possible explanations.

Geometries and Bond Energies of the He−MX, Ne−MX, and Ar−MX (M = Cu, Ag, Au; X = F, Cl) Complexes

Calculations on the He...MX, Ne...MX, and Ar...MX (M = Cu, Ag, Au; X = F, Cl) complexes at the CCSD and CCSD(T) levels of theory have been carried out. The geometries of the Ar-MF complexes are in good agreement to those determined via microwave spectroscopy. The RG...MX (RG = He, Ne, and Ar) dissociation energies for these complexes have been evaluated by extrapolation to the complete basis set limit. The importance of the inclusion of diffuse functions to the determined dissociation energies of these complexes are discussed with comparison to recent work. For the He...CuF and He...AuF complexes, the dissociation energies have been found to be significant, at approximately 26 kJ mol(-1), while the bonding in the chlorine analogues is only approximately 15 kJ mol(-1). The bonding between the helium and the metal atoms in the He...CuF and He...AuF complexes has been investigated by using an atoms-in-molecules (AIM) analysis together with an evaluation of the dipole/induced-dipole and ion/induced-dipole interactions. This analysis has shown that the bonding in these complexes is slightly covalent in nature. For the He...AgF and Ne...MF (M = Cu, Ag, Au) complexes the dissociation energy is much smaller and the AIM analysis shows the bonding is more electrostatic in nature. Calculations have also been carried out on He...AgCl and Ne...MCl (M = Cu, Ag, Au) complexes for the first time in addition to the Ar...MX (M = Cu, Ag, Au; X = F, Cl) complexes. The RG...MCl complexes are found to be more weakly bound than the corresponding RG...MF complexes as a result of the difference in electronegativity of the halogen. For each complex, bond lengths, rotational constants, and harmonic vibrational frequencies have also been evaluated.

The 700-1500 cm−1 region of the S1 (Ã1B2) state of toluene studied with resonance-enhanced multiphoton ionization (REMPI), zero-kinetic-energy (ZEKE) spectroscopy, and time-resolved slow-electron velocity-map imaging (tr-SEVI) spectroscopy

We report (nanosecond) resonance-enhanced multiphoton ionization (REMPI), (nanosecond) zero-kinetic-energy (ZEKE) and (picosecond) time-resolved slow-electron velocity map imaging (tr-SEVI) spectra of fully hydrogenated toluene (Tol-h8) and the deuterated-methyl group isotopologue (α3-Tol-d3). Vibrational assignments are made making use of the activity observed in the ZEKE and tr-SEVI spectra, together with the results from quantum chemical and previous experimental results. Here, we examine the 700-1500 cm(-1) region of the REMPI spectrum, extending our previous work on the region ≤700 cm(-1). We provide assignments for the majority of the S1 and cation bands observed, and in particular we gain insight regarding a number of regions where vibrations are coupled via Fermi resonance. We also gain insight into intramolecular vibrational redistribution in this molecule.

Electronic spectroscopy of the Au(6p)–Kr complex

We report electronic absorption spectra, recorded using one- and two-color resonance-enhanced multiphoton ionization spectroscopy, of the Au-Kr complex. The transition is localized on the gold atom, and corresponds to a 6p<--6s atomic excitation; we observe transitions to the D (2)Pi(1/2) and D (2)Pi(3/2) spin-orbit states. In addition, we report the results of ab initio calculations, which consider electronic states arising from the 6 (2)S, 5 (2)D, and 6 (2)P atomic energy levels of Au. Further, we also report an accurate value for the dissociation energy of the ground state of Au-Kr, based on basis set extrapolated RCCSD(T) calculations. The experimental results are discussed in the light of the theoretical ones.

Theoretical study of Al+-RG (RG=He-Rn)

We present the results of CCSD(T) calculations on the full set of Al(+)-RG complexes (RG = He-Rn). Potential energy curves are calculated pointwise, employing the full counterpoise correction and basis sets of quadruple-ζ and quintuple-ζ quality, and then extrapolated to the complete basis set limit. Each curve has been employed to calculate rovibrational energy levels, from which spectroscopic parameters have been derived. These are compared to the available experimental data, and it is seen that there is excellent agreement with the values obtained from both Rydberg state extrapolations and high-resolution laser-induced fluorescence studies. Finally, we have also used our potentials to calculate transport coefficients for Al(+) moving through a bath of RG.

Theoretical study of M(+)-RG2 (M+ = Li, Na, Be, Mg; RG = He-Rn).

Ab initio calculations were employed to determine the geometry (MP2 level), and dissociation energies [MP2 and RCCSD(T) levels], of the M(IIa)(+)-RG2 species, where M(IIa) is a group 2 metal, Be or Mg, and RG is a rare gas (He-Rn). We compare the results with similar calculations on M(Ia)(+)-RG2, where M(Ia) is a group 1 metal, Li or Na. It is found that the complexes involving the group 1 metals are linear (or quasilinear), whereas those involving the group 2 metals are bent. We discuss these results in terms of hybridization and the various interactions in these species. Trends in binding energies, D(e), bond lengths, and bond angles are discussed. We compare the energy required for the removal of a single RG atom from M(+)-RG2 (D(e2)) with that of the dissociation energy of M(+)-RG (D(e1)); some complexes have D(e2) > D(e1), some have D(e2) < D(e1), and some have values that are about the same. We also present relaxed angular cuts through a selection of potential energy surfaces. The trends observed in the geometries and binding energies of these complexes are discussed. Mulliken, natural population, and atoms-in-molecules (AIM) population analyses are performed, and it is concluded that the AIM method is the most reliable, giving results that are in line with molecular orbital diagrams and contour plots; unphysical amounts of charge transfer are suggested by the Mulliken and natural population approaches.

Electronic spectroscopy of the 6p ← 6s transition in Au-Ne: Trends in the Au-RG series

We report electronic spectra of the Au-Ne complex, obtained in the vicinity of the Au atomic 6p <-- 6s transition. The structured spectrum found near the (2)P(3/2) <-- (2)S(1/2) transition is analyzed. We also explain the nonobservance of a spectrum close to the 6(2)P(1/2) state, using the results of high level ab initio calculations and insight from previous work on other Au-RG complexes (where RG = Ar, Kr, and Xe). Basis set extrapolated RCCSD(T) potential energy curves are also presented for the X(2)Sigma(+) ground state of Au-Ne, and the derived D(e) value is compared to experimental values. We then present an overview of trends through the Au-RG series: included in this are calculations on the X states of Au-He and Au-Rn, as well as for Au(+)-He. We also report further calculations on the states which arise from the interaction of Au(6(2)P(J)) with the rare gas atoms and include a Franck-Condon simulation of the D(2)Pi(3/2) <-- X(2)Sigma(1/2)(+) transition for Au-Ar. Trends in the spectroscopy across this series are summarized, and the Hunds case (a)/(c) character discussed.

Theoretical study of the X Σ2+ states of the neutral CM–RG complexes (CM=coinage metal, Cu, Ag, and Au and RG=rare gas, He–Rn)

We present high level ab initio potential energy curves for the X Σ2+ electronic states of the CM–RG complexes; where CM is a coinage metal, CM=Cu, Ag and Au and RG is a rare gas, RG=He–Rn. These potentials are calculated over a range of internuclear separations, R, and the energy at each point is corrected for basis set superposition error and extrapolated to the basis set limit. Spectroscopic constants are determined from the potentials so obtained and are compared to available experimental data. The impact of core-valence correlation to the overall interactions within the complexes involving the lighter RG atoms is also considered. We find that there is a surprising continuous decrease in Re in these species from CM-He to CM-Rn and show that this is likely due to a combination of sp hybridization and small amounts of charge transfer.