The exothermicity of the chemi-ionization reaction Sm + O → SmO(+) + e(-) has been re-evaluated through the combination of several experimental methods. The thermal reactivity (300-650 K) of Sm(+) and SmO(+) with a range of species measured using a selected ion flow tube-mass spectrometer apparatus is reported and provides limits for the bond strength of SmO(+), 5.661 eV ≤ D0(Sm(+)-O) ≤ 6.500 eV. A more precise value is measured to be 5.725 ± 0.07 eV, bracketed by the observed reactivity of Sm(+) and SmO(+) with several species using a guided ion beam tandem mass spectrometer (GIBMS). Combined with the established Sm ionization energy (IE), this value indicates an exothermicity of the title reaction of 0.08 ± 0.07 eV, ∼0.2 eV smaller than previous determinations. In addition, the ionization energy of SmO has been measured by resonantly enhanced two-photon ionization and pulsed-field ionization zero kinetic energy photoelectron spectroscopy to be 5.7427 ± 0.0006 eV, significantly higher than the literature value. Combined with literature bond energies of SmO, this value indicates an exothermicity of the title reaction of 0.14 ± 0.17 eV, independent from and in agreement with the GIBMS result presented here. The evaluated thermochemistry also suggests that D0(SmO) = 5.83 ± 0.07 eV, consistent with but more precise than the literature values. Implications of these results for interpretation of chemical release experiments in the thermosphere are discussed.

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. Thirty vibronic levels of NdO+ arising from eight electronic states were observed with partial rotational resolution. The energy level pattern and supporting electronic structure calculations indicated that all of the observed states correlated with the Nd3+(4f3, 4I)O2− configuration. The structure was consistent with a ligand field theory model where the electronic states of the Nd3+(4f3, 4I) atomic ion define a repeated motif in the electronic state energy intervals of the molecular ion. Comparisons with UO+ show close similarity in the electronic structures of these isoelectronic species.

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 the electronic angular momentum projection Ω = 4. Ab initio calculations were carried out using the spin–orbit state interacting approach with the complete active space second-order perturbation theory method. A series of correlation consistent basis sets were used in conjunction with small-core relativistic pseudopotentials on U to extrapolate to the complete basis set limits. The results for UN correctly obtained an Ω = 3.5 ground state and demonstrated a high density of configurationally related excited states with closely similar ro-vibrational constants. Similar results were obtained for UN+, with reduced complexity owing to the smaller number of outer-shell electrons. The calculated IE for UN was in excellent agreement with the measured value. Improved values for the dissociation energies of UN and UN+, as well as their heats of formation, were obtained using the Feller–Peterson–Dixon composite thermochemistry method, including corrections up through coupled cluster singles, doubles, triples and quadruples. An analysis of the ab initio results from the perspective of the ligand field theory shows that the patterns of electronic states for both UN and UN+ can be understood in terms of the underlying energy level structure of the atomic metal ion.

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(7s6d)Cl, XΔ. Dispersed fluorescence spectra for ThCl revealed the ground state vibrational levels v = 0-10 and low energy electronic states that also originate from the atomic ion 7s6d configuration. Pulsed field ionization-zero kinetic energy photoelectron spectroscopy established an ionization energy (IE) for ThCl of 51 344(5) cm, and the ThCl vibrational term energies of the v = 1-3 levels. The zero-point level of the first electronically excited state was found at 949(2) cm. Comparisons with high-level theoretical results indicate that the ground and excited states are Th(7s6d)Cl XΔ and Th(7s)Cl Σ+1, respectively. Relativistic coupled cluster composite thermochemistry calculations yielded an IE within 1.2 kcal/mol of experiment and a bond dissociation energy (118.3 kcal/mol) in perfect agreement with previous experiments.

New complexes [ZnL](ClO 4) 2 (1), [CdL(ClO 4)]ClO 4 (2) and [HgL](ClO 4) 2 (3) (L = 2,6bis([(2-pyridinylmethyl)thio]methyl)pyridine) were prepared and characterized by X-ray crystallography and variable temperature 1 H NMR. The ligand had an extended planar conformation when crystallized in pure form and a pentadentate corkscrew conformation with the terminal pyridyl nitrogen on either side of the plane formed by the other three donor atoms in the complexes. Nearly symmetric 1 and symmetric 3 had well separated perchlorates. In contrast, 2 had one bidentate perchlorate leading to a N 3 O 2 S 2 metal coordination sphere. Although rapid intermolecular exchange is common for Group 12 metal ion complexes of simple ligands, in dilute CD 3 CN solution slow intermolecular exchange conditions on the δ HH , J CdH and J HgH time scales were found for 1, 2 and 3, respectively, at 20 °C and intramolecular reorganization of bound L approached the slow exchange limit under cryogenic conditions.