Due to the difficultly of working with actinides (radioactive, short lifetimes) and the number of electrons in these systems our chemical understanding either experimentally or theoretically on these systems is very limited. The electronic spectrum of thorium dimer, Th₂, is expected to be heavily congested due to the predicted twelve electronic states within an energy less then 1 eV of the calculated ³∆_g ground state. The chemical bond is predicted to be a quadruple bond in both the ground state and low lying ¹Σ⁺_g state (T_e=400 cm⁻¹)B.J. Roos, P.-Å. Malmqvist and L. Gagliardi, J. Am. Chem. Soc. 128, 17000-17006, 2006 Experimentally Th₂ was been detected in the gas phase by mass spectrometryM.C. Heaven, B.J. Barker and I.O. Antonov, J. Phys. Chem A. 118, 10867-10881, 2014 Here we report on the detection of the gas fluorescence spectrum of Th₂ in the 495-560 nm range via application of 2D LIF spectroscopy and attempts to record high resolution field free and Zeeman spectra. B.J. Roos, P.-Å . Malmqvist and L. Gagliardi, J. Am. Chem. Soc. 128, 17000-17006, 2006. M.C. Heaven, B.J. Barker and I.O. Antonov, J. Phys. Chem A. 118, 10867-10881, 2014.

The gold sulfur bond is becoming ever more important to a vast range of scientific endeavors. We have recorded the electronic spectrum of gas-phase AuS, at vibrational resolution, over the 440-740 nm wavelength range. By application of a synergy of production techniques, hot hollow-cathode sputtering source and cold laser ablation molecular beam source, excitation from both spin components of the inverted ²Π ground state is possible. Excitation into four different excited electronic states involving approximately 100 red-degraded bands has been observed. The four excited states have been characterized as a⁴Σ_1/2, A²Σ⁺_1/2, B²Σ⁻_1/2 and C²∆_i. The observed red-degraded vibronic bands where then globally analyzed to determine an accurate set of term energies and vibrational constants for the excited and ground electronic states. The electronic configurations from which these states arise will be discussed.

In the last few years, the Cheung group in Hong Kong and the Steimle group in Arizona have successfully studied several ruthenium containing diatomic molecules, RuX (X =CF. Wang et al., Journal of Chemical Physics 139, 174318 (2013). ON. Wang et al., Journal of Physical Chemistry A 117, 13279 (2013). NT. Steimle et al., Journal of Chemical Physics 119, 12965 (2003). BN. Wang et al., Chemical Physics Letters 547, 21 (2012)., using the laser-ablation molecular jet technique. Based on this success, the UNB spectroscopy group decided to try and find the optical signatures of other RuX molecules. Using CH₃OH and PH₃ as reactant gases, the RuH and RuP diatomic molecules have been detected in surveys of the 420 - 675 nm spectral region. RuD has also been made using fully deuterated methanol as a reactant. Dispersed fluorescence experiments have been performed to determine ground state vibrational frequencies and the presence of any low-lying electronic states. Rotationally resolved spectra for these molecules have also been taken and the analysis is proceeding. The most recent results will be presented.

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Footnotes:

F. Wang et al., Journal of Chemical Physics 139, 174318 (2013)., N. Wang et al., Journal of Physical Chemistry A 117, 13279 (2013)., T. Steimle et al., Journal of Chemical Physics 119, 12965 (2003)., N. Wang et al., Chemical Physics Letters 547, 21 (2012).)

Recently laser cooling has been demonstrated for the diatomic radical calcium fluoride, CaFV. Zhelyazkova, A. Cournol, T.E. Wall, A. Matsushima, J.J. Hudson, E.A. Hinds, M.R. Tarbutt and B.E. Sauer, Phys. Rev. A 89, 053416 (2014) The mechanism of magneto-optical trapping for diatomic molecules has been elucidated recently by TarbuttM. R. Tarbutt, New J. Phys 17, 015007 (2015)here a rate model was used to model the interaction of molecules with multiple frequencies of laser light. It was shown that the correct choice of laser polarization depends on the sign of the upper state magnetic g-factor. The magnetic tuning of the low rotational levels in the X²Σ⁺, A²Π and B²Σ⁺ electronic states of CaF, have been experimentally investigated using high resolution optical Zeeman spectroscopy of a cold molecular beam sample. The observed Zeeman-induced shifts and splittings were successfully modeled using a traditional effective Hamiltonian approach to account for the interaction between the (ν=0) A²Π and (ν=0) B²Σ⁺ states. The determined magnetic g-factors for the X²Σ⁺, A²Π and B²Σ⁺ states are compared to those predicted by perturbation theory. V. Zhelyazkova, A. Cournol, T.E. Wall, A. Matsushima, J.J. Hudson, E.A. Hinds, M.R. Tarbutt and B.E. Sauer, Phys. Rev. A 89, 053416 (2014). M. R. Tarbutt, New J. Phys 17, 015007 (2015)w

Electronic transition spectrum of the yttrium monophosphide (YP) molecule in the visible region between 715 nm and 880 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The YP molecule was produced by reacting laser - ablated yttrium atoms with PH₃ seeded in argon. Thirteen vibrational bands were analyzed and five electronic transition systems have identified, namely the [12.2] Ω = 3 - X³ Π₂ transition, [13.3] Ω = 3 - X³ Π₂ transition, [13.4] Ω = 3 - X³ Π₂ transition, [13.5] Ω = 3 - X³ Π₂ transition, and [13.4] Ω = 2 - X³ Π₂ transition. Least squares fits of the measured rotational lines yielded molecular constants for the ground and excited states. The ground state symmetry and the bond length r₀ of the YP molecule have been determined to be a X³ Π₂ state and 2.4413 Å respectively in this work. A molecular orbital energy level diagram has been used to help the assignment of the observed electronic states. This work represents the first experimental investigation of the spectrum of the YP molecule.

The B¹Π← X¹Σ⁺ and C¹Σ⁺← X¹Σ⁺ transitions of CaO, at energies below 30,000 cm⁻¹, were previously investigated by LagerqvistA. Lagerqvist, Arkiv För Fysik 8, 83, 1954 The arc source used in that work yielded spectra at energies above 30,000 cm⁻¹ that were too congested for analysis. In the present study we have used jet-cooling of CaO to extend the characterization of the B← X and C← X band systems up to 35,000 cm⁻¹. Analyses of these data and spectroscopic constants will be reported. This work is being carried out in support of two-color photoionization studies of the cation, where the higher energy vibronic levels of the B and C states are used as the first excitation step. A. Lagerqvist, Arkiv För Fysik 8, 83, 1954.

Diatomic nickel boride, NiB, has been produced in the UNB laser ablation molecular jet source. Survey spectra, taken at medium resolution with a pulsed dye laser in the 415 – 510 nm region, showed an intense band system which had previously been observed and assigned as a ²Π_3/2 - ²Σ⁺ transition by Zhen et al.J-f. Zhen, L. Wang, C-b. Qin, Q. Zhang, Y. Chen, Chinese J. Chem. Phys. 23, 626 (2010).sing a single frequency ring dye laser, we have obtained high resolution spectra of the 0-0, 2-0 and 3-0 bands of the most abundant isotopologue, ⁵⁸Ni¹¹B, and the 2-0 band of ⁶⁰Ni¹¹B. The rotational analysis showed that the transition was from an Ω = 0.5 upper state to the ground X²Σ⁺ state. The data were found to fit equally well as ²Σ⁺ - ²Σ⁺ or ²Π_1/2 - ²Σ⁺. The fine structure e/f parity splitting was examined for each of the two options in an attempt to determine the identity of the upper state. Partially resolved hyperfine structure due to the ¹¹B nuclear spin, I = 3/2, was observed and analyzed to try and determine the nature of the boron atom contribution to the ground ²Σ⁺ state configuration. The results of the rotational and hyperfine structure analysis will be discussed. J-f. Zhen, L. Wang, C-b. Qin, Q. Zhang, Y. Chen, Chinese J. Chem. Phys. 23, 626 (2010).U

Transition-metal-containing (TMC) molecules often have very complex electronic spectra because of their large number of low-lying, interacting electronic states, of the large multi-reference character of the electronic states and of the large magnitude of spin-orbit and relativistic effects. As a result, fully ab initio calculations of line positions and intensities of TMC molecules have an accuracy which is considerably worse than the one usually achievable for molecules made up by main-group atoms only. In this presentation we report on new theoretical line lists for scandium hydride ScH and titanium hydride TiHL. Lodi, S. N. Yurchenko and J. Tennyson, Mol. Phys. (Handy special issue) in press. Scandium and titanium are the lightest transition metal atoms and by virtue of their small number of valence electrons are amenable to high-level electronic-structure treatments and serve as ideal benchmark systems. We report for both systems energy curves, dipole curves and various coupling curves (including spin-orbit) characterising their electronic spectra up to about 20 000 cm-1. Curves were obtained using Internally-Contracted Multi Reference Configuration Interaction (IC-MRCI) as implemented in the quantum chemistry package MOLPRO. The curves where used for the solution of the coupled-surface ro-vibronic problem using the in-house program DUO S. N. Yurchenko, L. Lodi, J. Tennyson and A. V. Stolyarov, Computer Phys. Comms., to be submitted. DUO is a newly-developed, general program for the spectroscopy of diatomic molecules and its main functionality will be described. The resulting line lists for ScH and TiH are made available as part of the Exomol project J. Tennyson and S. N. Yurchenko, Mon. Not. R. Astr. Soc. 2012, 425, 21. See also www.exomol.com.

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Footnotes:

L. Lodi, S. N. Yurchenko and J. Tennyson, Mol. Phys. (Handy special issue) in press.. S. N. Yurchenko, L. Lodi, J. Tennyson and A. V. Stolyarov, Computer Phys. Comms., to be submitted.. J. Tennyson and S. N. Yurchenko, Mon. Not. R. Astr. Soc. 2012, 425, 21. See also www.exomol.com..

Transition metal complexes with bipyridine ligands are of great interest in metal-organic chemistry, since they are prototypes for many applications in photochemistry and homogeneous catalysis. Under-coordinated bipyridyl complexes are elusive species in the condensed phase, and the ligand-induced changes in electronic structure are of fundamental interest. We present UV photodissociation spectra of mass-selected monocationic copper(I)-bipyridyl complexes [bpy-Cu-L]⁺ with different ligands (L = H₂O, D₂, N₂, MeOH, Cl). Complexes were prepared via electrospray ionization of copper/bipyridine solutions followed by accumulation and buffer gas cooling in a cryogenic Paul trap. In addition, we show spectra of similar species based on copper oxide, [bpy-CuO-L]⁺.

The 488 nm vibrationally-resolved photoelectron spectra of NbW⁻ and W₂⁻ are reported. The electron affinity of W₂ ( ¹Σ_g⁺ ← ²Σ_u⁺ ) is found to be 1.118 ± 0.007 eV, which differs from the value reported in a previous anion photoelectron spectroscopic study of W₂⁻ (1.46 eV)H. Weidele et al., Chem. Phys. Lett. 237 (1995) 425-431 but was accurately predicted by density functional calculations (1.12 eV)Z. J. Wu, X. F. Ma, Chem. Phys. Lett. 371 (2003) 35-39 The fundamental vibrational frequency of W₂ is measured to be 345 ± 15 cm⁻¹, in agreement with the value previously reported in matrix resonance Raman studies (337 cm⁻¹)Z. Hu, J.-G. Dong, J. R. Lombardi, D. M. Lindsay, J. Chem. Phys. 97 (1992) 8811-8812 The W₂⁻ anion is measured to have a fundamental frequency of 320 ± 15 cm⁻¹. Several weak transitions to excited electronic states are seen and tentatively assigned based on calculated energies. NbW has an electron affinity of 0.856 ± 0.007 eV. Vibrational frequencies are found, by Franck-Condon fitting of overlapping transitions, to be 365 ± 20 cm⁻¹ for NbW⁻ and 410 ± 20 cm⁻¹ for NbW. This increase in vibrational frequency upon photodetachment suggests that the extra electron is in an antibonding orbital, leading to ground state assignments of ³∆ and ²∆ for the anion and neutral, respectively. These results are compared to those obtained for other Group V and Group VI transition metal dimers and trends are discussed.

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Footnotes:

H. Weidele et al., Chem. Phys. Lett. 237 (1995) 425-431, Z. J. Wu, X. F. Ma, Chem. Phys. Lett. 371 (2003) 35-39. Z. Hu, J.-G. Dong, J. R. Lombardi, D. M. Lindsay, J. Chem. Phys. 97 (1992) 8811-8812.

Pure rotational spectra of the rare isotopologues of the TiO radical (X³∆_r) in their natural abundance have been measured using millimeter/submillimeter-wave direct absorption and Fourier transform millimeter-wave (FTmmW) techniques. Between five and seven rotational transitions each of ⁴⁶TiO (8.2 %), ⁴⁷TiO (7.4 %), ⁴⁹TiO (5.4 %), and ⁵⁰TiO (5.2 %) have been recorded for all three spin components in the frequency ranges 62-64 GHz and 255-522 GHz. In the millimeter-wave data, the TiO isotopologues were created in the gas phase from titanium vapor, produced with a specialized Broida-type oven, and N₂O. In the FTmmW spectrometer, laser ablation was used as a titanium source. Titanium hyperfine structure has been fully resolved for both ⁴⁷TiO and ⁴⁹TiO, resulting in distinctive sextets (⁴⁷Ti: I = 5/2) and octets (⁴⁹Ti: I = 7/2) in the millimeter data. The data has been analyzed, and rotation, fine structure, and hyperfine parameters have been determined. These spectroscopic constants are consistent with the past optical data, but have higher precision. TiO has recently been observed in the circumstellar envelope of VY CMa.