Rivaled, perhaps, only by its neighbor carbon, boron encompasses a unique and diverse swath of chemistry that lends itself to the adoption of extraordinary characteristics when complexed to metals. In recent years, metal-boride clusters have garnered attention for their potential application in a variety of fields including hydrogen storage and high energy density fuels. As inorganic ligands, these boron clusters tend to prefer multiply aromatic (σ- and π-) electronic configurations which may contribute to their unusual stability and unique properties. In the present study, a series of cerium-boride clusters were interrogated using anion photoelectron spectroscopy as a means of reconciling the presence of a series of mass coincident CeB_x⁻ (x = 5-7) and CeO₂B_y⁻ (y = 2-4) clusters as well as elucidating the electronic structure of the anionic and neutral species. Unlike previously studied cerium-oxide clusters, which typically have binding energies around 0.7-1.2 eV, the boride clusters have exhibited greater electron affinities between 1.0-2.0 eV. Moreover, the spectra collected show pronounced vibrational progressions that aid in the analysis of the clusters’ molecular structure.

The pure rotational spectrum of ZnBr (²Σ⁺) has been recorded using millimeter-wave direct absorption spectroscopy. This species was generated in the gas phase via the reaction of zinc vapor with CH₃Br in the presence of a DC discharge. Multiple rotational transitions were measured for 6 isotopologues (⁶⁴Zn⁷⁹Br, ⁶⁴Zn⁸¹Br, ⁶⁶Zn⁷⁹Br, ⁶⁶Zn⁸¹Br, ⁶⁸Zn⁷⁹Br, and ⁶⁸Zn⁸¹Br) in the frequency range of 270-300 GHz, each of which consisted of spin-rotation splittings. Furthermore, transitions originating in the v = 1 through 3 excited vibrational states for certain isotopologues were obtained. The equilibrium rotational constant for ⁶⁴Zn⁷⁹Br (B_e) was calculated to be near 2780 MHz, resulting in an equilibrium bond length (r_e) of 2.25 Å.

The Pd+CO reaction has been reinvestigated using deposition of ground state reagents in solid argon and neon and the formation of Pd_nCO (n=2-5) is evidenced by strong absorption in the range 2015-1650 cm⁻¹. Various isotopic data ( ¹²C/¹³C,¹⁶O /¹⁸O, natural isotopes for the palladium) and number of two quantum transitions have been measured in the near- and far-infrared regions. In argon, selective irradiation in visible leads to conversion between two Pd₂CO isomers distinguished by the stretching frequency of the diatomic CO: bridged T-shaped (ν_CO= 1856 cm⁻¹) and side on (ν_CO= 2015 cm⁻¹). DFT calculations of the geometrical and electronic properties of Pd_nCO complexes are also presented and compared to the experimental values.

Ytterbium monofluoride, YbF, has long been used as a venue in attempts to measure the electron electric dipole moment (eEDM)Hudson, J. J.; Sauer, B. E.; Tarbutt, M. R.; Hinds, E. A., Measurement of the Electron Electric Dipole Moment Using YbF Molecules. Phys. Rev. Lett. 2002, 89 (2), 023003/1-023003/4.Tarbutt, M. R.; Sauer, B. E.; Hudson, J. J.; Hinds, E. A., Design for a fountain of YbF molecules to measure the electron's electric dipole moment. New J. Phys. 2013, 15 (May), 053034/1-053034/17. . In addition to the molecular EDM resulting from the eEDM contribution, the ¹⁷³Yb(16.1%, I=5/2) isotopic form of Yb-containing molecules are also expected to have an EDM caused by an interaction of a nuclear magnetic quadrupole moment (NMQM)Lackenby, B. G. C.; Flambaum, V. V., Weak quadrupole moment, quadrupole distribution of neutrons and Lorentz invariance violation in deformed nuclei. arXiv.org, e-Print Arch., Nucl. Theory 2017, 1-7.ith the electrons. As pointed out by Kozyryev and HutzlerKozyryev, I.; Hutzler, N. R., Precision measurement of time-reversal symmetry violation with laser-cooled polyatomic molecules. arXiv.org, e-Print Arch., Phys. 2017, 1-11. certain energy levels of Yb-polyatomic molecules (e.g. YbOH, YbCCH, YbCH₃, and YbOCH₃) are expected to exhibit enhanced sensitivity for EDM measurements, relative to YbF, largely due to their ease of polarization. The properties of such molecules are poorly characterized. Here we report on our initial molecular beam studies of the knownMelville, T. C.; Coxon, J. A., The visible laser excitation spectrum of YbOH: The A²Π_1/2(000) - X²Σ⁺(000) transition. J. Chem. Phys. 2001, 115 (15), 6974-6978.²Π_1/2(000) - X²Σ⁺(000) transition of YbOH. The high-resolution ( 30 MHz) laser induced fluorescence (LIF) spectrum in the 17320 cm⁻¹ to 17326 cm⁻¹ range was recorded both field-free and in the presence of a static electric field. Stark spectra were analyzed to determine the molecular frame permanent electric dipole moments, μ_el, for the A²Π_1/2 and X²Σ⁺ states. The dispersed fluorescence resulting from the excitation of rotationally resolved branch features has been analyzed to produce fluorescence branching ratios. Implications for planned EDM measurements will be presented. Hudson, J. J.; Sauer, B. E.; Tarbutt, M. R.; Hinds, E. A., Measurement of the Electron Electric Dipole Moment Using YbF Molecules. Phys. Rev. Lett. 2002, 89 (2), 023003/1-023003/4.

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Lackenby, B. G. C.; Flambaum, V. V., Weak quadrupole moment, quadrupole distribution of neutrons and Lorentz invariance violation in deformed nuclei. arXiv.org, e-Print Arch., Nucl. Theory 2017, 1-7.w Kozyryev, I.; Hutzler, N. R., Precision measurement of time-reversal symmetry violation with laser-cooled polyatomic molecules. arXiv.org, e-Print Arch., Phys. 2017, 1-11., Melville, T. C.; Coxon, J. A., The visible laser excitation spectrum of YbOH: The A²Π_1/2(000) - X²Σ⁺(000) transition. J. Chem. Phys. 2001, 115 (15), 6974-6978.A

Alkaline earth monoalkoxide free radicals, e.g., CaOCH₃, CaOCH₂CH₃, and CaOCH(CH₃)₂, have been proposed recently as candidates for future laser cooling of polyatomic molecules.Kozyryev, L. Baum, K. Matsuda and J. M. Doyle, ChemPhysChem 17, 3641 (2016).heir à ← X̃ and B̃ ← X̃ electronic transitions correspond to promotion of the unpaired electron in the 4s orbital of Ca⁺ to each of the three components of its 4p orbital perturbed by the presence of the alkoxy group. These electronic transitions are limited to unbonding orbitals, from which the existence of quasiclosed transition loops for laser cooling has been surmised. Moreover, molecules suitable for Doppler cooling with lasers must feature (quasi-)diagonal Franck-Condon (FC) matrices for transitions between vibronic levels involved in the closed transition cycles, which is expected for alkaline earth monoalkoxides thanks to their bonding scheme. Laser-induced fluorescence (LIF) and dispersed-fluorescence (DF) spectra can provide valuable information to guild future laser cooling experiments. Experimentally obtained vibronic transition frequencies and intensities have been used to benchmark ab initio calculations carried out using both complete active space self-consistent field (CASSCF) and coupled cluster (CC) methods. Although FC factor calculations using the harmonic oscillator approximation reproduce major peaks in the spectra, it has been found that Jahn-Teller (JT) and pseudo-Jahn-Teller (pJT) effects introduce certain new transitions. Furthermore, The à state of alkaline earth monoalkoxides is split by the spin-orbit interaction and, for those free radicals with symmetry lower than C_3v, the difference potential between two nearly degenerate electronic states. The rotational and fine structure of the involved electronic states as well as line intensities for rotational transitions between these states are predicted using a newly proposed spectroscopic model. The implications of the present experimental and computational investigations to future laser cooling experiments will be discussed.

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Kozyryev, L. Baum, K. Matsuda and J. M. Doyle, ChemPhysChem 17, 3641 (2016).T

Laser-induced fluorescence (LIF) and dispersed-fluorescence spectroscopy (DF) spectroscopic investigations of à ← X̃ transitions of a series of calcium monoalkoxides, including CaOCH₃, CaOCH₂CH₃, and CaOCH(CH₃)₂, have been carried out. The free radicals were produced by laser ablation of a calcium rod in the presence of alkohols under jet-cooled conditions. Dominant transitions in the vibrationally resolved LIF and DF spectra obtained by pumping the orgin bands are reproduced using Franck-Condon (FC) factors calculated by complete active space self-consistent field (CASSCF) as well as coupled cluster (CC) methods. DF spectra obtained by pumping other vibronic bands in the LIF spectra provide valuable information about the FC matrices and aid the assignment of vibronic transitions. The (pseudo-)Jahn-Teller effects introduce transitions that are not predicted using the harmonic oscillator approximation.

Coupled-cluster calculations of low-lying electronic states for heavy-metal containing diatomic molecules (e.g., PtH, ThO⁺, ThN, BaO⁺, CsF⁺) are reported. Recently-developed relativistic quantum-chemical techniques have been used, including an atomic mean-field approach for efficent construction of spin-orbit integrals [1], a perturbative approach for treating spin-orbit coupling within exact-two-component equation-of-motion coupled-cluster methods [2], and a new implementation of two-component coupled-cluster methods for non-perturbative treatments of spin-orbit coupling [3]. Bond lengths, vibrational frequencies, and dipole moments of these molecules containing heavy metals are compared with experimental data to assess the accuracy and usefulness of the computational methods.

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J. Liu and L. Cheng, J. Chem. Phys. submitted.

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L. Cheng, F. Wang, J. F. Stanton, and J. Gauss, J. Chem. Phys. 148, 044108 (2018).

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J. Liu, Y. Shen, A. Asthana, and L. Cheng, J. Chem. Phys. 148, 034106 (2018).

Serious draw backs to nuclear power include long-term nuclear waste storage and amelioration of the existing waste. The 4% enriched uranium fuel used in a typical light water reactor is converted to spent nuclear fuel (SNF) made up of 3% fission products, of which  ∼ 30% are lanthanides (Ln), and 1% transuranium actinide (Ac) elements Np, Pu, Am and Cm. Partitioning of the Ln from the Ac present in the SNF by developing element-specific ligands for solvent extraction is a one of the most challenging facet of nuclear waste processing.Leoncini, A.; Huskens, J.; Verboom, W., Ligands for f-element extraction used in the nuclear fuel cycle. Chem. Soc. Rev. 2017, 46 (23), 7229-7273.ystematic experimental and theoretical studies of simple Ac and Ln containing molecules is one avenue for garnering insight into element-specific ligation.Heaven, M. C.; Barker, B. J.; Antonov, I. O., Spectroscopy and Structure of the Simplest Actinide Bonds. J. Phys. Chem. A 2014, 118 (46), 10867-10881.s part of an effort to establish trends in Th-X bonding, a combined experimental and theoretical study of ThN has been undertaken. High-resolution ( ∼ 30MHz) LIF spectroscopy, both field-free and in the presence of static magnetic and electric fields, were recorded. A strong band near 555 nm, which was not previously detected via REMPI spectroscopy ^b has been assigned to a [18.0]²Π_3/2 - ²Σ⁺ transition. The determined fine structure parameters, electric dipole moments, and magnetic g-factors will be discussed in terms of the present, and previous^b, ab initio predictions.

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Leoncini, A.; Huskens, J.; Verboom, W., Ligands for f-element extraction used in the nuclear fuel cycle. Chem. Soc. Rev. 2017, 46 (23), 7229-7273.S Heaven, M. C.; Barker, B. J.; Antonov, I. O., Spectroscopy and Structure of the Simplest Actinide Bonds. J. Phys. Chem. A 2014, 118 (46), 10867-10881.A

A systematic experimental and theoretical studies of simple Ac and Ln containing molecules is one avenue for garnering insight into element-specific ligationHeaven, M. C.; Barker, B. J.; Antonov, I. O., Spectroscopy and Structure of the Simplest Actinide Bonds. J. Phys. Chem. A 2014, 118 (46), 10867-10881. Here we report on the high resolution ( ∼ 30 MHz) laser induced fluorescence (LIF) spectra of supersonic cooled molecular beam of ThCl produces in the reaction of laser ablated Th with an Ar/CCl₄ mixture. The present work builds on the recent LIF, dispersed fluorescence, and REMPI study of the Heaven and Peterson groupsVan Gundy, R. A.; Bartlett, J. H.; Heaven, M. C.; Battey, S. R.; Peterson, K. A., Spectroscopic and theoretical studies of ThCl and ThCl⁺. J. Chem. Phys. 2017, 146 (5), 054307/1-054307/8. Analysis of a band near 550 nm has been assigned as the [18.2]1.5-X²Π_3/2transition. Observed doubling the lines has shown to be caused Ω-doubling in the upper state. No ³⁵Cl(I=3/2) hyperfine splitting was observed. Progress on recording the electric dipole moments and magnetic g-factors will be reported. Interpretation of the spectrum is based, in part, upon previously published electronic structure prediction and a simple molecular orbital correlation diagram.

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Heaven, M. C.; Barker, B. J.; Antonov, I. O., Spectroscopy and Structure of the Simplest Actinide Bonds. J. Phys. Chem. A 2014, 118 (46), 10867-10881.. Van Gundy, R. A.; Bartlett, J. H.; Heaven, M. C.; Battey, S. R.; Peterson, K. A., Spectroscopic and theoretical studies of ThCl and ThCl⁺. J. Chem. Phys. 2017, 146 (5), 054307/1-054307/8..