Although a wide range of compounds of the heavy rare-gas elements are experimentally known, very few chemically bound molecules have been experimentally observed for the lighter noble gases. Here we report a combined infrared photodissociation spectroscopic and theoretical study on a series of argon-boron oxide cation complexes prepared via a laser vaporization supersonic ion source in the gas phase. Infrared spectroscopic combined with state-of-the-art quantum chemical calculations indicate that the [ArB₃O_4,5]⁺, [ArB₄O₅₋₇]⁺ and [ArB₅O₇]⁺ cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond formed between the in-plane 2p atomic orbitals of Ar and boron. In contrast, the [ArB₃O₄]⁺ cation complex is characterized to be a weakly bound complex with a BO chain structure.

The interaction of Rb 7s ²S_1/2, 5d ²D_3/2,5/2 and 5p ²P_3/2 atoms with the background species at long range (100-1000Å) has been observed by pump-probe ultrafast laser spectroscopy. Parametric four-wave mixing in Rb vapor with pairs of 50-70 fs pulses produces coherent Rb 6P-5S emission at 420 nm that is modulated by Rb quantum beating. The two dominant beating frequencies are 18.2 THz and 2.07 THz, corresponding to quantum beating between 7S and 5D states and to the (5D-5P_3/2)-(5P_3/2-5S) defect, respectively. Analysis of Rabi oscillations in these pump-probe experiments allows for the mean interaction energy at long range to be determined. r0pt Figure

A significant step forward in the structure-activity relationships of sweeteners was the assignment of the AH-B moiety in sweeteners by Shallenberger and Acree R. S. Shallenberger, T. E. Acree. Nature 216, 480-482 Nov 1967.^,R. S. Shallenberger. Taste Chemistry; Blackie Academic & Professional, London, (1993). They proposed that all sweeteners contain an AH−B moiety, known as glucophore, in which A and B are electronegative atoms separated by a distance between 2.5 to 4 Å. H is a hydrogen atom attached to one of the electronegative atom by a covalent bond. For saccharine, one of the oldest artificial sweeteners widely used in food and drinks, two possible B moieties exist ,the carbonyl oxygen atom and the sulfoxide oxygen atom although there is a consensus of opinion among scientists over the assignment of AH−B moieties to HN−SO. In the present work, the solid of saccharine (m.p. 220ºC) has been vaporized by laser ablation (LA) and its rotational spectrum has been analyzed by broadband CP−FTMW and narrowband MB−FTMW Fourier transform microwave techniques. The detailed structural information extracted from the rotational constants and ^14 R. S. Shallenberger. Taste Chemistry; Blackie Academic Professional, London, (1993)..

r0pt Figure In the realm of small-molecule van der Waals interactions, there exists much experimental and theoretical data for most fundamental atmospheric components. For complexes containing O₂, however, there is actually very little experimental data. This is most likely due to the spin complications brought about by the ³Σ state of the molecule. In this talk, the authors will detail the first known measurement of the complex O₂-HCl along with experimental and theoretical analyses of the complex. Previously measured O₂-HFS. Wu, G. Sedo, E. M. Grumstrup, and K. R. Leopold, J. Chem. Phys., 127 (2007) 204315.nalysis have been used as a guide and this talk will outline similarities and differences in the two species.

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S. Wu, G. Sedo, E. M. Grumstrup, and K. R. Leopold, J. Chem. Phys., 127 (2007) 204315.a

Thorough the detailed analysis of the hyperfine resolved rotational transitionsA. Mizoguchi, S. Ota, H. Kanamori, Y. Sumiyoshi, and Y. Endo, J. Mol. Spectrosc, 250, 86 (2008)Z. T. Dehghani, S. Ota, A. Mizoguchi and H. Kanamori, J. Phys. Chem. A, 117(39), 10041, (2013), we have been pointed out that there exists not a little interaction between ortho and para states in the molecular Hamiltonian of S₂Cl₂. Using the ortho-para mixed molecular wavefunctions derived from the Hamiltonian, we calculated the transition moment and frequency of the ortho-para forbidden transitions in the cm- and mm-wave region, and picked up some promising candidate transitions for the spectroscopic detection. In the experiment, the S₂Cl₂ vapor with Ar buffer gas in a supersonic jet condition was used with FTMW spectrometer at National Chiao Tung University. As a result, seven hyperfine resolved rotational transitions in the cm-wave region were detected as the ortho-para transition at the predicted frequency within the experimental error range. The observed intensity was 10⁻³ smaller than that of an allowed transition, which is also consistent with the prediction. This is the first time the electric dipole transition between ortho and para states has been detected in a free isolated molecule.

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A. Mizoguchi, S. Ota, H. Kanamori, Y. Sumiyoshi, and Y. Endo, J. Mol. Spectrosc, 250, 86 (2008)

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Small protonated water clusters and their argon tagged analogues of the general formula H⁺(H₂O)_nAr_m have been generated in a pulsed electric discharge source. Clusters containing n=1−8 water molecules were mass-selected and their absorptions in the near-infrared were probed with a tunable Nd\colonYAG pumped OPA/OPA laser system in the region from 4850−7350 cm⁻¹. A doublet corresponding to overtones of the free O−H stretches of the external waters was observed around 7200 cm⁻¹ that was continuously decreasing in intensity with increasing cluster size. Broad, mostly featureless absorptions were found around 5300 cm⁻¹ associated with stretch/bend combinations and with the hydrogen bonded waters in the core of the clusters. Vibrational assignments were substantiated by comparison to anharmonic frequency computations via second-order vibrational perturbation theory (VPT2) at the MP2/aug-cc-pVTZ level of theory.

Accurate structure determination of large molecules still represents an ambitious challenge. Interesting benchmark systems for structure determination are large diamondoid dimers, whose structures are governed by strong intramolecular interactions. Recently, diamondoid dimers with unusually long central C–C bonds (up to 1.71 Å) were synthesized. This long central C-C bond was rationalized by numerous CH···HC-type dispersion attractions between the two halves of the molecule. The thermodynamic stabilization of molecules equipped with bulky groups has provided a conceptually new rationale, since until then it had been assumed that such molecules are highly unstable. We performed a broadband CP-FTMW spectroscopy study in the 2-8 GHz frequency range on oxygen-substituted diamondoid dimers (C₂₆H₃₄O₂, 28 heavy atoms) as well as diadamantyl ether to provide further insight into their structures. The experimental data are compared with results from quantum-chemical calculations and gas-phase electron diffraction. For the ether, we even obtained ¹³C and ¹⁸O isotopologues to generate the full heavy-atom substitution structure.

Vibrational sum frequency generation (VSFG) spectroscopy is used to study the effect of room temperature ionic liquids (RTILs) in situ at the electrical double layer (EDL). RTILs have been recognized as electrolytes without solvent for applications in batteries, supercapacitors and electrodeposition¹. The molecular response of the RTIL in the EDL affects the performance of these devices. We use the vibrational Stark effect on CO as a probe to detect the changes in the electric field affected by the RTIL across the EDL on metal electrodes. The Stark effect is a shift in the frequency in response to an externally applied electric field and also influenced by the surrounding electrolyte and electrode². The CO Stark shift is monitored by the CO-VSFG spectra on Pt or Ag in a range of different imidazolium-based RTILs electrolytes, where their composition is tuned by exchanging the anion, the cation or the imidazolium functional group. We study the free induction decay (FID)³ of the CO to monitor how the RTIL structure and composition affect the vibrational relaxation of the CO. Combining the CO vibrational Stark effect and the FID allow us to understand how the RTIL electrochemical response, molecular orientation response and collective relaxation affect the potential drop of the electric field across the EDL, and, in turn, how determines the electrical capacitance or reactivity of the electrolyte/electrode interface. ¹Fedorov, M. V.; Kornyshev, A. A., Ionic Liquids at Electrified Interfaces. Chem. Rev. 2014, 114, 2978-3036. ² (a) Lambert, D. K., Vibrational Stark Effect of Adsorbates at Electrochemical Interfaces. Electrochim. Acta 1996, 41, 623-630. (b) Oklejas, V.; Sjostrom, C.; Harris, J. M., SERS Detection of the Vibrational Stark Effect from Nitrile-Terminated SAMs to Probe Electric Fields in the Diffuse Double-Layer. J. Am. Chem. Soc. 2002, 124, 2408-2409. ³Symonds, J. P. R.; Arnolds, H.; Zhang, V. L.; Fukutani, K.; King, D. A.,Broadband Femtosecond Sum-Frequency Spectroscopy of CO on Ru{1010} in the Frequency and Time Domains. J. Chem. Phys. 2004, 120, 7158-7164.

Despite the harsh conditions for chemical conversion, ethylene oxide produced from ethylene epoxidation on Ag-based heterogeneous catalyst constitutes one of the largest volume chemicals in chemical industry. Recently, photocatalytic epoxidation of ethylene over plasmonic Ag nanoparticles enables the chemical conversion under significantly decreased temperature and ambient pressure conditions. Yet a detailed understanding of the photocatalytic process at the reactant/catalyst interface is under debate. Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that enables the localized detection of rare and/or transient chemical species with high sensitivity under in situ and ambient conditions. Using SERS, we are able to monitor at individual sites of an Ag nanocatalyst the visible-light-mediated adsorption and epoxidation of ethylene. From detected intermediates, we find that the primary step in the photoepoxidation is the transient formation of graphene catalyzed by the Ag surface. Density functional theory (DFT) simulations that model the observed SERS spectra suggest that the defective edge sites of the graphene formed on Ag constitute the active site for C2H4 adsorption and epoxidation. Further studies with pre-formed graphene/Ag catalyst composites confirm the indispensable role of graphene in visible-light-mediated ethylene epoxidation. Carbon is often thought to be either an innocent support or a poison for metallic catalysts; however our studies reveal a surprising role for crystalline carbon layers as potential co-catalysts.