After the discovery of C₆₀,H. W. Kroto, J. R. Heath, S. C. O'Brian, R. E. Curl & R. E. Smalley, Nature, 318, 162, 1985he question of its relevance to the diffuse interstellar bands was raised. In 1987 H. W. Kroto wrote: "The present observations indicate that C₆₀ might survive in the general interstellar medium (probably as the ion C₆₀ ⁺)".H. W. Kroto in "Polycyclic aromatic hydrocarbons and astrophysics", eds. A. Leger, L. B. d'Hendecourt & N. Boccara, Reidel, Dordrecht, 1987, p.197n 1994 two diffuse interstellar bands (DIBs) at 9632 and 9577 Å were detected and proposed to be the absorption features of C₆₀ ⁺.B. H. Foing & P. Ehrenfreund, Nature, 369, L296, 1994his was based on the proximity of these wavelengths to the two prominent absorption bands of C₆₀ ⁺ measured by us in a neon matrix in 1993.J. Fulara, M. Jakobi & J. P. Maier, Chem. Phys. Lett., 211, 227, 1993onfirmation of the assignment required the gas phase spectrum of C₆₀ ⁺ and has taken 20 years. The approach which succeeded confines C₆₀ ⁺ ions in a radiofrequency trap, cools them by collisions with high density helium allowing formation of the weakly bound C₆₀ ⁺-He complexes below 10 K. The photofragmentation spectrum of this mass-selected complex is then recorded using a cw laser. In order to infer the position of the absorption features of the bare C₆₀ ⁺ ion, measurements on C₆₀ ⁺-He₂ were also made. The spectra show that the presence of a helium atom shifts the absorptions by less than 0.2 Å, much less than the accuracy of the astronomical measurements. The two absorption features in the laboratory have band maxima at 9632.7(1) and 9577.5(1) Å, exactly the DIB wavelengths, and the widths and relative intensities agree. This leads to the first definite identification of now five bands among the five hundred or so DIBs known and proves the presence of gaseous C₆₀ ⁺ in the interstellar medium.E. K. Campbell, M. Holz, D. Gerlich & J. P. Maier, Nature, 523, 323, 2015G. A. H. Walker, D. A. Bohlender, J. P. Maier & E. Campbell, Astrophys. J. Lett., 812, L8, 2015he absorption of cold C₇₀ ⁺ has also been obtained by this approach. In addition the electronic spectra of a number of cations of astrophysical interest ranging from those of carbon chains including oxygen to larger polycyclic aromatic hydrocarbon could be measured in the gas phase at around 10 K in the ion trap but using an excitation-dissociation approach. The implications of these laboratory spectra in relation to the diffuse interstellar band absorptions can be discussed.

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Footnotes:

H. W. Kroto, J. R. Heath, S. C. O'Brian, R. E. Curl & R. E. Smalley, Nature, 318, 162, 1985t H. W. Kroto in "Polycyclic aromatic hydrocarbons and astrophysics", eds. A. Leger, L. B. d'Hendecourt & N. Boccara, Reidel, Dordrecht, 1987, p.197I B. H. Foing & P. Ehrenfreund, Nature, 369, L296, 1994T J. Fulara, M. Jakobi & J. P. Maier, Chem. Phys. Lett., 211, 227, 1993C E. K. Campbell, M. Holz, D. Gerlich & J. P. Maier, Nature, 523, 323, 2015  G. A. H. Walker, D. A. Bohlender, J. P. Maier & E. Campbell, Astrophys. J. Lett., 812, L8, 2015T

I will first recall how [the two Newton's equations, 1rst year of university] one can very easily compute the rotational and translational classical dynamics of an ensemble of linear molecules interacting through an (input) pair-wise intermolecular potential. These Classical Molecular Dynamics Simulations (CMDS), which provide the time dependence of the positions and axis-orientations of gas phase molecules, are then used to calculate a number of pressure effects manifesting in absorption and scattering spectra. The cases of CO2, O2 and N2 will be considered, systems for which fully quantum approaches are intractable, and comparisons with measured data will be made, free of any adjusted parameter. I will show that, with a few input ingredients from literature (molecule geometry, electric multipoles, polarizabilities, ...) an no adjusted parameter, excellent agreements with various measurements are obtained. Examples will be given for: (1) Collision induced absorption (due to the interaction induced dipole) ; (2) The far wings of absorption (due to the dipole) and light scattering (due to polarizability) bands ; (3) The broadening and shapes (with their deviations from the Voigt profile) of individual absorption lines for both "free" and spatially tightly confined gases. If times allows, additional demonstrations of the interest of CMDS will be given by considering line-mixing effects and the relaxation of laser-kicked molecules.

Molecular spectroscopy has been a powerful tool in the study of molecules in gas phase, condensed phase, and at interfaces. The transition from in vitro spectroscopy to spectroscopic imaging of living systems is opening new opportunities to reveal cellular machinery and to enable molecule-based diagnosis (Science 2015, 350: 1054). Such a transition involves more than a simple combination of spectrometry and microscopy. In this presentation, I will discuss the most recent efforts that have pushed the physical limits of spectroscopic imaging in terms of spectral acquisition speed, detection sensitivity, spatial resolution and imaging depth. I will further highlight significant applications in functional analysis of single cells and in label-free detection of diseases.

Small metal containing molecules are ideal venues for testing Fundamental Physics, investigating relativistic effects, and modelling spin-orbit induced unimolecular dynamics. Electronic spectroscopy is an effective method for probing these phenomena because such spectra are readily recorded at the natural linewidth limited resolution and accuracy of 0.0001 cm⁻¹. The information garnered includes fine and hyperfine interactions, magnetic and electric dipoles, and dynamics. With this in mind, three examples from our recent (unpublished) studies will be highlighted. SiHD: Long ago Duxbury et al.G. Duxbury, A. Alijah and R. R. Trieling, J. Chem. Phys. 98, 811 (1993)eveloped a semi-quantitative model invoking Renner-Teller and spin-orbit coupling of the ã³B₁, ~X¹A₁, and ùB₁, states to explain the observed local perturbations and anomalous radiative lifetimes in the visible spectrum. More recently, the ã³B₁ to ùB₁ intersystem crossing has been modeled using both semi-classical transition state theory and quantum trajectory surface hopping dynamics R. R. Zaari and S. A. Varganov, JPCA 119 , 1332 (2015) Here we investigate the effects of the reduced symmetry of SiHD on the spectroscopy and dynamics using 2D spectroscopy N. J. Reilly, T. W. Schmidt and S. H. Kable, JPCA 110, 12355(2006) Rotationally resolved lines in the origin ~X¹A'→ ùA" band are assigned to both c-type transitions and additional axis-switching J. T. Hougen and J. K. G. Watson, Can. J. Phys. 43 , 298 (1965)nduced transitions. AuO and AuS: The observed markedly different bonding of thiols and alcohols to gold clusters should be traceable to the difference in Au-O and Au-S bonding. To investigate this difference we have used optical Stark and Zeeman spectroscopy to determine the permanent electric dipole moments and magnetic g-factors. The results are rationalized using simple m.o. correlation diagrams and compared to ab initio predictions. TaN: TaN is the best candidate to search for a T,P- violating nuclear magnetic quadrupole momentL. V. Skripnikov, et.al. Phys. Rev. A: 92, 1 (2015) Here we report on the optical 2D, Stark, and Zeeman spectra, and our efforts to record the pure rotational spectrum using the separated field pump/probe microwave-optical double resonance.Implications for T,P- violating experiments will be presented.

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Footnotes:

G. Duxbury, A. Alijah and R. R. Trieling, J. Chem. Phys. 98, 811 (1993)d R. R. Zaari and S. A. Varganov, JPCA 119 , 1332 (2015). N. J. Reilly, T. W. Schmidt and S. H. Kable, JPCA 110, 12355(2006). J. T. Hougen and J. K. G. Watson, Can. J. Phys. 43 , 298 (1965)i L. V. Skripnikov, et.al. Phys. Rev. A: 92, 1 (2015).