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The 70th International Symposium on Molecular Spectroscopy
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has facilitated investigation of the well-known HOCO intermediate. Okumura and co-workers have also studied the conversion of acrylic acid to vinyl radical and DOCO, revealing HOD and HCCD as important intermediates at the beginning of the reaction. It will be interesting to follow the future of these state-of-the art measurements, which are quickly approaching the sensitivities of CW cavity ring down experiments. Jens-Uwe Grabow (Institut für Physikalische Chemie and Elektrochemie) presented details on recent advancements in high-sensitivity microwave spectroscopy. His group utilizes high-resolution microwave spectroscopy to identify interstellar molecules, assign molecular conformations, investigate the motions and binding of biomolecules, and distinguish chiral species [Grabow, J.-U. Angew. Chem., Int. Ed. 2013, 52, 11698]. A cold molecular beam of the target species is generated via supersonic jet expansion and interrogated with microwave radiation in a reflective cavity. To increase the sensitivity of their broadband microwave source, the radiation is reflected several times across the expansion in a method called I/Q modulated passage acquired coherence technique (IMPACT) FT-MW. As is the case in NMR spectroscopy, the Grabow group is able to manipulate the density matrix of a molecule by applying (π/2) and π pulses, which tip the net dipole vector according to the Bloch equations. Using the three-wave-mixing scheme developed in Melanie Schnell’s group at the MaxPlanck Institute, different enantiomers can be distinguished by the π radian phase difference between their “listen” signals [Shubert, V. A.; et al. Angew. Chem., Int. Ed. 2014, 53, 1152]. Martina Havenith (Ruhr University Bochum) outlined a novel application of terahertz (THz) spectroscopy. Her group works closely with theoreticians such as Dominik Marx (Ruhr University Bochum) to capture the broad absorption profiles of bulk water and solutions in the THz region [Sun, J.; et al. J. Am. Chem. Soc. 2014, 136, 5031]. By Fourier transform of the autocorrelation function of the dipole moment, they have shed light on the picosecond time scale motions that are responsible for these bands. For example, she described how the THz electric field can modulate the position of cation or anion solutes within their first solvation shell, leading to strong THz absorptions that evolve as a function of solute concentration. She also described how the spectroscopic response to isotopic substitution (H/D exchange) can be used to identify rocking vibrations of amino acids, such as glycine, against surrounding water molecules. A broader goal of this research is to use THz spectroscopy to follow the reorganization of solvent molecules to maximize the enthalpy and minimize the entropy in the formation of protein complexes. Arthur G. Suits (Wayne State University) delivered an insightful overview of his group’s advancements in performing chirped-pulse microwave spectroscopy on pulsed uniform flows (CPUF) [Oldham, J. M.; et al. J. Chem. Phys. 2014, 141, 154202; Abeysekera, C.; et al. J. Chem. Phys. 2014, 141,
rom June 22 to 26, 2015, spectroscopists from over 25 countries were warmly welcomed to the University of Illinois at Urbana−Champaign (UIUC) by Provost Ilesanmi Adesida, for the 70th International Symposium on Molecular Spectroscopy (ISMS). Prof. Benjamin J. McCall, Birgit McCall, and the UIUC team are commended for their outstanding organization and implementation of the meeting program. Also, the Coblenz Society and The Journal of Physical Chemistry A are acknowledged for their support of the barbeque. This report summarizes the presentations of the plenary speakers and award recipients mentioned in Table 1, as well as a few memorable talks from the mini-symposia. An exhaustive list of presenters and abstracts can be found on the conference Web site: isms.illinois.edu. Table 1. ISMS 2015 Plenary Speakers and Award Recipients Plenary Speakers Mitchio Okumura
California Institute of Technology Jens-Uwe Grabow Institut für Physikalische Chemie and Elektrochemie Martina Havenith Ruhr University, Bochum Arthur G. Suits Wayne State University Award Recipients Grant T. Buckingham (University of Rao Prize Colorado) Kathryn Chew (Yale University) Rao Prize Yu-Hsuan Huang (National Chiao Tung Rao Prize University) Christopher M. Levitt (University of Miller Prize Georgia) Emilio J. Cocinero (Universidad del Paiś Flygare Award Vasco) Richard Dowes (Missouri University of Flygare Award Science and Technology) Susana Widicus Weaver (Emory Flygare Award University) Shanshan Yu (California Institute of Flygare Award Technology) Gary E. Douberly (University of Georgia) Coblentz Award
The week began with a captivating presentation by Mitchio Okumura (Caltech), who described the collaborative efforts between his and Jun Ye’s (JILA) groups to study the reaction dynamics of OH•, a key atmospheric oxidant, using timeresolved frequency comb spectroscopy (TRFCS) [Fleisher, A. J.; et al. J. Phys. Chem. Lett. 2014, 5, 2241]. By pumping the cavity with a set of coherent frequency combed pulses, they have enhanced the sensitivity of pulsed mid-infrared cavity ringdown experiments by several orders of magnitude (detecting number densities close to 1013/cc in some cases). The fusion of frequency comb and cavity ring-down spectroscopies has allowed them to increase the resolution of their kinetics measurements to a microsecond time scale (10−20 μs resolution). This new technology has been used to study the evolution of intermediates in the oxidation of CH2O by HOO• to form CH2OHOO• and CO by OH• to form CO2. The latter © 2015 American Chemical Society
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DOI: 10.1021/acs.jpca.5b07385 J. Phys. Chem. A 2015, 119, 9570−9572
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The Journal of Physical Chemistry A
microsolvation and molecular recognition processes. Richard Dawes (Missouri University of Science and Technology) presented a novel approach to the construction of potential energy surfaces using a PES generator program. In addition, he presented a high-level method (GWA-SA-CASSCF/MRCI) for describing electronic structures of molecules for global potential energy surfaces. Susanna L. Widicus Weaver (Emory University) presented a study on the O(1D) insertion reactions with methane, vinyl alcohol, and methylamine using millimeter and submillimeter spectroscopy. She discussed her results in comparison to astronomical observations. Shanshan Yu (Caltech) discussed advances in spectroscopic techniques in support of NASA missions. More specifically, she presented improved frequencies values for the H3O+ ground state high-J transitions and demonstrated how high-precision measurements will be critical for atmospheric observations in the future. The final award presented was the Coblentz Award. This award is presented annually to an outstanding molecular spectroscopist, under the age of 40. The 2015 recipient of this award is Gary E. Douberly (University of Georgia), for his novel applications of superfluid helium droplet spectroscopy. Douberly provided a review of the helium droplet isolation technique, describing several examples in which the method, combined with infrared and Stark spectroscopies, was used to elucidate the structures of atmospherically relevant radicals. He then shared some interesting results on prereactive complexes and transient species relevant in combustion chemistry. Three mini-symposia were organized to provide targeted immersion in topics of immediate scientific relevance and special interest. The program this year featured mini-symposia on accelerator-based spectroscopy, high-precision spectroscopy and spectroscopy in the classroom. The mini-symposium on accelerator-based spectroscopy highlighted research conducted at synchrotron and free electron laser facilities. This symposium was organized and chaired by Jos Oomens (Radboud University, Nijmegan) and Jennifer van Wijngaarden (University of Manitoba). Gert von Helden (Fritz-Haber-Institut der Max-Planck-Gesellschaft) opened Wednesday’s session with his presentation of a clever experiment in which massselected peptides, generated by electrospray ionization, are mobility-selected and picked up by helium nanodroplets in a linear ion trap, enabling interrogation of cold ions by IRMPD spectroscopy using a free electron laser. This approach is both mass and shape specific, thus reducing spectral congestion due to the presence of multiple conformers. Also presenting in the accelerator-based section, Michael MacDonald spoke about opportunities at the Canadian Light Source, taking advantage of the VLS-PGM beamline. He presented results from two stations dedicated to gas-phase spectroscopy. One station includes a dual toroid electrostatic energy analyzer. This instrument measures energy and angular distributions of charged particles, and in some cases, can be used to obtain photoelectron angular distributions in the molecular frame. The second endstation is a Wiley−McLaren time-of-flight mass spectrometer with multihit electronics for recording partial ion yield spectra and multi-ion coincidence spectra. The mini-symposium on high-precision spectroscopy was organized by Michael Heaven (Emory University) and Trevor Sears (Brookhaven National Lab). This symposium covered all aspects of frequency comb generation, metrology, and precision spectroscopy. Wim Ubachs (VU University Amsterdam) delivered the Journal of Molecular Spectroscopy review lecture. The recipient of this award is chosen from the invited speakers
214203]. Chirped-pulse microwave spectroscopy allows for precise structural characterization of jet-cooled molecules as well as the determination of relative abundances of reactive species within an expansion, based on the measurements of well-defined molecular absorption cross sections. However, microwave spectroscopy is much less sensitive than other workhorse techniques used to interrogate reaction dynamics. Thus, the Suits group has undertaken the challenge of increasing the molecular number densities, while maintaining a cold uniform environment. Indeed, they have achieved large volumes at high number densities (1016 cm−3) by combining a stacked piezo valve with a Laval nozzle to produce a collimated flow of cold molecules. Suits discussed several examples in which they have already uncovered new details on reaction dynamics. Furthermore, they are beginning to use this method to study bimolecular reactions (e.g., CN + CH3CCH → CH2CCH + HCN, CH3CCCN + H, or CH2CCHCN + H) [Abeysekera, C.; et al. J. Phys. Chem. Lett. 2015, 6, 1599]. CPUF is poised to become a powerful tool for studying the reaction dynamics of small organic molecules. During Wednesday’s plenary session, various awards were presented to students and young scientists who presented exceptional talks at ISMS 2014. The first awards presented were the Rao Prizes. Named in honor of Prof. K. Narahari Rao, who played an integral role in hosting ISMS for numerous decades, this award was created to encourage continued participation by graduate students. The 2014 recipients of the Rao Prize for exceptional graduate student talks were Grant Buckingham (University of Colorado, Barney Ellison’s group), Kathryn Chew (Yale University, Patrick Vaccarro’s group), and YuHsuan Huang (National Chiao Tung University, Yuan-Pern Lee’s group). In addition to the student awards, the inaugural Miller Prize was awarded this year. This award was created in honor of Prof. Terry A. Miller, who served as chair of ISMS’s steering committee from 1992 to 2013, and is awarded for the best presentation delivered by a recent Ph.D. The 2014 and first recipient of the Miller Prize was Christopher M. Leavitt, for his presentation on the infrared Stark spectroscopy of the OH·· CH3OH complex in superfluid helium droplets [Hernandez, F. J.; et al. J. Phys. Chem. A 2015, 119, 8125]. Leavitt completed his postdoctoral research with Gary E. Douberly at the University of Georgia. His talk provided details on the trapping of the prereactive species, OH• and CH3OH, inside helium nanodroplets and interrogating them with infrared radiation inside of a Stark cell. The rate of reaction between OH• and CH3OH is known to anomalously increase at cold temperatures because of the formation of a stable entrance channel complex from which quantum mechanical tunneling produces CH3O• and H2O. Thus, helium nanodroplets provide an ideal chemical environment to trap and study these reactants under conditions similar to the interstellar medium. The Flygare Award was also presented for the first time this year. This award was created in honor of Prof. Willis H. Flygare, a distinguished professor of chemistry at the University of Illinois from 1961 to 1981. The Flygare Award recognizes the efforts of early career faculty members. This year, four Flygare Awards were presented and each recipient delivered a talk. Emilio J. Cocinero (UPV-EHU) presented his research on high-resolution spectroscopy of carbohydrates. He demonstrated how a combination of microwave and laser techniques can provide insight into the structures, conformations, and properties of monosaccharides, oligosaccharides, and their 9571
DOI: 10.1021/acs.jpca.5b07385 J. Phys. Chem. A 2015, 119, 9570−9572
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The Journal of Physical Chemistry A and is invited to submit the research to the Journal of Molecular Spectroscopy for publication. Wim presented his work on possible variations in the fundamental constants of molecular hydrogen when measured on cosmological time scales. The third mini-symposium, spectroscopy in the classroom, was organized by Stephen Cooke (Purchase College, SUNY) and Andrea Minei (College of Mount St. Vincent). The symposium commenced with an invited lecture from Colin Western (University of Bristol), developer of the widely used simulation program PGOPHER. Colin presented two experiments that utilize the software, as well as various potential modifications to make them appropriate for use at various educational levels. PGOPHER is particularly appealing because it is open source and is available for use on multiple operating systems. Another well-received talk in this mini-symposium was that of Robert Le Roy (University of Waterloo), entitled “Spectroscopy for the Masses”. He outlined a course designed for undergraduates, introducing them to the basic principles of spectroscopy. The 70th International Symposium on Molecular Spectroscopy continued in the tradition of bringing together experimentalists and theoreticians to discuss state-of-the-art techniques for unraveling the structures and microscopic mechanics at play in the molecular size regime. For example, the meeting topics since 1946 have evolved from the first treatments of quantum asymmetric rotors and the new technologies of the “radar era” to microwave chirped pulse and frequency comb spectroscopies [Winnewisser, B. P. J. Mol. Spectrosc. 2011, 269, 2]. From the days of David Dennison and Harald Nielsen, in which quantum mechanics was only 20 years old, some of the molecules have gotten larger and more terms in the Hamiltonians are treatable, but the supportive atmosphere and meticulous planning have remained unchanged. It is important to thank all organizers, both past and present, including Terry A. Miller, who ran the symposium for 21 years and transitioned leadership to Benjamin J. McCall’s team in 2014. The sponsors of the meeting (Army Office of Research, Bristol Instruments, Elsevier/JMS, Ideal Vacuum Products, The Journal of Physical Chemistry A, Newport/Spectra Physics, Quantel, and Virginia Diodes) are also greatly appreciated for their continued support. It is a rewarding experience for all who attend this conference to be “standing on the shoulders of giants” [Isaac Newton] and it will be exciting to witness the future of the conference as it continues to settle into its new home at UIUC.
Andrew F. DeBlase† Jonathan A. Maner‡ Antonio D. Brathwaite*,§
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† Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States ‡ Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States § College of Science and Mathematics, University of the Virgin Islands, St. Thomas, United States Virgin Islands 00802
AUTHOR INFORMATION
Corresponding Author
*A. D. Brathwaite. E-mail:
[email protected]. Notes
The authors declare no competing financial interest. 9572
DOI: 10.1021/acs.jpca.5b07385 J. Phys. Chem. A 2015, 119, 9570−9572
