RG. Vibrational structure/frequencies
Thursday, 20150625, 01:30 PM
Noyes Laboratory 100
SESSION CHAIR: John F. Stanton (University of Florida, Gainesville, FL)



RG01 
Contributed Talk 
15 min 
01:30 PM  01:45 PM 
P1177: ALKYL CH STRETCH VIBRATIONS AS A PROBE OF LOCAL ENVIRONMENT AND STRUCTURE 
EDWIN SIBERT, DANIEL P. TABOR, Department of Chemistry, The Univeristy of Wisconsin, Madison, WI, USA; NATHANAEL M. KIDWELL, JACOB C. DEAN, TIMOTHY S. ZWIER, Department of Chemistry, Purdue University, West Lafayette, IN, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG01 
CLICK TO SHOW HTML
The CH stretch region is a good candidate as a probe of structure and local environment. The functional groups are ubiquitous and their vibration spectra exhibit a surprising sensitivity to molecular structure. In this talk we briefly review our theoretical model Hamiltonian [J. Chem. Phys. 138 064308 (2013)] for describing vibrational spectra associated with the CH stretch of CH_{2} groups and then describe an extension of it to molecules containing methyl and methoxy groups. Results are compared to the infrared spectroscopy of four molecules studied under supersonic expansion cooling in gas phase conditions. The molecules include 1,1diphenylethane, 1,1diphenylpropane, 2methoxyphenol (guaiacol), and 1,3dimethoxy2hydroxybenzene (syringol). The curvilinear localmode Hamiltonian predicts most of the major spectral features considered in this study and provides insights into mode mixing. We conclude by returning to CH_{2} groups and explain both why the CH stretch spectrum of cyclohexane is substantially modified when it forms a complex with an alkali metal and what these spectra tell us about the structure of the complex.


RG02 
Contributed Talk 
15 min 
01:47 PM  02:02 PM 
P1032: COMPUTING THE VIBRATIONAL ENERGIES OF CH_{2}O AND CH_{3}CN WITH PHASESPACED LOCALIZED FUNCTIONS AND AN ITERATIVE EIGENSOLVER 
JAMES BROWN, TUCKER CARRINGTON, Department of Chemistry, Queen's University, Kingston, ON, Canada; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG02 
CLICK TO SHOW HTML
For decades scientists have attempted to use ideas of classical mechanics to choose basis functions for calculating spectra. The hope is that a classicallymotivated basis set will be small because it covers only the dynamically important part of phase space. One popular idea is to use phasespace localized (PSL) basis
functions. Because the overlap matrix, in the matrix eigenvalue problem obtained by using PSL functions with the variational method, is not an identity, it is costly to use iterative methods to solve the matrix eigenvalue problem. Iterative methods are imperative if one wishes to avoid storing matrices which is important for larger molecules. Recently J. Brown and T. Carrington Jr., Phys. Rev. Lett. 114, 058901 (2015).e showed it was possible to circumvent the orthogonality (overlap) problem and use iterative eigensolvers. Here, we present calculated vibrational energies of CH_{2}O and CH_{3}CN using the iterative Arnoldi algorithm and PSL functions, and show that our PSL basis is competitive with other previously used basis sets for these molecules.
Footnotes:
J. Brown and T. Carrington Jr., Phys. Rev. Lett. 114, 058901 (2015).w


RG03 
Contributed Talk 
15 min 
02:04 PM  02:19 PM 
P1017: A MULTILAYER SUMOFPRODUCTS METHOD
FOR COMPUTING VIBRATIONAL SPECTRA WITHOUT STORING
FULLDIMENSIONAL VECTORS OR MATRCIES 
PHILLIP THOMAS, TUCKER CARRINGTON, Department of Chemistry, Queen's University, Kingston, ON, Canada; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG03 
CLICK TO SHOW HTML
By optimizing sumofproducts (SOP) basis functions, it is possible to compute vibrational spectra, using a direct product basis, without storing vectors with as many components as there are product basis functions. These ideas are presented in a recent paper: Leclerc and Carrington, J. Chem. Phys 140 174111 (2014). In that paper, the SOP basis functions are products of factors that depend on a single coordinate. When using factors that depend on one coordinate the number of terms (rank) in the SOP basis functions increases with the size of the molecule and the coupling strength. Using multidimensional factors makes it possible to incorporate some of the coupling into the factors and to calculate spectra of molecules with more than a dozen atoms. We use multidimensional factors that are eigenfunctions of reduceddimension Hamiltonians. These can be constructed, in different ways, by organizing the factors into a multiple layer tree. Each node in a layer of a tree represents eigenfunctions of a reduceddimension Hamiltonian for a group of coordinates. We have done calculations with tensortrain and binary tree structures. Efficiency is significantly enhanced by representing the potential with the same tree structure. The ideas are tested by computing energy levels of a 64D model coupled oscillator Hamiltonian and of CH3CN (12 dimensions) with a realistic potential.


RG04 
Contributed Talk 
15 min 
02:21 PM  02:36 PM 
P996: QUANTUM MONTE CARLO ALGORITHMS FOR DIAGRAMMATIC VIBRATIONAL STRUCTURE CALCULATIONS 
MATTHEW HERMES, SO HIRATA, Department of Chemistry, University of Illinois at UrbanaChampaign, Urbana, IL, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG04 
CLICK TO SHOW HTML
Convergent hierarchies of theories for calculating manybody vibrational ground and excitedstate wave functions, such as MøllerPlesset perturbation theory or coupled cluster theory, tend to rely on matrixalgebraic manipulations of large, highdimensional arrays of anharmonic force constants, tasks which require large amounts of computer storage space and which are very difficult to implement in a parallelscalable fashion. On the other hand, existing quantum Monte Carlo (QMC) methods for vibrational wave functions tend to lack robust techniques for obtaining excitedstate energies, especially for large systems. By exploiting analytical identities for matrix elements of position operators in a harmonic oscillator basis, we have developed stochastic implementations of the sizeextensive vibrational selfconsistent field (MCXVSCF) and sizeextensive vibrational MøllerPlesset secondorder perturbation (MCXVMP2) theories which do not require storing the potential energy surface (PES). The programmable equations of MCXVSCF and MCXVMP2 take the form of a small number of highdimensional integrals evaluated using Metropolis Monte Carlo techniques. The associated integrands require independent evaluations of only the value, not the derivatives, of the PES at many points, a task which is trivial to parallelize. However, unlike existing vibrational QMC methods, MCXVSCF and MCXVMP2 can calculate anharmonic frequencies directly, rather than as a small difference between two noisy total energies, and do not require userselected coordinates or nodal surfaces. MCXVSCF and MCXVMP2 can also directly sample the PES in a given approximation without analytical or gridbased approximations, enabling us to quantify the errors induced by such approximations.


RG05 
Contributed Talk 
15 min 
02:38 PM  02:53 PM 
P1000: DIAGRAMMATIC VIBRATIONAL COUPLEDCLUSTER 
JACOB A FAUCHEAUX, SO HIRATA, Department of Chemistry, University of Illinois at UrbanaChampaign, Urbana, IL, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG05 
CLICK TO SHOW HTML
A diagrammatic vibrational coupledcluster method for calculation of zeropoint energies and an equationofmotion coupledcluster method for calculation of anharmonic vibrational frequencies are developed. The methods, which we refer to as XVCC and EOMXVCC respectively, rely on the sizeextensive vibrational selfconsistient field (XVSCF) method for reference wave functions. The methods retain the efficiency advantages of XVSCF making them suitable for applications to large molecules and solids, while they are numerically shown to accurately predict zeropoint energies and frequencies of small molecules as well. In particular, EOMXVCC is shown to perform well for modes which undergo Fermi resonance where traditional perturbative methods fail. Rules for the systematic generation and interpretation of the XVCC and EOMXVCC diagrams to any order are presented.


RG06 
Contributed Talk 
15 min 
02:55 PM  03:10 PM 
P998: VIBRATIONAL JAHNTELLER EFFECT IN NONDEGENERATE ELECTRONIC STATES 
MAHESH B. DAWADI, BISHNU P THAPALIYA, Department of Chemistry, The University of Akron, Akron, OH, USA; RAM BHATTA, Polymer Science, The University of Akron, Akron, OH, USA; DAVID S. PERRY, Department of Chemistry, The University of Akron, Akron, OH, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG06 
CLICK TO SHOW HTML
The JahnTeller theorem H. A. Jahn, and E. Teller, Proc. R. Soc. Lond. A. 161, 220, (1937).tates that “All nonlinear nuclear configurations are therefore unstable for an orbitally degenerate electronic state.” In 1982, Kellman M. E. Kellman, Chem. Phys. Lett. 87, 171, (1982).ealized that the JahnTeller theorem also applies to nonlinear molecular species in nondegenerate electronic states when there are highfrequency vibrations that are degenerate at a symmetrical reference geometry. When those high frequencies can be considered as adiabatic functions of degenerate lowfrequency coordinates, there is a spontaneous JahnTeller distortion that lifts the degeneracy of the highfrequency vibrations. Kellman applied the vibrational JahnTeller (vJT) concept to the Van der Waals dimer (SF _{6}) _{2}.
In this talk, the vJT concept is applied to E ⊗ e systems that are small bound molecules in nondegenerate electronic states. The first case considered in systems for which the global minimum of the electronic potential has C _{3v} symmetry.For such systems, including (C _{6}H _{6})Cr(CO) _{3} and CH _{3}CN, the vJT effect leads to a significant splitting of the degenerate highfrequency vibrations (CH or CO stretches), but the spontaneous vJT distortion is exceptionally small. The second case in systems for which the global minimum of the electronic potential is substantially distorted from the C _{3v} reference geometry. For the second case systems, including CH _{3}OH and CH _{3}SH, the vJT splitting of the degenerate CH stretches is much larger, on the order of several 10Äôs of cm ^{−1}). For both cases, there is the symmetryrequired vibrational conical intersection at the C _{3v} reference geometry. For the second case systems, there are additional symmetryallowed vibrational conical intersections far from the C _{3v} geometry but energetically accessible to the molecule at thermal energies. For both cases, the vibrationally adiabatic surfaces, including the multiple conical intersections, are well described by modest extensions to a highorder Hamiltonian that was developed for the electronic JahnTeller problem. A. Viel, and W. Eisfeld, J. Chem. Phys. 120, 4603, (2004).html:<hr /><h3>Footnotes:
H. A. Jahn, and E. Teller, Proc. R. Soc. Lond. A. 161, 220, (1937).s
M. E. Kellman, Chem. Phys. Lett. 87, 171, (1982).r
A. Viel, and W. Eisfeld, J. Chem. Phys. 120, 4603, (2004).


RG07 
Contributed Talk 
15 min 
03:12 PM  03:27 PM 
P809: IMPACT OF COMPLEXVALUED ENERGY FUNCTION SINGULARITIES ON THE BEHAVIOUR OF RAYLEIGHSCHRÖDINGER PERTURBATION SERIES. H_{2}CO MOLECULE VIBRATIONAL ENERGY SPECTRUM. 
ANDREY DUCHKO, ALEXANDR BYKOV, Molecular Spectroscopy, V.E. Zuev Institute of Atmospheric Optics, Tomsk, Russia; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG07 
CLICK TO SHOW HTML
Nowadays the task of spectra processing is as relevant as ever in molecular spectroscopy. Nevertheless, existing techniques of vibrational energy levels and wave functions computation often come to a deadlock. Application of standard quantummechanical approaches often faces inextricable difficulties. Variational method requires unimaginable computational performance. On the other hand perturbational approaches beat against divergent series. That’s why this problem faces an urgent need in application of specific resummation techniques.
In this research Rayleigh–Schrödinger perturbation theory is applied to vibrational energy levels calculation of excited vibrational states of H_{2}CO. It is known that perturbation series diverge in the case of anharmonic resonance coupling between vibrational states [1]. Nevertheless, application of advanced divergent series summation techniques makes it possible to calculate the value of energy with high precision (more than 10 true digits) even for highly excited states of the molecule [2]. For this purposes we have applied several summation techniques based on highorder PadeHermite approximations. Our research shows that series behaviour completely depends on the singularities of complex energy function inside unit circle. That's why choosing an approximation function modelling this singularities allows to calculate the sum of divergent series. Our calculations for formaldehyde molecule show that the efficiency of each summation technique depends on the resonant type.
REFERENCES
1. J. Cizek, V. Spirko, and O. Bludsky, ON THE USE OF DIVERGENT SERIES IN VIBRATIONAL SPECTROSCOPY. TWO AND THREEDIMENSIONAL OSCILLATORS, J. Chem. Phys. 99, 7331 (1993).
2. A. V. Sergeev and D. Z. Goodson, SINGULARITY ANALYSIS OF FOURTHORDER MÖLLERPLESSET PERTURBATION THEORY, J. Chem. Phys. 124, 4111 (2006).





03:29 PM 
INTERMISSION 


RG09 
Contributed Talk 
15 min 
03:58 PM  04:13 PM 
P859: HIGH RESOLUTION INFRARED SPECTRA OF TRIACETYLENE 
KIRSTIN D DONEY, DONGFENG ZHAO, HAROLD LINNARTZ, Leiden Observatory, Laboratory for Astrophysics, Universiteit Leiden, Leiden, Netherlands; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG09 
CLICK TO SHOW HTML
Triacetylene, HC _{6}H, is the longest polyacetylene chain found in space, and is believed to be involved in the formation of longer chain molecules and polycyclic aromatic hydrocarbons (PAHs). However, abundances are expected to be low, and observational confirmation requires knowledge of the gasphase spectra, which up to now has been incomplete with only the weak, low lying bending modes being known. We present new infrared (IR) spectra in the CH stretch region obtained using ultrasensitive and highly precise IR continuous wave cavity ringdown spectroscopy (cwCRDS), combined with supersonic plasma expansions D. Zhao, J. Guss, A. Walsh, H. Linnartz, Chem. Phys. Lett., 565, 132 (2013) The talk reviews the accurate determination of the rotational constants of the asymmetric fundamental mode, ν _{5}, including discussion on the perturber state, and associated hot bands K.D. Doney, D. Zhao, H. Linnartz, in preparation The determined molecular parameters are accurate enough to aid astronomical searches with such facilities as ALMA (Atacama Large Millimeter Array) or the upcoming JWST (James Webb Space Telecscope), which can now probe even trace molecules (abundances of ∼ 10 ^{−6}  10 ^{−10} with respect to H _{2}).
Footnotes:
D. Zhao, J. Guss, A. Walsh, H. Linnartz, Chem. Phys. Lett., 565, 132 (2013).
K.D. Doney, D. Zhao, H. Linnartz, in preparation.


RG10 
Contributed Talk 
15 min 
04:15 PM  04:30 PM 
P995: INFRARED AND ULTRAVIOLET SPECTROSCOPY OF GASPHASE IMIDAZOLIUM AND PYRIDINIUM IONIC LIQUIDS. 
JUSTIN W. YOUNG, RYAN S BOOTH, CHRISTOPHER ANNESLEY, JAIME A. STEARNS, Space Vehicles Directorate, Air Force Research Lab, Kirtland AFB, NM, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG10 
CLICK TO SHOW HTML
Ionic liquids (ILs) are a highly variable and potentially gamechanging class of molecules for a number of Air Force applications such as satellite propulsion, but the complex nature of IL structure and intermolecular interactions makes it difficult to adequately predict structureproperty relationships in order to make new ILbased technology a reality. For example, methylation of imidazolium ionic liquids leads to a substantial increase in viscosity but the underlying physical mechanism is not understood. In addition, the role of hydrogen bonding in ILs, and especially its relationship to macroscopic properties, is a matter of ongoing research. Here we describe the gasphase spectroscopy of a series of imidazolium and pyridiniumbased ILs, using a combination of infrared spectroscopy and density functional theory to establish the intermolecular interactions present in various ILs, to assess how well they are described by theory, and to relate microscopic structure to macroscopic properties.


RG11 
Contributed Talk 
15 min 
04:32 PM  04:47 PM 
P1123: GROUND AND EXCITED STATE ALKYL CH STRETCH IR SPECTRA OF STRAIGHTCHAIN ALKYLBENZENES 
DANIEL M. HEWETT, JOSEPH A. KORN, TIMOTHY S. ZWIER, Department of Chemistry, Purdue University, West Lafayette, IN, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG11 
CLICK TO SHOW HTML
Vibrational spectra of alkanes in the CH stretch region are often complicated by Fermi resonance with the overtone of the CH bends. This complication has made the CH stretch region difficult to use as a spectroscopic tool for assigning structures to experimental infrared spectra. A firstprinciples model accounting for Fermi resonance has been developed by Sibert and coworkers, and has been successfully implemented to predict the CH stretch region of alkyl groups in a variety of settings (both CH_{2} and CH_{3}). We have recorded jetcooled, singleconformation infrared spectra of a series of straight chain alkylbenzenes having chain lengths of two carbons and longer, serving as a foundation for further tests and refinement of the theoretical model. Ground and excited state IR spectra of these alkylbenzenes were acquired using fluorescence dip infrared spectroscopy. A novel approach for taking the excited state spectra that utilizes the gain of a second, infraredinduced fluorescence peak will be discussed and compared to the typical depletion spectra, using ethylbenzene as a prototypical system.


RG12 
Contributed Talk 
15 min 
04:49 PM  05:04 PM 
P1287: ASYMMETRY OF M^{+}(H_{2}O)RG COMPLEXES, (M=V, Nb) REVEALED WITH INFRARED SPECTROSCOPY 
TIMOTHY B WARD, Department of Chemistry, University of Georgia, Athens, GA, USA; EVANGELOS MILIORDOS, SOTIRIS XANTHEAS, Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA; MICHAEL A DUNCAN, Department of Chemistry, University of Georgia, Athens, GA, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG12 
CLICK TO SHOW HTML
M^{+}(H_{2}O)Ar and M^{+}(H_{2}O)Ne clusters (M=V, Nb) were produced in a laser vaporization/pulsed nozzle source. The clusters were then mass selected in a timeofflight mass spectrometer and studied with infrared photodissociation spectroscopy in the OH stretching region. Spectra showed two bands, with the asymmetric band showing ktype rotational structure. Previous work has shown that most metalwater rare gastagged systems adopt C_{2v} geometry and exhibit the wellknown 3:1 ortho:para ratio in the ktype rotational structure in asymmetric stretch band. However these two metals display a pattern that indicates a breaking of the C_{2v} symmetry. Computational work confirms the breaking of C_{2v} symmetry giving an ArM^{+}O angle of 163.7 degrees for V and 172.1 degrees for Nb. In the ground state we obtain rotational constants that match up well with obtained spectra using 166 degrees for V and 175 degrees for Nb.


RG13 
Contributed Talk 
15 min 
05:06 PM  05:21 PM 
P839: INFRARED SPECTROSCOPY OF PROTONATED ACETYLACETONE AND MIXED ACETYLACETONE/WATER CLUSTERS 
DANIEL MAUNEY, JON MANER, Department of Chemistry, University of Georgia, Athens, GA, USA; DAVID C McDONALD, Chemistry, University of Georgia, Athens, GA, USA; MICHAEL A DUNCAN, Department of Chemistry, University of Georgia, Athens, GA, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG13 
CLICK TO SHOW HTML
Acetylacetone (acac) is the simplest of the betadiketones. which have both keto and enol tautomers with multiple protonation sites. We readily produce the protonated forms in the gas phase and the current investigation uses vibrational spectroscopy coupled with argon tagging to determine which protonated isomers are present in clusters of acac and the effects of solvation on the isomers observed.


RG14 
Contributed Talk 
15 min 
05:23 PM  05:38 PM 
P1342: HEAVY ATOM VIBRATIONAL MODES AND LOWENERGY VIBRATIONAL AUTODETACHMENT IN NITROMETHANE ANIONS 
MICHAEL C THOMPSON, JILA and the Department of Chemistry and Biochemistry, University of ColoradoBoulder, Boulder, CO, USA; JOSHUA H BARABAN, Department of Chemistry, University of Colorado, Boulder, CO, USA; JOHN F. STANTON, Department of Chemistry, The University of Texas, Austin, TX, USA; J. MATHIAS WEBER, JILA and the Department of Chemistry and Biochemistry, University of ColoradoBoulder, Boulder, CO, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG14 
CLICK TO SHOW HTML
We use Ar predissociation and vibrational autodetachment below 2100 cm^{−1}to obtain vibrational spectra of the lowenergy modes of nitromethane anion. We interpret the spectra using anharmonic calculations, which reveal strong mode coupling and Fermi resonances. Not surprisingly, the number of evaporated Ar atoms varies with photon energy, and we follow the propensity of evaporating two versus one Ar atoms as photon energy increases. The photodetachment spectrum is discussed in the context of threshold effects and the importance of hot bands.


RG15 
Contributed Talk 
15 min 
05:40 PM  05:55 PM 
P1348: OBSERVATION OF DIPOLEBOUND STATE AND HIGHRESOLUTION PHOTOELECTRON IMAGING OF COLD ACETATE ANIONS 
GUOZHU ZHU, DAOLING HUANG, LAISHENG WANG, Department of Chemistry, Brown University, Providence, RI, USA; 
IDEALS Archive (Abstract PDF / Presentation File) 
DOI: https://dx.doi.org/10.15278/isms.2015.RG15 
CLICK TO SHOW HTML
We report the observation of a dipolebound state and a highresolution photoelectron imaging study of cryogenically cooled acetate anions (CH _{3}COO ^{−}). Both highresolution nonresonant and resonant photoelectron spectra via the dipolebound state of CH _{3}COO ^{−} are obtained. The binding energy of the dipolebound state relative to the detachment threshold is determined to be 53 ±8 cm^{−1}. The electron affinity of the CH_{3}COO• neutral radical is measured accurately as 26 236 ±8 cm^{−1}(3.2528 ± 0.0010 eV) using highresolution photoelectron imaging. This accurate electron affinity is validated by observation of autodetachment from two vibrational levels of the dipolebound state of CH _{3}COO ^{−}. Excitation spectra to the dipolebound states yield rotational profiles, allowing the rotational temperature of the trapped CH _{3}COO ^{−} anions to be evaluated ^{1}.
[1] D. L. Huang, G. Z. Zhu and L. S. Wang, J. Chem. Phys., 2015, 142, 091103

