Field-induced diastereomers for chiral separation

A novel approach for the state-specific enantiomeric enrichment and the spatial separation of enantiomers is presented. Our scheme utilizes techniques from strong-field laser physics, specifically an optical centrifuge in conjunction with a static electric field, to create a chiral field with defined handedness. Molecular enantiomers experience unique rotational excitation dynamics and this can be exploited to spatially separate the enantiomers using electrostatic deflection. Notably, the rotational-state-specific enantiomeric enhancement and its handedness is fully controllable. To explain these effects, we introduce the conceptual framework of $field\text{-}induced~diastereomers$ of a chiral molecule and perform robust quantum mechanical simulations on the prototypical chiral molecule propylene oxide (C$_3$H$_6$O), for which ensembles with an enantiomeric excess of up to $30~\%$ were obtained

Room temperature line lists for CO2 isotopologues with AB initio computed intensities

We report 13 room temperature line lists for all major CO$_2$ isotopologues, covering 0-8000 \wn. These line lists are a response to the need for line intensities of high, preferably sub-percent, accuracy by remote sensing experiments. Our scheme encompasses nuclear motion calculations supported by critical reliability analysis of the generated line intensities. Rotation-vibration wavefunctions and energy levels are computed using DVR3D and a high quality semi-empirical potential energy surface (PES) [1], followed by computation of intensities using a fully \textit{ab initio} dipole moment surface (DMS). Cross comparison of line lists calculated using pairs of high-quality PES's and DMS's is used to assess imperfections in the PES, which lead to unreliable transition intensities between levels involved in resonance interactions. Four line lists are computed for each isotopologue to quantify sensitivity to minor distortions of the PES/DMS. This provides an estimate of the contribution to the overall line intensity error introduced by the underlying PES. Reliable lines are benchmarked against recent state-of-the-art measurements [2] and HITRAN-2012 supporting the claim that the majority of line intensities for strong bands are predicted with sub-percent accuracy [3]. Accurate line positions are generated using an effective Hamiltonian [4]. We recommend use of these line lists for future remote sensing studies and inclusions in databases. \vspace{15px} \small \renewcommand{\section}[2]{} \begin{thebibliography}{5} \setlength{\parskip}{0pt} \setlength{\itemsep}{0pt plus 0.3ex} \bibitem{12HuScTa.CO2} X.~Huang, D.~W. Schwenke, S.~A. Tashkun, T.~J. Lee, J. Chem. Phys. 136, 124311, 2012. \bibitem{jt613} O. ~L. Polyansky, K. Bielska, M. Ghysels, L. Lodi, N. ~F. Zobov, J. ~T. Hodges, J. Tennyson, PRL, 114, 243001, 2015. \bibitem{jt625} E. Zak, J. Tennyson, O.~L. Polyansky, L. Lodi, S.~A. Tashkun, V.~I. Perevalov, JQSRT, in press and to be submitted. \bibitem{15TaPeGa.CO2} S.~A. Tashkun, V.~I. Perevalov, R.~R. Gamache, J.~Lamouroux, JQSRT, 152, 45--73, 2015. \end{thebibliography

Controlling rotation in the molecular-frame with an optical centrifuge

We computationally demonstrate a new method for coherently controlling the rotation-axis direction in asymmetric top molecules with an optical centrifuge. Appropriately chosen electric-field strengths and the centrifuge's acceleration rate allow to generate a nearly arbitrary rotational wavepacket. For D$_2$S and 2H-imidazole (C$_3$H$_4$N$_2$) we created wavepackets at large values of the rotational quantum number $J$ with the desired projections of the total angular momentum onto two of the molecules' principal axes of inertia. One application of the new method is three-dimensional alignment with a molecular axis aligned along the laser's wave vector, which is important for the three-dimensional imaging of molecules yet not accessible in standard approaches. The simultaneous orientation of the angular momentum in the laboratory frame and in the molecular frame could also be used in robust control of scattering experiments

RAPID-ADIABATIC-PASSAGE CONTROL OF RO-VIBRATIONAL POPULATIONS IN POLYATOMIC MOLECULES

We present a simple method for control of ro-vibrational populations in polyatomic molecules in the presence of inhomogeneous electric fields [1]._x000d_ Cooling and trapping of heavy polar polyatomic molecules has become one of the frontier goals in high-resolution molecular spectroscopy, especially in the context of parity violation measurement in chiral compounds [2]. A key step toward reaching this goal would be development of a robust and efficient protocol for control of populations of ro-vibrational states in polyatomic, often floppy molecules. Here we demonstrate a modification of the stark-chirped rapid-adiabatic-passage technique (SCRAP) [3], designed for achieving high levels of control of ro-vibrational populations over a selected region in space. The new method employs inhomogeneous electric fields to generate space- and time- controlled Stark-shifts of energy levels in molecules. Adiabatic passage between ro-vibrational states is enabled by the pump pulse, which raises the value of the Rabi frequency. _x000d_ This Stark-chirped population transfer can be used in manipulation of population differences between high-field-seeking and low-field-seeking states of molecules in the Stark decelerator [4]. Appropriate timing of voltages on electric rods located along the decelerator combined with a single pump laser renders our method as potentially more efficient than traditional Stark decelerator techniques. Simulations for NH$_3$ show significant improvement in effectiveness of cooling, with respect to the standard 'moving-potential' method [5]. At the same time a high phase-space acceptance of the molecular packet is maintained. _x000d_ _x000d_ {footnotesize_x000d_ begingroup_x000d_ renewcommand{section}[2]{}%_x000d_ %renewcommand{chapter}[2]{}% for other classes_x000d_ begin{thebibliography}{}_x000d_ _x000d_ bibitem{zak17} E.~J. Zak, A. Yachmenev (submitted)._x000d_ bibitem{melanie} C. Medcraft, R. Wolf, M. Schnell, Angew. Chem. Int. Ed., 53, 43, 11656--11659 (2014)_x000d_ bibitem{scrap} M. Oberst, H. Munch, T. Halfman, PRL 99, 173001 (2007)._x000d_ bibitem{kupper} K. Wohlfart, F. Grätz, F. Filsinger, H. Haak, G. Meijer, J. Küpper, Phys. Rev. A 77, 031404(R) (2008)._x000d_ bibitem{bethlem} H. ~L. Bethlem, F. ~M. ~H. Crompvoets, R. ~T. Jongma, S. ~Y. ~T. van de Meerakker, G. Meijer, Phys. Rev. A, 65, 053416 (2002)._x000d_ _x000d_ end{thebibliography}_x000d_ endgroup

DVR3DUV: A SUITE FOR HIGH ACCURACY CALCULATIONS OF RO-VIBRONIC SPECTRA OF TRIATOMIC MOLECUlES

We present a computer code (DVR3DUV) for calculations of high-accuracy ro-vibronic spectra of triatomic molecules. The current implementation is an extension to the DVR3D suite [1], which operates with the exact kinetic energy operator, a single potential energy surface and a single dipole moment surface (ro-vibrational transitions only). _x000d_ The main function of the new code is calculation of transition intensities between different electronic states in the rotational-vibrational resolution. _x000d_ As a case study, two electronic states of SO$_2$ molecule are considered. Ro-vibrational wavefunctions and energy levels for the ground $tilde{X}^1A_1$ state of SO$_2$ are calculated using Ames PES [2], while energy levels and wavefunctions of the $tilde{C}^1B_2$ state are calculated using textit{ab initio} PES (MRCI-F12-AVTZ). _x000d_ Transition intensities are computed using a) Franck-Condon approximation; b) textit{ab initio} dipole moment surface between the two electronic states. Results are compared to the latest theoretical and experimental works. Future applications of the DVR3DUV code will focus on highly accurate electronic spectra for atmospherically important species, such as ozone molecule. _x000d_ _x000d_ {footnotesize_x000d_ begingroup_x000d_ renewcommand{section}[2]{}%_x000d_ %renewcommand{chapter}[2]{}% for other classes_x000d_ begin{thebibliography}{}_x000d_ _x000d_ bibitem{1} J. Tennyson, M ~A. Kostin, P. Barletta, G. J. Harris, O ~L. Polyansky, J. Ramanlal, N. F. Zobov, Computer Physics Communications 163 (2004) 85–116._x000d_ bibitem{2} X. Huang, D. ~W. Schwenke, T. ~J. Lee, J Chem Phys. 2014 ;140(11):11431_x000d_ end{thebibliography}_x000d_ endgroup} _x000d

A NONDIRECT PRODUCT DISCRETE VARIABLE REPRESENTATION-LIKE METHOD FOR CALCULATING VIBRATIONAL SPECTRA OF POLYATOMIC MOLECULES

We present a new method for solving the vibrational Schroedinger equation for polyatomic molecules. It has the following advantages: 1) the size of the matrix eigenvalue problem is the size of the required pruned (nondirect product) polynomial-type basis; 2) it requires solving a regular, and not a generalized, symmetric matrix eigenvalue problem; 3) accurate results are obtained even if quadrature points and weights are not good enough to yield a nearly exact overlap matrix; 4) the potential matrix is diagonal; 5) the matrix-vector products required to compute eigenvalues and eigenvectors can be evaluated by doing sums sequentially, despite the fact that the basis is pruned. To achieve these advantages we use sets of nested Leja points and appropriate Leja quadrature weights and special hierarchical basis functions. Matrix-vector products are inexpensive because transformation matrices between the basis and the grid, and their inverses, are lower triangular. Vibrational energy levels of CH$_2$NH are calculated with the new method. For this purpose a simple harmonic oscillator kinetic energy operator and a quartic force field are used

A room temperature CO2_2 line list with ab initio computed intensities

Atmospheric carbon dioxide concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5% or better. We report a theoretical study providing rotation-vibration line intensities substantially within the required accuracy based on the use of a highly accurate {\it ab initio} dipole moment surface (DMS). The theoretical model developed is used to compute CO$_2$ intensities with uncertainty estimates informed by cross comparing line lists calculated using pairs of potential energy surfaces (PES) and DMS's of similar high quality. This yields lines sensitivities which are utilized in reliability analysis of our results. The final outcome is compared to recent accurate measurements as well as the HITRAN2012 database. Transition frequencies are obtained from effective Hamiltonian calculations to produce a comprehensive line list covering all $^{12}$C$^{16}$O$_2$ transitions below 8000 cm$^{-1}$ and stronger than 10$^{-30}$ cm / molecule at $T=296$~

The nuclear-spin-forbidden rovibrational transitions of water from first principles

The water molecule occurs in two nuclear-spin isomers that differ by the value of the total nuclear spin of the hydrogen atoms, i.e., I = 0 for para-H2O and I = 1 for ortho-H2O. Spectroscopic transitions between rovibrational states of ortho and para water are extremely weak due to the tiny hyperfine nuclear-spin-rotation interaction of only ∼30 kHz and so far were not observed. We report the first comprehensive theoretical investigation of the hyperfine effects and ortho-para transitions in H216O due to nuclear-spin-rotation and spin-spin interactions. We also present the details of our newly developed general variational approach to the simulation of hyperfine effects in polyatomic molecules. Our results for water suggest that the strongest ortho-para transitions with room-temperature intensities on the order of 10−31 cm/molecule are about an order of magnitude larger than previously predicted values and should be detectable in the mid-infrared ν2 and near-infrared 2ν1 + ν2 and ν1 + ν2 + ν3 bands by current spectroscopy experiments