Analysis of high resolution FTIR spectra from synchrotron sources using evolutionary algorithms

Wijngaarden, Jennifer van; Desmond, Durell S.; Meerts, W. Leo

doi:10.1016/j.jms.2015.04.002

Cited by 5 publications

(3 citation statements)

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“…Assigning complicated high-resolution spectra is a major challenge; consequently, high-resolution spectroscopy is also a science (and art) of the quantum number assignment of measured lines. The techniques used evolved much over the years − but the end results is about the same: a high-resolution spectrum of a polyatomic molecule is converted to a list of labeled energies (Figure ). When spectroscopists analyze high-resolution experimental spectra, they traditionally associate the lines with some good and mostly approximate quantum numbers followed by a fitting of the levels via a small number of spectroscopic parameters of a well-designed model Hamiltonian .…”

Section: Structure Of Spectroscopic Networkmentioning

confidence: 99%

Small Molecules—Big Data

2016

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Quantum mechanics builds large-scale graphs (networks): the vertices are the discrete energy levels the quantum system possesses, and the edges are the (quantum-mechanically allowed) transitions. Parts of the complete quantum mechanical networks can be probed experimentally via high-resolution, energy-resolved spectroscopic techniques. The complete rovibronic line list information for a given molecule can only be obtained through sophisticated quantum-chemical computations. Experiments as well as computations yield what we call spectroscopic networks (SN). First-principles SNs of even small, three to five atomic molecules can be huge, qualifying for the big data description. Besides helping to interpret high-resolution spectra, the network-theoretical view offers several ideas for improving the accuracy and robustness of the increasingly important information systems containing line-by-line spectroscopic data. For example, the smallest number of measurements necessary to perform to obtain the complete list of energy levels is given by the minimum-weight spanning tree of the SN and network clustering studies may call attention to "weakest links" of a spectroscopic database. A present-day application of spectroscopic networks is within the MARVEL (Measured Active Rotational-Vibrational Energy Levels) approach, whereby the transitions information on a measured SN is turned into experimental energy levels via a weighted linear least-squares refinement. MARVEL has been used successfully for 15 molecules and allowed to validate most of the transitions measured and come up with energy levels with well-defined and realistic uncertainties. Accurate knowledge of the energy levels with computed transition intensities allows the realistic prediction of spectra under many different circumstances, e.g., for widely different temperatures. Detailed knowledge of the energy level structure of a molecule coming from a MARVEL analysis is important for a considerable number of modeling efforts in chemistry, physics, and engineering.

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Section: Structure Of Spectroscopic Networkmentioning

confidence: 99%

Small Molecules—Big Data

2016

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“…27 In TMS, the barrier to ring planarity (274(2) cm -1 ) 28 is much higher by comparison and the ground state geometry is that of a flexed ring as confirmed by tunnelling splitting in the microwave and rotationally-resolved infrared spectrum. [28][29][30][31] As the ring backbone is puckered, the lone pairs on sulfur, which are oriented axially or equatorially to the ring, provide two potential binding sites for the partner molecule. This has been confirmed via the rotational spectra of TMS-HF 32 and TMS-HCl 33 which contain signatures due to two separate isomers.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen bonding networks and cooperativity effects in the aqueous solvation of trimethylene oxide and sulfide rings by microwave spectroscopy and computational chemistry

Silva

Wijngaarden

2021

The Journal of Chemical Physics

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The intermolecular interactions responsible for the microsolvation of the highly flexible trimethylene oxide (TMO) and trimethylene sulfide (TMS) rings with one and two water (w) molecules were investigated using rotational spectroscopy (8-22 GHz) and quantum chemical calculations. The observed patterns of transitions are consistent with the most stable geometries of the TMO-w, TMO-(w)2 and TMS-w complexes at the B2PLYP-D3(BJ)/aug-cc-pVTZ level and were confirmed using spectra of the 18 O isotopologue. Due to its effectively planar backbone, TMO offers one unique binding site for solvation while water can bind to the puckered TMS ring in either an axial or equatorial site of the heteroatom. In all clusters, the first water molecule binds in the σv symmetry plane of the ring monomer and serves as a hydrogen bond donor to the heteroatom. The second water molecule is predicted to form a cooperative hydrogen bonding network between the three moieties. Secondary C-H … O interactions are a key stabilizing influence in the trimers and also drive the preferred binding site in the TMS clusters with the axial binding site preferred in TMS-w and the equatorial form calculated to be more stable in the dihydrate. Using an energy partition scheme from symmetry-adapted perturbation theory for the O, S and Se containing mono-and dihydrates, the intermolecular interactions are revealed to be mainly electrostatic but the dispersive character of the contacts is enhanced with increasing size of the ring's heteroatom due to the key role of longer-range secondary interactions.

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“…In both cases, the barriers to planarity (274.2(2) cm -1 (TMS) 7 ; 440(3) cm -1 (SCB) 8 ) are considerably higher and give rise to inversion tunnelling features in the microwave and far infrared spectra. 7,[9][10][11][12][13][14] TMO has been the subject of numerous spectroscopic studies in the microwave, 3,4,15,16 millimeterwave, 17 far infrared 5,6,[18][19][20] and infrared regions. [21][22][23][24][25][26][27] These investigations have largely focused on the ground and ring puckering vibrational states.…”

Section: Introductionmentioning

confidence: 99%