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Norooz Oliaee J, Dehghany M, Rezaei M, McKellar ARW, Moazzen-Ahmadi N. Five intermolecular vibrations of the CO 2 dimer observed via infrared combination bands. J Chem Phys 2016; 145:174302. [PMID: 27825225 DOI: 10.1063/1.4966146] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The weakly bound van der Waals dimer (CO2)2 has long been of considerable theoretical and experimental interest. Here, we study its low frequency intermolecular vibrations by means of combination bands in the region of the CO2 monomer ν3 fundamental (≈2350 cm-1), which are observed using a tunable infrared laser to probe a pulsed supersonic slit jet expansion. With the help of a recent high level ab initio calculation by Wang, Carrington, and Dawes, four intermolecular frequencies are assigned: the in-plane disrotatory bend (22.26 cm-1); the out-of-plane torsion (23.24 cm-1); twice the disrotatory bend (31.51 cm-1); and the in-plane conrotatory bend (92.25 cm-1). The disrotatory bend and torsion, separated by only 0.98 cm-1, are strongly mixed by Coriolis interactions. The disrotatory bend overtone is well behaved, but the conrotatory bend is highly perturbed and could not be well fitted. The latter perturbations could be due to tunneling effects, which have not previously been observed experimentally for CO2 dimer. A fifth combination band, located 1.3 cm-1 below the conrotatory bend, remains unassigned.
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Rezaei M, Norooz Oliaee J, Moazzen-Ahmadi N, McKellar ARW. Infrared spectra reveal box-like structures for a pentamer and hexamer of mixed carbon dioxide-acetylene clusters. Phys Chem Chem Phys 2016; 18:1381-5. [PMID: 26315679 DOI: 10.1039/c5cp03842a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Except for a few cases like water and carbon dioxide, identification and structural characterization of clusters with more than four monomers is rare. Here, we provide experimental and theoretical evidence for existence of box-like structures for a pentamer and a hexamer of mixed carbon dioxide-acetylene clusters. Two mid-infrared cluster absorption bands are observed in the CO2ν3 band region using a tunable diode laser to probe a pulsed supersonic jet. Each requires the presence of both carbon dioxide and acetylene in the jet, and (from observed rotational spacings) involves clusters containing about 4 to 7 molecules. Structures are predicted for mixed CO2 + C2H2 clusters using a distributed multipole model, and the bands are assigned to a specific pentamer, (CO2)3-(C2H2)2, and hexamer, (CO2)4-(C2H2)2. The hexamer has a box-like structure whose D2d symmetry is supported by observed intensity alternation in the spectrum. The pentamer has a closely related structure which is obtained by removing one CO2 molecule from the hexamer. These are among the largest mixed molecular clusters to be assigned by high-resolution spectroscopy.
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Moazzen-Ahmadi N, McKellar ARW, Fernández B, Farrelly D. The infrared spectrum of the Ne-C2D2 complex. J Chem Phys 2015; 143:204307. [PMID: 26627959 DOI: 10.1063/1.4936359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Infrared spectra of Ne-C2D2 are observed in the region of the ν3 fundamental band (asymmetric C-D stretch, ≈2440 cm(-1)) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Like helium-acetylene, this system lies close to the free rotor limit, making analysis tricky because stronger transitions tend to pile up close to monomer (C2D2) rotation-vibration transitions. Assignments are aided by predicted rotational energies calculated from a published ab initio intermolecular potential energy surface. The analysis extends up to the j = 3←2 band, where j labels C2D2 rotation within the dimer, and is much more complete than the limited infrared assignments previously reported for Ne-C2H2 and Ne-C2HD. Two previous microwave transitions within the j = 1 state of Ne-C2D2 are reassigned. Coriolis model fits to the theoretical levels and to the spectrum are compared. Since the variations observed as a function of C2D2 vibrational excitation are comparable to those noted between theory and experiment, it is evident that more detailed testing of theory will require vibrational averaging over the acetylene intramolecular modes.
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Sheybani-Deloui S, Barclay AJ, Michaelian KH, McKellar ARW, Moazzen-Ahmadi N. Communication: Spectroscopic observation of the O-bonded T-shaped isomer of the CO-CO2 dimer and two of its intermolecular frequencies. J Chem Phys 2015; 143:121101. [DOI: 10.1063/1.4932043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Evangelisti L, Perez C, Seifert NA, Pate BH, Dehghany M, Moazzen-Ahmadi N, McKellar ARW. Theory vs. experiment for molecular clusters: Spectra of OCS trimers and tetramers. J Chem Phys 2015; 142:104309. [PMID: 25770542 DOI: 10.1063/1.4914323] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
All singly substituted (13)C, (18)O, and (34)S isotopomers of the previously known OCS trimer are observed in natural abundance in a broad-band spectrum measured with a chirped-pulse Fourier transform microwave spectrometer. The complete substitution structure thus obtained critically tests (and confirms) the common assumption that monomers tend to retain their free structure in a weakly bound cluster. A new OCS trimer isomer is also observed, and its structure is determined to be barrel-shaped but with the monomers all approximately aligned, in contrast to the original trimer which is barrel-shaped with two monomers aligned and one anti-aligned. An OCS tetramer spectrum is assigned for the first time, and the tetramer structure resembles an original trimer with an OCS monomer added at the end with two sulfur atoms. Infrared spectra observed in the region of the OCS ν1 fundamental (≈2060 cm(-1)) are assigned to the same OCS tetramer, and another infrared band is tentatively assigned to a different tetramer isomer. The experimental results are compared and contrasted with theoretical predictions from the literature and from new cluster calculations which use an accurate OCS pair potential and assume pairwise additivity.
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Moazzen-Ahmadi N, McKellar ARW, Fernández B, Farrelly D. The infrared spectrum of the He-C2D2 complex. J Chem Phys 2015; 142:084312. [PMID: 25725736 DOI: 10.1063/1.4913492] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spectra of the helium-acetylene complex are elusive because this weakly bound system lies close to the free rotor limit. Previously, limited assignments of He-C2D2 transitions in the R(0) region of the ν3 fundamental band (≈2440 cm(-1)) were published. Here, new He-C2D2 infrared spectra of this band are obtained using a tunable optical parametric oscillator laser source to probe a pulsed supersonic slit jet expansion from a cooled nozzle, and the analysis is extended to the weaker and more difficult P(1) and R(1) regions. A term value approach is used to obtain a consistent set of "experimental" energy levels. These are compared directly with calculations using two recently reported ab initio intermolecular potential energy surfaces, which exhibit small but significant differences. Rovibrational energies for the He-C2H2 complex are also calculated using both surfaces. A Coriolis model, useful for predicting spectral intensities, is used to interpret the energy level patterns, and a comparison with the isoelectronic complex He-CO is made.
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Rezaei M, George J, Welbanks L, Moazzen-Ahmadi N. Fundamental and combination bands of CO2–C2H2 and CO2–C2D2 in the mid-infrared region. Mol Phys 2014. [DOI: 10.1080/00268976.2014.909611] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Rezaei M, Michaelian KH, Moazzen-Ahmadi N. New combination bands of N2O-CO2, N2O-OCS, and N2O-N2 complexes in the N2O ν(1) region. J Chem Phys 2014; 140:044332. [PMID: 25669548 DOI: 10.1063/1.4862914] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Spectra of the weakly bound complexes N2O-CO2, N2O-OCS, and N2O-N2 were studied in the region of the ν1 fundamental of N2O (∼2224 cm(-1)) using a tunable quantum cascade laser to probe a pulsed supersonic jet expansion with an effective rotational temperature of about 2.5 K. One new combination band was observed for each complex: a band involving an intermolecular in-plane bending mode for N2O-N2, a band involving the disrotation (in-plane geared bend) for of N2O-CO2, and a band involving the out-of-plane torsional vibration for isomer b of N2O-OCS. Small perturbations were noted for the N2O-OCS band. Because of the absence of theoretical prediction, the nature of the intermolecular bending mode for N2O-N2 has not been identified. The resulting intermolecular frequencies are 34.175(1), 17.107(1), and 22.334(1) cm(-1) for N2O-CO2, N2O-OCS, and N2O-N2, respectively. In addition, the previously known fundamental band of N2O-N2 at 2225.99 cm(-1) was analyzed in improved detail. This band exhibits very weak a-type transitions which were not detected in the first infrared observation of this complex, indicating that N2O-N2 is not exactly T-shaped. That is, the N2O molecular axis is not exactly perpendicular to the a-inertial axis, in agreement with a previous structural determination of this complex by rotational spectroscopy.
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Moazzen-Ahmadi N, McKellar A. Spectroscopy of dimers, trimers and larger clusters of linear molecules. INT REV PHYS CHEM 2013. [DOI: 10.1080/0144235x.2013.813799] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Rezaei M, Michaelian KH, Moazzen-Ahmadi N, McKellar ARW. A New Look at the Infrared Spectrum of the Weakly Bound CO–N2 Complex. J Phys Chem A 2013; 117:13752-8. [DOI: 10.1021/jp407896d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Rezaei M, Norooz Oliaee J, Moazzen-Ahmadi N, McKellar A. Infrared spectrum of the CS2 tetramer: Observation of a structure with D2d symmetry. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.03.074] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Rezaei M, Sheybani-Deloui S, Moazzen-Ahmadi N, Michaelian K, McKellar A. CO Dimer: The Infrared Spectrum Revisited. J Phys Chem A 2013; 117:9612-20. [DOI: 10.1021/jp312337v] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rezaei M, Sheybani-Deloui S, Moazzen-Ahmadi N, Michaelian KH, McKellar ARW. Communication: Spectroscopic evidence for a planar cyclic CO trimer. J Chem Phys 2013; 138:071102. [DOI: 10.1063/1.4793220] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Norooz Oliaee J, Dehghany M, Moazzen-Ahmadi N, McKellar ARW. Fundamental and Torsional Combination Bands of Two Isomers of the OCS–CO2 Complex in the CO2 ν3 Region. J Phys Chem A 2013; 117:9605-11. [PMID: 23323975 DOI: 10.1021/jp312339w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Afshari M, Dehghany M, McKellar ARW, Moazzen-Ahmadi N. New infrared bands of nonpolar OCS dimer and experimental frequencies for two intermolecular modes. J Chem Phys 2012; 137:054304. [DOI: 10.1063/1.4739465] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Rezaei M, Moazzen-Ahmadi N, McKellar A, Fernández B, Farrelly D. Towards an understanding of the helium–acetylene van der Waals complex. Mol Phys 2012. [DOI: 10.1080/00268976.2012.699108] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Oliaee JN, Moazzen-Ahmadi N, McKellar A. New spectroscopic results on acetylene dimers and trimers. Mol Phys 2012. [DOI: 10.1080/00268976.2012.697588] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Rezaei M, Oliaee JN, Moazzen-Ahmadi N, McKellar ARW. Spectroscopic observation of nitrous oxide pentamers. J Chem Phys 2012; 136:224308. [DOI: 10.1063/1.4729157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Rezaei M, Michaelian KH, McKellar ARW, Moazzen-Ahmadi N. Infrared spectra of ethylene clusters: (C2D4)2 and (C2D4)3. Phys Chem Chem Phys 2012; 14:8415-8. [PMID: 22588171 DOI: 10.1039/c2cp40597k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Spectra of ethylene dimers and trimers are studied in the ν(11) fundamental band region of C(2)D(4) (≈2200 cm(-1)) using a tuneable quantum cascade laser to probe a pulsed supersonic slit jet expansion. The dimer spectrum is that of a prolate symmetric top perpendicular band, with a distinctive appearance because the A rotational constant is almost exactly equal to six times the B constant. The analysis supports the previously determined cross-shaped dimer structure with D(2d) symmetry. An ethylene trimer has not previously been observed with rotational resolution. The spectrum is that of an oblate symmetric top parallel band. It leads to a proposed trimer structure which is barrel shaped and has C(3h) or C(3) symmetry, with the ethylene monomer C-C axes approximately aligned along the trimer symmetry axis.
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Rezaei M, Michaelian KH, Moazzen-Ahmadi N. Nonpolar nitrous oxide dimer: Observation of combination bands of (14N2O)2 and (15N2O)2 involving the torsion and antigeared bending modes. J Chem Phys 2012; 136:124308. [DOI: 10.1063/1.3697869] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Rezaei M, McKellar ARW, Moazzen-Ahmadi N. Infrared Spectra of the C2H2-(OCS)2 van der Waals Complex: Observation of a Structure with C2 Symmetry. J Phys Chem A 2011; 115:10416-22. [DOI: 10.1021/jp206398w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Norooz Oliaee J, Dehghany M, McKellar ARW, Moazzen-Ahmadi N. High resolution infrared spectroscopy of carbon dioxide clusters up to (CO2)13. J Chem Phys 2011; 135:044315. [PMID: 21806127 PMCID: PMC3160451 DOI: 10.1063/1.3615543] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 06/30/2011] [Indexed: 11/15/2022] Open
Abstract
Thirteen specific infrared bands in the 2350 cm(-1) region are assigned to carbon dioxide clusters, (CO(2))(N), with N = 6, 7, 9, 10, 11, 12 and 13. The spectra are observed in direct absorption using a tuneable infrared laser to probe a pulsed supersonic jet expansion of a dilute mixture of CO(2) in He carrier gas. Assignments are aided by cluster structure calculations made using two reliable CO(2) intermolecular potential functions. For (CO(2))(6), two highly symmetric isomers are observed, one with S(6) symmetry (probably the more stable form), and the other with S(4) symmetry. (CO(2))(13) is also symmetric (S(6)), but the remaining clusters are asymmetric tops with no symmetry elements. The observed rotational constants tend to be slightly (≈2%) smaller than those from the predicted structures. The bands have increasing vibrational blueshifts with increasing cluster size, similar to those predicted by the resonant dipole-dipole interaction model but significantly larger in magnitude.
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Rezaei M, Norooz Oliaee J, Moazzen-Ahmadi N, McKellar ARW. Spectroscopic observation and structure of CS2 dimer. J Chem Phys 2011; 134:144306. [DOI: 10.1063/1.3578177] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Oliaee JN, Dehghany M, Moazzen-Ahmadi N, McKellar ARW. Nitrous oxide tetramer has two highly symmetric isomers. J Chem Phys 2011; 134:074310. [DOI: 10.1063/1.3555629] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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