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Martin M.A.,Oregon State University | Perry A.,Oregon State University | Masiello T.,California State University, East Bay | Schwartz K.D.,Oregon State University | And 4 more authors.
Journal of Molecular Spectroscopy | Year: 2010

Infrared spectra of bicyclo[1.1.1]pentane (C 5H 8) have been recorded at a resolution (0.0015 cm -1) sufficient to resolve for the first time individual rovibrational lines. This initial report presents the ground state constants for this molecule determined from the detailed analysis of three of the ten infraredallowed bands, ν14(e′) at 540 cm -1, ν 17 (a″ 2) at 1220 cm -1, ν 18(a″ 2) at 832 cm -1, and a partial analysis of the ν 11(e′) band at 1237 cm -1. The upper states of transitions involving the lowest frequency mode, ν 14(e′), show no evidence of rovibrational perturbations but those for the ν 17 and ν 18 (a″ 2) modes give clear indication of Coriolis coupling to nearby e' levels. Accordingly, ground state constants were determined by use of the combination-difference method for all three bands. The assigned frequencies provided over 3300 consistent ground state difference values, yielding the following constants for the ground state (in units of cm -1): B 0 = 0.2399412(2), D J = 6.024(6) × 10 -8, D JK = -1.930(21) × 10 -8. For the unperturbed ν 14(e′) fundamental, more than 3500 transitions were analyzed and the band origin was found to be at 540.34225(2) cm -1. The numbers in parentheses are the uncertainties (two standard deviations) in the values of the constants. The results are compared with those obtained previously for [1.1.1]propellane and with those computed at the ab initio anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set. © 2010 Elsevier Inc. All rights reserved. Source


Kirkpatrick R.,Oregon State University | Masiello T.,California State University, East Bay | Martin M.,Oregon State University | Nibler J.W.,Oregon State University | And 3 more authors.
Journal of Molecular Spectroscopy | Year: 2012

This paper is a continuation of earlier work in which the high resolution infrared spectrum of [1.1.1]propellane was measured and its k and l structure resolved for the first time. Here we present results from an analysis of more than 16 000 transitions involving three fundamental bands ν10 (E′-A1′),ν11(E′-A1′) , ν14 (A2″-A1′) and two difference bands (ν10-ν18) (E′-E″) and (ν11 - ν18) (E′ - E″). Additional information about ν18 was also obtained from the difference band (ν15 + ν18) - ν18 (E′ - E″) and the binary combination band (ν15 + ν18) (E′- A1′). Through the use of the ground state constants reported in an earlier paper [1], rovibrational constants have been determined for all the vibrational states involved in these bands. The rovibrational parameters for the ν18 (E″) state were obtained from combination-differences and showed no need to include interactions with other states. The ν10 (E′) state analysis was also straight-forward, with only a weak Coriolis interaction with the levels of the ν14(A2″) state. The latter levels are much more affected by a strong Coriolis interaction with the levels of the nearby ν11 (E′) state and also by a small but significant interaction with another state, presumably the ν16 (E″) state, that is not directly observed. Gaussian calculations (B3LYP/cc-pVTZ) computed at the anharmonic level aided the analyses by providing initial values for many of the parameters. These theoretical results generally compare favorably with the final parameter values deduced from the spectral analyses. Finally, evidence was obtained for several level crossings between the rotational levels of the ν11 and ν14 states and, using a weak coupling term corresponding to a Δk = ±5, Δl = ∓1 matrix element, it was possible to find transitions from the ground state that, combined with transitions to the same upper state, give a value of C0 = 0.1936515(4) cm-1. This result, combined with the value of B0 = 0.28755833(14) cm -1 reported earlier [1], yields a value of 1.586277(3) for the length of the novel axial CC bond in propellane. © 2012 Elsevier Inc. All rights reserved. Source


Price J.E.,Oregon State University | Coulterpark K.A.,Oregon State University | Masiello T.,California State University, East Bay | Nibler J.W.,Oregon State University | And 3 more authors.
Journal of Molecular Spectroscopy | Year: 2011

Infrared spectra of spiropentane (C5H8) have been recorded at a resolution (0.002 cm-1) sufficient to resolve for the first time individual rovibrational lines. This initial report presents the ground state rotational constants for this molecule determined from the detailed analysis of the ν16 (b2) parallel band at 993 cm -1. In addition, the determination included more than 2000 ground state combination-differences deduced from partial analyses of four other infrared-allowed bands, the ν24(e) perpendicular band at 780 cm-1 and three (b2) parallel bands at 1540 cm-1 (ν14), 1568 cm-1 (ν5 + ν16), and 2098 cm-1 (ν5 + ν14). In each of the latter four cases, the spectra show complications; in the case of ν24, these complications are due to rotational l-type doublings, and in the case of the parallel bands, the spectral complexities are due to Fermi resonance and Coriolis interactions of the upper states with nearby levels. The unraveling of these is underway but the assignment of many of these transitions permit the confident use of the ground state differences in determining the following constants for the ground state (in units of cm-1): B0 = 0.1394741(1), DJ = 2.461(1) × 10-8, DJK = 8.69(3) × 10 -8. For the unperturbed ν16 fundamental, more than 3000 transitions were fit and the band origin was found to be at 992.53793(3) cm-1. The numbers in parentheses are the uncertainties (two standard deviations) in the value of the last digit of the constants. Surprisingly, the very accurate B0 value measured here is lower than the value (0.1418 cm-1) calculated from an electron diffraction structure, instead of being higher, as expected. Where possible, the rovibrational results are compared with those computed at the anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set. These too suggest that the electron diffraction results are in question. © 2011 Elsevier Inc. All rights reserved. Source


Maki A.,15012 24th Ave. | Weber A.,U.S. National Institute of Standards and Technology | Nibler J.W.,Oregon State University | Masiello T.,California State University, East Bay | And 2 more authors.
Journal of Molecular Spectroscopy | Year: 2010

The region of the infrared-active band of the ν9 CH 2 bending mode [1.1.1]propellane has been recorded at a resolution (0.0025 cm-1) sufficient to distinguish individual rovibrational lines. This region includes the partially overlapping bands ν9 (e′) = 1459 cm-1, 2ν18 (l = 2, E′) = 1430 cm-1, ν6 + ν12 (E′) = 1489 cm -1, and ν4 + ν15 (A2″) = 1518 cm-1. In addition, the difference band ν4 - ν15 (A2″) was observed in the far infrared near 295 cm-1 and analyzed to give good constants for the upper ν4 levels. The close proximities of the four bands in the ν9 region suggest that Coriolis and Fermi resonance couplings could be significant and theoretical band parameters obtained from Gaussian ab initio calculations were helpful in guiding the band analyses. The analyses of all four bands were accomplished, based on our earlier report of ground state constants determined from combination differences involving more than 4000 pairs of transitions from five fundamental and four combination bands. This paper presents the analyses and the determination of the upper state constants of all four bands in the region of the ν9 band. Complications were most evident in the 2ν18 (l = 2, E′) band, which showed significant perturbations due to mixing with the nearby 2ν18 (l = 0, A1′) and ν4 + ν12 (E′) levels which are either infrared inactive as transitions from the ground state, or, in the latter case, too weak to observe. These complications are discussed and a comparison of all molecular constants with those available from the ab initio calculations at the anharmonic level is presented. © 2010 Elsevier Inc. All rights reserved. Source

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