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Rotational constants and structure of para-difluorobenzene determined by femtosecond Raman coherence spectroscopy: A new transient type.
- Source :
- Journal of Chemical Physics; 2015, Vol. 143 Issue 14, p1-12, 12p, 1 Diagram, 6 Charts, 6 Graphs
- Publication Year :
- 2015
-
Abstract
- Femtosecond Raman rotational coherence spectroscopy (RCS) detected by degenerate four-wave mixing is a background-free method that allows to determine accurate gas-phase rotational constants of non-polar molecules. Raman RCS has so far mostly been applied to the regular coherence patterns of symmetric-top molecules, while its application to nonpolar asymmetric tops has been hampered by the large number of RCS transient types, the resulting variability of the RCS patterns, and the 10<superscript>3</superscript>–10<superscript>4</superscript> times larger computational effort to simulate and fit rotational Raman RCS transients. We present the rotational Raman RCS spectra of the nonpolar asymmetric top 1,4-difluorobenzene (para-difluorobenzene, p-DFB) measured in a pulsed Ar supersonic jet and in a gas cell over delay times up to ∼2.5 ns. p-DFB exhibits rotational Raman transitions with ΔJ = 0, 1, 2 and ΔK = 0, 2, leading to the observation of J −, K −, A −, and C–type transients, as well as a novel transient (S–type) that has not been characterized so far. The jet and gas cell RCS measurements were fully analyzed and yield the ground-state (v = 0) rotational constants A<subscript>0</subscript> = 5637.68(20) MHz, B<subscript>0</subscript> = 1428.23(37) MHz, and C<subscript>0</subscript> = 1138.90(48) MHz (1σ uncertainties). Combining the A<subscript>0</subscript>, B<subscript>0</subscript>, and C<subscript>0</subscript> constants with coupled-cluster with single-, double- and perturbatively corrected triple-excitation calculations using large basis sets allows to determine the semi-experimental equilibrium bond lengths r<subscript>e</subscript>(C<subscript>1</subscript>–C<subscript>2</subscript>) = 1.3849(4) Å, r<subscript>e</subscript>(C<subscript>2</subscript>–C<subscript>3</subscript>) = 1.3917(4) Å, r<subscript>e</subscript>(C–F) = 1.3422(3) Å, and r<subscript>e</subscript>(C<subscript>2</subscript>–H<subscript>2</subscript>) = 1.0791(5) Å. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 143
- Issue :
- 14
- Database :
- Complementary Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 110396674
- Full Text :
- https://doi.org/10.1063/1.4932602