Mark D. Marshall

Characterization of the lowest‐lying Π bending state of Ar–HCl by far infrared laser–Stark spectroscopy and molecular beam electric resonance

Far infrared laser–Stark spectroscopy is used to populate an excited vibrational state in the van der Waals molecule, ArHCl, in a molecular beam. Microwave–far infrared double resonance allows the identification of this state as the first excited bending state of Π symmetry. Subsequent radio frequency electric resonance of the vibrationally excited molecule combined with far infrared–radio frequency two photon experiments gives the following spectroscopic constants: ν0−B’=33.9248(7) (cm−1), B’=1695.(20) (MHz), μ=0.265(3) (D), eqQaa=12.(7) (MHz), eqQbb−eqQcc=−73.927(23) (MHz), q1=−49.583(2) (MHz). These constants are compared with theoretical predictions obtained using previously suggested potential energy surfaces and are related to the presence of other nearby vibrational states.

Electric dipole moment and quadrupole hyperfine structure of OC–HCl and OC–DCl

Microwave and radio frequency spectra of the weakly bound complex OC–HCl and two of its isotopes measured in static electric field are reported. The values of the dipole moments and the hyperfine constants determined are This molecular complex is shown to have a significant induced dipole moment which is much larger than elementary electrostatic calculations predict. The ratio of the electric quadrupole coupling constant in the DCl complex to that of free DCl is shown to be the same using either the chlorine or the deuterium, indicating no measurable distortion in the electric field gradient at the deuterium nucleus.

Deuterium nuclear quadrupole coupling constants in vibrationally excited C2HD: Evidence for electron reorganization

The l‐doubling spectra of monodeuteroacetylene have been obtained in the ν4=1 (C–D bend) and ν5=1 (C–H bend) states of the molecule with resolution sufficient to determine the deuterium nuclear quadrupole coupling constants. The spectroscopic constants obtained from the J=1 rotational level are UFRULE2 ν4=1 ν5=1 UFRULE1 eqQDaa (kHz) 207.(6) 221.(2) eqQDbb−eqQD cc (kHz)  −31.(22)   −6.(4) CD (kHz)   −6.(2)   −1.5(3) CH (kHz) ⋅⋅⋅  −20.0(5) μ (D)   0.023 59(11)   0.056 24(3) q (MHz) 133.050 6(9) 105.699 3(1) UFRULE2 These results are interpreted in terms of the electron distribution surrounding the deuterium nucleus and are shown to be inconsistent with the assumption of a cylindrical distribution about the C–D bond axis in these states. This deviation from the symmetry appropriate for the molecule at equilibrium is shown to arise from a distortion in the cross section of the electron distribution that is unaccompanied by changes along the bond axis.

Microwave Spectrum And Molecular Structure Of The Argon-(e)-1-chloro-1,2-difluoroethylene Complex

Previous studies of argon complexes with fluoroethylenes have revealed a preference for a geometry that maximizes the contact of the argon atom with heavy atoms on the fluoroethylene.a We have observed a continuation of this trend when one of the fluorine atoms is replaced by chlorine. The argon-(E)-1-chloro-1,2-difluoroethylene complex provides two competing heavy atom cavities, FCCF and FCCl, and the opportunity to examine whether the number of heavy atoms or the associated increase in polarizability is determinative of structure. The 5.6 – 18.1 GHz chirped-pulse Fourier transform microwave spectrum of this species provides initial assignments and predictions for spectra obtained in a more sensitive and higher precision Balle-Flygare instrument. Transitions for both the Cl and Cl isotopologues are observed and analyzed to provide geometric parameters for this non-planar complex. The spectrum is consistent with the argon atom located in the FCCl cavity, and the structure agrees well with ab initio predictions. Comparisons are made with Ar-1chloro-1-fluoroethylene, (Z)-1-chloro-2-fluoroethylene, and Ar-vinyl chloride.