Microsecond studies of layer motion in a ferroelectric liquid crystal device

Small angle X-ray scattering has been employed to study dynamically the layer motion in a ferroelectric liquid crystal device on application of low electric fields. Microsecond time resolution was achieved and the use of an area detector in the experiment allowed the examination of layer motion in two orthogonal planes. The X-ray data show that during switching the chevron structure adopted by the layers distorts, implying a variation in the chevron angle. A rotation of the layers in the plane of the device is also observed, coincident in time with the change in chevron angle. The motion of the layers takes place on a ten microsecond time scale and the angular rotation of the layers is approximately 1°.     

Resonant two-photon ionization spectroscopy of jet-cooled OsC

The optical spectrum of diatomic OsC has been investigated for the first time, with transitions recorded in the range from 17 390 to 22 990 cm(-1). Six bands were rotationally resolved and analyzed to obtain ground and excited state rotational constants and bond lengths. Spectra for six OsC isotopomers, 192 Os 12C (40.3% natural abundance), 190 Os 12C(26.0%), 189 Os 12C(16.0%), 188 Os 12C(13.1%), 187 Os 12C(1.9%), and 186 Os 12C(1.6%), were recorded and rotationally analyzed. The ground state was found to be X 3 Delta 3, deriving from the 4 delta 3 16 sigma 1 electronic configuration. Four bands were found to originate from the X 3 Delta 3 ground state, giving B 0"=0.533 492(33) cm(-1) and r 0 "=1.672 67(5) A for the 192 Os 12C isotopomer (1 sigma error limits); two of these, the 0-0[19.1]2<--X 3 Delta 3 and 1-0[19.1]2<--X 3 Delta 3 bands, form a vibrational progression with Delta G' 1/2=953.019 cm(-1). The remaining two bands were identified as originating from an Omega"=0 level that remains populated in the supersonic expansion. This level is assigned as the low-lying A 3 Sigma 0+ (-) state, which derives from the 4 delta 2 16 sigma 2 electronic configuration. The OsC molecule differs from the isovalent RuC molecule in having an X 3 Delta 3 ground state, rather than the X 2 delta 4, 1 Sigma+ ground state found in RuC. This difference in electronic structure is due to the relativistic stabilization of the 6s orbital in Os, an effect which favors occupation of the 6s-like 16 sigma orbital. The relativistic stabilization of the 16 sigma orbital also lowers the energy of the 4 delta 2 16 sigma 2, 3 Sigma(-) term, allowing this term to remain populated in the supersonically cooled molecular beam.     

Resonance method of electric-dipole-moment measurements in storage rings

A "resonance method" of measuring the electric dipole moment (EDM) of nuclei in storage rings is described, based on two new ideas: (1) Oscillating particles' velocities in resonance with spin precession, and (2) alternately producing two sub-beams with different betatron tunes--one sub-beam to amplify and thus make it easier to correct ring imperfections that produce false signals imitating EDM signals, and the other to make the EDM measurement.     

Combinatorics of the K-theory of affine Grassmannians

We introduce a family of tableaux that simultaneously generalizes the tableaux used to characterize Grothendieck polynomials and k-Schur functions. We prove that the polynomials drawn from these tableaux are the affine Grothendieck polynomials and k-K-Schur functions – Schubert representatives for the K-theory of affine Grassmannians and their dual in the nil Hecke ring. We prove a number of combinatorial properties including Pieri rules.     

Backscattering of transients by tilted truncated cylindrical shells: time-frequency identification of ray contributions from measurements

Impulse backscattering measurements by a thick-walled finite cylindrical shell are examined in the time-frequency domain to identify and characterize individual ray contributions from generalized Lamb waves excited on the shell. Previous experiments and analysis in the frequency-aspect angle domain [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785-794 (1998)] indicate that large backscattering enhancements occur in the midfrequency region for the shell tilted at large angles. Presently this experimental data is examined in the time-frequency domain for selected angles of incidence. Individual ray contributions are evident and their evolution over aspect angle is discussed. The most prominent contribution is due to the meridional ray of the a0 leaky Lamb wave. This feature distinctly highlights the truncation of the shell and is found over a range of aspect angles spanning 200 degrees for the frequencies examined. Also observed are periodic features corresponding to end-reflected helical waves of the a0-. These scattering features are significantly different from those reported for thin-walled finite cylinders at low frequencies. The present results may be useful for target identification and localization and as a comparison tool for high-frequency computational scattering models.