263 research outputs found
Time-Resolved Ultrafast Transient Polarization Spectroscopy to Investigate Nonlinear Processes and Dynamics in Electronically Excited Molecules on the Femtosecond Time Scale
We report a novel experimental technique to investigate ultrafast dynamics in
photoexcited molecules by probing the third-order nonlinear optical
susceptibility. A non-colinear 3-pulse scheme is developed to probe the
ultrafast dynamics of excited electronic states using the optical Kerr effect
by time-resolved polarization spectroscopy. Optical heterodyne and optical
homodyne detection are demonstrated to measure the third-order nonlinear
optical response for the S1 excited state of liquid nitrobenzene, which is
populated by 2-photon absorption of a 780 nm 35 fs excitation pulse.Comment: 12 pages, 4 figures. Changes from previous version: added panel
labels to figures 3-
Intrinsic Pinning in the High Field C-Phase of UPt_3
We report on the a.c. magnetic response of superconducting UPt_3 in a d.c.
magnetic field. At low fields (H < H^*), the in-phase susceptibility shows a
sharp drop at followed by a gradual decrease with decreasing temperature,
while the out-of-phase component shows a large peak at T_c followed by an
unusual broad peak. As the B-C phase line is crossed (H>H^*), however, both the
in-phase and out-of-phase susceptibilities resemble the zero-field Meissner
curves. We interpret these results in terms of a vortex pinning force which,
while comparatively small in the A/B-phases, becomes large enough to
effectively prevent vortex motion in the C-phase.Comment: Modified discussion, slight changes to figures, accepted in PRB Rapid
Communications. RevTex file, 5 figure
- …