%e present the first realization of a measurement of a "weak value, " a concept recently introduced by Aharonov, Albert, and Vaidman (AAV). Our experiment uses a birefringent crystal to separate the two linear-polarization components of a laser beam by a distance small compared to the laser-beam waist. This "weak measurement" is followed by a strong measurement which translates the centroid of the beam by a distance far larger than the birefringence-induced separation. In addition, we present data corresponding to orthogonal initial and final states, for which the weak value is not defined. This interference eAect may have application in the amplification and detection of weak eff'ects.

A templateless method for the synthesis of polyaniline nanofibers and nanorods is reported which is based on gamma irradiation of aqueous solutions of aniline in the presence of an initiator.

Silica aerogels were patterned with CdS using a photolithographic technique based on local heating with infrared (IR) light. The solvent of silica hydrogels was exchanged with an aqueous solution of the precursors CdNO3 and NH4OH, all precooled to a temperature of 5°C. Half of the bathing solution was then replaced by a thiourea solution. After thiourea diffused into the hydrogels, the samples were exposed to a focused IR beam from a continuous wave, Nd-YAG laser. The precursors reacted in the spots heated by the IR beam to form CdS nanoparticles. We lithographed features with a diameter of about 40μm, which extended inside the monoliths for up to 4mm. Samples were characterized with transmission electron microscopy and optical absorption, photoluminescence, and Raman spectroscopies. Spots illuminated by the IR beam were made up by CdS nanoparticles dispersed in a silica matrix. The CdS nanoparticles had a diameter in the 4–6nm range in samples exposed for 4min to the IR beam, and of up to 100nm in samples exposed for 10min.

Lithium atoms channeled in the nodes of an intense standing-wave radiation field are cooled to near the recoil limit by adiabatically reducing the radiation intensity. The final momentum distribution has a narrow component with a root-mean-squared momentum of 2h k in one dimension,~here A k is the momentum of a radiation-field photon. The data are compared with [3]. In this paper, we report cooling atoms to near the recoil limit in one dimension, using a method that requires only two atomic levels.An atom moving in a near-resonant standing-wave radiation field experiences a periodic, spatially varying potential energy due to the interaction of the induced electric dipole moment of the atom with the field. The atom can experience a force in the standing wave since the gradient of the potential energy may be nonzero. For a radiation field with frequency blue-detuned from resonance (i.e. , frequency greater than the atomic resonance frequency), the atoms will be attracted to the nodes of the standing wave. In this case, atoms whose maximum kinetic energy is less than the depth of the potential may be trapped around the nodes [4]. This In the experiment, shown schematically by Fig. 1, a collimated, thermal beam of lithium atoms is crossed at 90' by an intense, blue-detuned standing wave. The

When exposed to intense light of -580 nm, the ground state of K shifts up in energy, passing through two-photon resonances with Rydberg states and finally crossing the two-photon ionization limit. Using laser pulses of 0.5 to 13 ps duration, we have shown experimentally that ionization occurs for short pulses, but for long pulses the population is diverted into the Rydberg states where some population survives the peak intensity of the pulse, in excellent agreement with a dynamic Floquet model.