We have developed a compact, low cost, modular, crossed molecular beam machine. The new apparatus utilizes several technological advancements in molecular beams valves, ion detection, and vacuum pumping to reduce the size, cost, and complexity of a molecular beam apparatus. We apply these simplifications to construct a linear molecular beam machine as well as a crossed-atomic and molecular beam...

A pulsed, 20 kv electron beam is focussed upon a vapor-deposited thermocouple, and the resulting temperature vs. time response is studied. The experimental data show much scatter, but are consistent with the theoretical prediction that the characteristic thermal response time T is proportional to d , where d is the beam diameter at the thermocouple. From these data, for the soft-glass substrate...

In convergent-beam electron diffraction (CBED) a highly convergent electron beam is focussed on to a small (~< 50 nm) area of the sample. Instead of the diffraction spots that are obtained in the back focal plane of the objective lens with parallel illumination in conventional selected-area electron diffraction, CBED produces discs of intensity. The point group can be determined uniquely from t...

background: exposure to ionizing radiation is known to induce oxidative stress followed by damage to critical biomolecules like lipids, proteins and dna through radiolysis of cellular water. since radiation has been widely used as an important tool in therapy of cancer, the detailed investigation regarding the dna damage and repair kinetics would help to predict the radiation sensitivity of cel...

We demonstrate that efficient optical pumping of nuclear spins in semiconductor quantum dots (QDs) can be achieved by resonant pumping of optically forbidden transitions. This process corresponds to one-to-one conversion of a photon absorbed by the dot into a polarized nuclear spin, and also has potential for initialization of hole spin in QDs. We find that by employing this spin-forbidden proc...

Optical pumping of an optically thick atomic vapor typically requires a quenching buffer gas, such as N2, to prevent radiation trapping of unpolarized photons which would depolarize the atoms. We show that optical pumping of a trace contamination of Rb present in K metal results in a 4.5 times higher polarization of K than direct optical pumping of K in the absence of N2. Such spin-exchange pol...

We recently extended our experiments on z-dependent electron-beam microbunching using coherent transition radiation (CTR) into the high-gain, self-amplified spontaneous emission free-electron laser (FEL) regime. The UV-visible FEL at the Advanced Photon Source was operated at 530 nm and 385 nm using the bunchcompressed photocathode gun electron beam, linac, and 21.6 m of undulator length. The l...

OBJECTIVE Since the properties of polymers can be influenced using electron-beam irradiation, the aim of this study was to investigate whether electron-beam post-curing can improve the mechanical properties of experimental denture base polymers. MATERIAL AND METHODS Rectangular specimens of different experimental polymeric blends were electron-beam irradiated (post-cured) with 25 kGy and 200 ...

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quan...