Since the observation of single-molecule surface-enhanced Raman scattering (SMSERS) in 1997, questions regarding the nature of the electromagnetic hot spots responsible for such observations still persist. For the first time, we employ electron-energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to obtain maps of the localized surface plasmon modes of SMSERS-active nanostructures, which are resolved in both space and energy. Single-molecule character is confirmed by the bianalyte approach using two isotopologues of Rhodamine 6G. Surprisingly, the STEM/EELS plasmon maps do not show any direct signature of an electromagnetic hot spot in the gaps between the nanoparticles. The origins of this observation are explored using a fully three-dimensional electrodynamics simulation of both the electron-energy-loss probability and the near-electric field enhancements. The calculations suggest that electron beam excitation of the hot spot is possible, but only when the electron beam is located outside of the junction region.

Formation of crystals in saturated and undersaturated solutions is studied as a result of intense sound, or shock waves, produced by high intensity focused laser pulses. Many tiny crystals are created immediately throughout the solution by the laser-generated sound waves. The compression waves can be created by focusing within the liquid or onto the walls of a container. This new method allows for the instantaneous formation of many “seed” crystals, which are then available for further impurity-free crystal growth. More importantly, the tiny “baby” crystals can be harvested before complete growth into “adult” crystals can occur. This method is shown to produce enough “baby” crystals to provide a glimpse into the initial stages of crystal growth using modern microscopy techniques such as SEM. By employing this new method, simple salts such as sodium bromate, sodium chloride, sodium chlorate, and tartaric acid were successfully crystallized. This method of crystal growth may also allow for the generation of crystals which have previously not been realized or are otherwise difficult to produce.

This review presents an overview of electron ionization time-of-flight mass spectroscopy (EITOFMS), beginning with its early development to the employment of modern high-resolution electron ionization sources. The EITOFMS is demonstrated to be ideally suited for analytical and basic chemical physics studies. Studies of the formation of positive ions by electron ionization time-of-flight mass spectroscopy have been responsible for many of the known ionization potentials of molecules and radicals, as well as accepted bond dissociation energies for ions and neutral molecules. The application of TOFMS has been particularly important in the area of negative ion physics and chemistry. A wide variety of negative ion properties have been discovered and studied by using these methods including: autodetachment lifetimes, metastable dissociation, Rydberg electron transfer reactions and field detachment, SF(6) Scavenger method for detecting temporary negative ion states, and many others.

A large number of optical phenomena rely on the excitation of localized surface plasmon resonances (LSPR) in metallic nanostructures. Electron-energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) has emerged as a technique capable of mapping plasmonic properties on length scales 100 times smaller than optical wavelengths. While this technique is promising, the connection between electron-driven plasmons, encountered in EELS, and photon-driven plasmons, encountered in plasmonic devices, is not well understood. This Perspective highlights some of the contributions that have been made in correlating optical scattering and STEM/EELS from the exact same nanostructures. The experimental observations are further elucidated by comparison with theoretical calculations obtained from the electron-driven discrete dipole approximation, which provides a method to calculate EEL spectra for nanoparticles of arbitrary shape. Applications of plasmon mapping to the electromagnetic hot-spots encountered in single-molecule surface-enhanced Raman scattering and electron beam induced damage in silver nanocubes are discussed. It is anticipated that the complementarity of both techniques will address issues in fundamental and applied plasmonics going forward.

Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O 2 . The OH − desorption yields increase markedly with exposure to O 2 at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O − , attributable to dissociative electron attachment to trapped O 2 molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O 2 shows that this surprising increase in OH − desorption, at elevated temperatures, arises from the reaction of O 2 with damaged DNA sites. These results thus appear to be a manifestation of the so-called "oxygen fixation" effect, well known in radiobiology.