Ultrafast Electron Microscopy for Chemistry, Biology and Material Science

Abstract

For the past thirty years, intense efforts have been made to record atomic scale movies that reveal the movement of atoms in molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid confined to nano-scale volumes. A combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution is required for such atomic movies. Additional important information can be obtained when the energy of the electron beam transmitted through the sample is measured. The four dimensional (4D) spatially and temporally resolved ultrafast electron microscopy method is made possible by the extremely high detection efficiency that is reached in 4D electron microscopy. Using ultra-short electron bunches for the visualization of biological tissue can also improve the spatial resolution compared to conventional electron microscopes, thereby enabling the study of complex biological samples of relevance to the life sciences. Of particular interest to a broad audience is the possibility to create a video, and in the future, a real atomic movie, using 4D electron tomography. IntroductionSince the 1980s, intense efforts have been made to record an atomic movie showing the movements of atoms within molecules, the fast dynamical processes in biological tissues and cells, and the changes in the structure of a solid in a nano-scale volume [1][2][3]. Such an atomic movie requires a combination of sub-nanometer spatial resolution with picosecond or even femtosecond temporal resolution. The aim of any microscopy is to study the structure, composition, and a variety of physical and chemical characteristics of samples (usually solids) on a very small length scale, with linear dimensions of irregularities that are on the order of micrometers or nanometers. While in most microscopies, photon beams (in optical microscopy) or corpusclar beams (for example in electron microscopy) are used as the probes, tunneling microscopies use a very sharp tip that is scanned across surfaces. Electron microscopy and optical microscopy use light and a focused electron beam for imaging, respectively. Beyond those, other microscopic methods may use ions, protons, positrons, or neutrons, or acoustic or microwave radiation in addition to other, less common, methods [3][4][5][6]. In each of them, the specificity of the interaction of a beam of the particles (or photons) and the molecules or atoms of a sample yield unique and rather useful information about the structure, composition and microscopic inhomogeneities of the sample, and the nature of their intermolecular interactions [3,4,7]. For example, the slow neutrons in neutron microscopy and spectroscopy barely interact with the electrons, but interact strongly with the nuclei of the atoms.There are two main approaches to achieve imaging in classical microscopy: 1) In transmission mode, a large area of the sample is illuminated by a beam of light or particles. Specifically designed lenses project the transmitted beam onto a...

Attosecond control of electron beams at dielectric and absorbing membranes

“…Electron pulses of shortest possible length in time are a key technology for ultrafast electron diffraction and microscopy for visualizing atomic and electronic motion in space and time [75][76][77].…”

Ab InitioCalculation of Molecular Diffraction

“…(3)) with a charge density that includes the nuclear charges. [57][58][59][60] Structural dynamics based on time-resolved elastic x-ray scattering has the potential to advance our experimental and theoretical understanding of how nuclei and electrons move during chemical reactions, and in particular our understanding of photochemical reactions, taking us towards the ultimate goal of de novo design of materials and molecules with specific optical, electric, photochemical or mechanical properties.…”

X-ray diffraction line profile analysis of KBr thin films

“…Single-photon sensitivity, excellent time resolution, low signal to noise ratio and most important, high QE, are some essential criteria for an ideal photocathode based device. A hypothetical photocathode comprising all these qualities would certainly beneficial for the extensive developments of the different physics frontiers, including ultraviolet astronomy [1,3,2], underground search of Weakly Interacting Massive Particles (WIMP) for dark matter experiments [4], multiple electron beam lithography [5], Ultrafast Electron Microscope (UEM) [6], generation of highly instance free electron laser beams [7], gaseous photon detectors [8], scintillation detectors [9], medical imaging [10], positron emission tomography [11] etc.…”