Coherent Diffracting Imaging at the Nanoscale
UV and X-ray Free-electron laser (FEL) radiation possesses unique properties such as coherence, high brilliance and ultrashort duration. FLASH at DESY and LCLS at Stanford are the first facilities in the world offering FEL radiation in the regime of X-ray wavelength. They have recently been joined by SACLA in Japan and FERMI@Elettra in Italy with others under construction in Germany, Switzerland, Korea and China. In addition, short wavelength radiation based on the highharmonic generation (HHG) from intense femtosecond lasers is produced routinely, thus offering an alternative (tabletop size) source with different temporal profile than the FEL radiation for the study of ultrashort processes. The subject of the present project is the study of the influence of the dynamics of the systems of nanoscale size (in the gas or solid phase) on the coherent diffraction imaging (CDI) pattern of UV or soft X-ray single radiation scattered from these nanometre scale entities.
In contrast to traditional Xray crystallography patterns, where a repetitive structure (multiple identical copies of the same object, known as a crystal) is imaged, in the present case, CDI images of a single ultrasmall scale object are made. To date, CDI has applied to various structures such as nanocrystals, yeast cell and even to a human chromosome. An important drawback of this single-object technique is that the X-ray energy deposited into the target causes what is known as radiation damage. In the case of X-ray FEL radiation, this is inevitable consequence of the X-ray irradiation can be counterbalanced by the use of extremely short pulses which yield the CDI pattern before the molecule, nanoparticle, etc. breaks up. For example, one case that can be considered as ideal objects for the present objective are atomic clusters. In the present proposal we’ll formulate the relevant theory and calculate the dynamical response of a nanoscale target by studying the CDI pattern at different times of interaction. On the experimental side, in principle, the same information can be obtained by the use of the pump-probe laser technique, widely spread for time resolved experiments.
|Katravulapally Tejaswi has obtained his bachelors degree from “The LNMIIT” (Jaipur, India) in the field of Electronics and Communication Engineering in 2013. During his third year of engineering, he worked as a summer intern under Dr. Lampros Nikolopoulos at DCU and also published a paper, as a co-author, in CEJP. Later, he joined “Indian Institute of Technology Madras” (IIT Madras, Chennai, India) for his masters and obtained his M.Sc. Physics degree in 2016. He was awarded the IIT’s “Merit Cum Means Scholarship” during the full period of his two year masters. At IIT Madras, his masters thesis was in the field of experimental condensed matter physics, closely related to magnetic refregiration. Recently he was awarded the EXTATIC Erasmus Mundus Joint Doctorate scholarship to pursue his PhD in the field of Theoretical Atomic Physics.|