X-ray
Astronomy
This branch of
physics was born in 1962 when Italian–American astronomer Riccardo Giacconi
discovered a cosmic x-ray source in the form of a compact star located in the
constellation of Scorpius. For this discovery Giacconi received the 2002 Nobel
Prize in Physics. X-ray astronomy is a relatively new branch of astronomy
dealing with the study of x-ray emission from celestial objects, such as
neutron stars, pulsars, and black holes. Since the X-rays emitted by celestial
objects have relatively low energies of the order of a few KeV, they cannot
penetrate through the Earth’s atmosphere to reach the surface of the Earth.
Thus, to study these celestial rays, detectors must be taken above the Earth’s
atmosphere. Methods used to achieve this involve mounting x-ray detectors on
rockets, balloons, or satellites. The x-ray detectors used for this purpose are
either special charge-coupled devices (CCDs) or micro calorimeters.
X
– Ray Crystallography
X- ray crystallography is a study of
crystal structures through the use of X-ray diffraction techniques. X-rays are
very suitable for this purpose because their wavelength in the 0.1 Ao
(~ 100KeV) to 1 Ao (~10 KeV) range is of the order of typical
crystalline lattice separations. An X-ray beam striking crystalline
lattice is scattered by the
spatial distribution of atomic electrons and the imaged diffraction pattern
provides information on the atomic or molecular structure of the crystalline
sample. In 1912, Max Von Laue established the wave nature of X rays and
predicted that crystals exhibit diffraction phenomena. Soon, there after
William H. Bragg and William L. Bragg analyzed the crystalline structure of
sodium chloride, derived the Bragg relationship and laid the
foundation for X- ray crystallography.
X
Ray Spectroscopy
X ray spectroscopy is an analytical technique for
determination of elemental composition of solid or liquid sample in many fields
Such as material science, environmental science, geology, biology and forensic
science. The technique is divided into three related categories. The most
common of them is the X-ray absorption spectrometry (also called as X-ray
fluorescence spectrometry). The other two are X-ray photoelectron spectrometry
and auger spectrometry. All three techniques rely on creation of vacancies in
atomic shells of the various elements in the sample under study as well as on
an analysis of the effects that accompany the creation of vacancies.
X-rays
Electromagnetic
radiation emitted by charged particles (usually electrons) in changing atomic
energy levels.
