History of X-rays and Their Discoveries

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Questions and Answers

When was the first observation of synchrotron radiation made?

24 April 1947 (correct)

1 April 1947

30 January 1946

15 May 1948

What is the relationship between the photon energies produced by modern synchrotrons and the electrons’ relativistic kinetic energy?

Three times larger

Approximately equal

Three to four orders of magnitude smaller (correct)

Twice the size

Which of the following areas does synchrotron radiation NOT help analyze?

Magnetic properties

Thermal properties (correct)

Chemical structures

Geometric arrangements

Which constants are used in the formula relating energy, frequency, and wavelength of radiation?

𝜈, h, c Signup and view all the answers

What is the speed of light in vacuum as stated in the content?

2.9979 × 10^8 m/s Signup and view all the answers

What is the interatomic spacing in the graphene lattice?

1.42 Å Signup and view all the answers

Which of the following densities corresponds to graphene?

3.8 x 10^15 C/cm2 Signup and view all the answers

What does the notation |ΓK| represent in reciprocal space?

1.70 Å-1 Signup and view all the answers

How many inequivalent carbon atoms are present in a graphene lattice pattern?

2 Signup and view all the answers

What is the gap energy (in eV) for the 4H polytype of SiC?

3.27 eV Signup and view all the answers

What is the approximate number of SiC bilayers in a graphene layer?

3 Signup and view all the answers

What is the primary technique used for epitaxial growth of thin films down to a single layer of atoms?

Molecular Beam Epitaxy (MBE) Signup and view all the answers

What is the density value of SiC specified in C/cm2?

1.2 x 10^15 C/cm2 Signup and view all the answers

What is the primary outcome of Compton scattering?

The scattered photon has lower energy. Signup and view all the answers

Which characterizes Thomson scattering?

Elastic scattering of radiation without energy loss. Signup and view all the answers

What does the cross-section measure in the context of photon interaction?

The probability that photons interact with matter. Signup and view all the answers

What is the significance of the attenuation length, ΛP?

It measures how far a beam can travel before reducing to 1/e of its intensity. Signup and view all the answers

What is a necessary condition for Compton scattering to occur?

Photon energy must exceed mec². Signup and view all the answers

What does the absorption coefficient describe?

The exponential drop in intensity of an incident beam passing through a medium Signup and view all the answers

What is a requirement for a final quantum state to be available for photoabsorption?

The final state must be unoccupied before absorption Signup and view all the answers

Which of the following factors does NOT affect the absorption coefficient?

Temperature of the medium Signup and view all the answers

What happens during X-ray fluorescence?

A core-electron is emitted, and an outer-shell electron transitions to fill the gap Signup and view all the answers

What phenomenon is described by the Beer-Lambert law?

The relationship between light absorption and its concentration in a medium Signup and view all the answers

What is the significance of the Rydberg constant in relation to hydrogen atoms?

It indicates the energy of a level n in a hydrogen atom Signup and view all the answers

Which of the following does NOT describe a core-level absorption edge?

It is associated with outer-shell electron transitions Signup and view all the answers

What initiates Auger emission?

Absorption of energy by a photon resulting in electron ejection Signup and view all the answers

Who first detected X-rays?

Wilhelm Röntgen Signup and view all the answers

Which physicists discovered characteristic x-radiation in 1909?

Barkla and Sadler Signup and view all the answers

What was the focus of Henry Moseley's work?

X-ray emission frequencies versus atomic number Signup and view all the answers

Max von Laue received a Nobel Prize in Physics in which year?

1914 Signup and view all the answers

Who were awarded the Nobel Prize in Physics in 1915?

Bragg and Bragg Signup and view all the answers

The x-ray diffraction images of DNA were essential for which scientists' model of DNA?

Watson and Crick Signup and view all the answers

For their work with X-rays and crystal structures, which Nobel Prize was awarded in 1962?

Chemistry Signup and view all the answers

What was the contribution of Dorothy Hodgkin in the field of X-rays?

Molecular modeling of penicillin Signup and view all the answers

Study Notes

X-rays and their History

X-rays are produced when high-speed electrons decelerate rapidly in an evacuated glass tube.
Wilhelm Röntgen first detected X-rays on November 8, 1895, and received the first Nobel Prize in Physics for this discovery in 1901.
Characteristic X-radiation was discovered in 1909 by Barkla and Sadler, who received a Nobel Prize in 1917.
Henry Moseley's work on X-ray emission frequencies versus atomic number was significant.
Max von Laue produced the first X-ray diffraction pattern (copper sulfate), winning the 1914 Nobel Prize in Physics.
W.H. Bragg and W.L. Bragg's work on X-ray diffraction by crystals earned them the 1915 Nobel Prize in Physics.
X-ray diffraction played a crucial role in determining the structure of DNA (Watson, Crick, and Franklin).
Kendrew and Perutz used X-ray diffraction to determine the structures of myoglobin and hemoglobin, receiving the 1962 Nobel Prize in Chemistry.
Dorothy Hodgkin's X-ray diffraction work on penicillin's structure earned her the 1964 Nobel Prize in Chemistry.
Synchrotron radiation was first observed in 1947 at the General Electric Research Laboratory.
Modern synchrotrons produce photon energies significantly smaller than the electrons' relativistic kinetic energy. Synchrotron radiation is used in multidisciplinary research across diverse fields.

Interaction of X-rays with Matter

X-rays interact with matter through electrons, photons, and ions, providing information on chemistry, geometry, electronic structure, and magnetic properties.

The Electromagnetic Spectrum

The energy of a photon (E) is related to its frequency (ν) and wavelength (λ): E = hν = hc/λ, where h is Planck's constant (6.626 × 10⁻³⁴ J s) and c is the speed of light (2.9979 × 10⁸ m/s).
Cross-section measures the probability of photon interaction with matter through a specific process. The attenuation length (ΛP) is the length at which beam intensity reduces to 1/e and depends on atomic number density (Ni).

Compton Scattering

Compton scattering is inelastic scattering where a photon transfers kinetic energy to an electron, resulting in a lower-energy scattered photon. Energy loss and the Compton scattering length are dependent on incident photon energy (hv) relative to electron rest energy (mec²). It's significant for photon energies above 30 keV.

Thomson Scattering

Thomson scattering is elastic scattering of electromagnetic radiation by a free charged particle, meaning photon frequency and particle kinetic energy remain unchanged. The Thomson scattering length and cross-section are defined.

Photoabsorption (X-ray Absorption Process)

Photoabsorption involves photon absorption by an atom, exciting a bound electron to a higher energy level or creating a photoelectron.

Absorption Coefficient

The absorption coefficient describes the exponential decrease in intensity of an X-ray beam passing through matter. It depends on atomic types, distribution, bonding, magnetism, polarization, and wavelength. Examples include beryllium, silicon, and lead.

X-ray Absorption Process

Energy and momentum are conserved during X-ray absorption. Pauli's exclusion principle dictates that the final quantum state must be unoccupied before absorption.

Energy-Level Schemes of Atoms, Molecules, and Solids

The energy of a level (n) in a hydrogen atom is given by: Eₙ = -RH/n², where RH is the Rydberg constant (13.6 eV).
The energy of a photon resonant with a 1s to n transition is calculated accordingly. A large number of electrons (order of Avogadro's number) are involved.

Absorption Edges and Nomenclature

Core-level absorption edges are characteristic absorption features.

X-ray Fluorescence

Characteristic X-ray lines result from outer-shell electron transitions to fill holes created by photoelectron ejection.

Auger Emission

Auger Emission involves the ejection of a core electron, followed by an outer shell electron filling the space, releasing another electron (Auger electron)

Graphene Lattice

Graphene's lattice structure and properties are described including interatomic spacing, pattern, lattice vectors, density, and Brillouin zone dimensions.

SiC Substrates and Graphene Growth

Information about SiC polytypes (3C, 4H, 6H), lattice constants, band gaps, and density is provided. Molecular Beam Epitaxy (MBE) is mentioned as a method of precise thin film growth.

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Description

Explore the fascinating history of X-rays, from Wilhelm Röntgen's groundbreaking discovery in 1895 to the pivotal contributions of Nobel laureates like Bragg and Hodgkin. This quiz will assess your knowledge of significant milestones and innovations in X-ray science. Test your understanding of how X-ray technology has impacted various fields, including chemistry and biology.