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Giulio Racah
Giulio (Yoel) Racah ( he, ג'וליו (יואל) רקח; February 9, 1909 – August 28, 1965) was an Italian–Israeli physicist and mathematician. He was Acting President of the Hebrew University of Jerusalem from 1961 to 1962. The crater Racah on the Moon is named after him. Biography Giulio (Yoel) Racah was born in Florence, Italy. He earned his BA from the University of Florence in 1930, and continued his studies at Rome with Enrico Fermi. In 1939, due to application of Anti-Jewish laws in Italy, Racah emigrated to the British Mandate of Palestine. In the 1948 Arab–Israeli War, Racah served as deputy commander of the Israeli forces defending Mount Scopus. Racah died at the age of 56, apparently asphyxiated by gas from a faulty heater while visiting Florence. Academic and scientific career In 1937 Racah was appointed Professor of Physics at the University of Pisa. In 1939, after his move to Palestine, he was appointed Professor of Theoretical Physics at the Hebrew ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Florence
Florence ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilancio demografico anno 2013, datISTAT/ref> Florence was a centre of medieval European trade and finance and one of the wealthiest cities of that era. It is considered by many academics to have been the birthplace of the Renaissance, becoming a major artistic, cultural, commercial, political, economic and financial center. During this time, Florence rose to a position of enormous influence in Italy, Europe, and beyond. Its turbulent political history includes periods of rule by the powerful Medici family and numerous religious and republican revolutions. From 1865 to 1871 the city served as the capital of the Kingdom of Italy (established in 1861). The Florentine dialect forms the base of Standard Italian and it became the language of culture throughout Ital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rector (academia)
A rector (Latin for 'ruler') is a senior official in an educational institution, and can refer to an official in either a university or a secondary school. Outside the English-speaking world the rector is often the most senior official in a university, whilst in the United States the most senior official is often referred to as president and in the United Kingdom and Commonwealth of Nations the most senior official is the chancellor, whose office is primarily ceremonial and titular. The term and office of a rector can be referred to as a rectorate. The title is used widely in universities in EuropeEuropean nations where the word ''rector'' or a cognate thereof (''rektor'', ''recteur'', etc.) is used in referring to university administrators include Albania, Austria, the Benelux, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Germany, Greece, Hungary, Iceland, Italy, Latvia, Malta, Moldova, North Macedonia, Poland, Portugal, Romani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racah Seniority Number
The Racah seniority number (seniority quantum number) \nu was introduced by Giulio Racah for the classification of electrons in an atomic configuration. The "seniority number", in a loosing statement, is quantum number In quantum physics and chemistry, quantum numbers describe values of conserved quantities in the dynamics of a quantum system. Quantum numbers correspond to eigenvalues of operators that commute with the Hamiltonian—quantities that can be kno ... additional to the total angular momentum L and total spin S , which gives the degree of unpaired particles. A spin-independent interaction \hat is assumed with the property : \langle l^2;LM_L, \hat, l^2;LM_L \rangle = g(2l+1)\delta_ , where L is the combined angular momentum, M_L magnetic quantum number, l is electrons' orbital angular momenta, and g is the dimensionless magnetic moment. The equation above shows there is no interaction unless the two electrons' orbital angular momenta are coupled to L = 0. The eig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racah Polynomials
In mathematics, Racah polynomials are orthogonal polynomials named after Giulio Racah, as their orthogonality relations are equivalent to his orthogonality relations for Racah coefficients. The Racah polynomials were first defined by and are given by :p_n(x(x+\gamma+\delta+1)) = _4F_3\left begin -n &n+\alpha+\beta+1&-x&x+\gamma+\delta+1\\ \alpha+1&\gamma+1&\beta+\delta+1\\ \end;1\right Orthogonality :\sum_^N\operatorname_n(x;\alpha,\beta,\gamma,\delta) \operatorname_m(x;\alpha,\beta,\gamma,\delta)\frac \omega_y=h_n\operatorname_, :when \alpha+1=-N, :where \operatorname is the Racah polynomial, :x=y(y+\gamma+\delta+1), :\operatorname_ is the Kronecker delta function and the weight functions are :\omega_y=\frac, :and :h_n=\frac\frac\frac, :(\cdot)_n is the Pochhammer symbol. Rodrigues-type formula :\omega(x;\alpha,\beta,\gamma,\delta)\operatorname_n(\lambda(x);\alpha,\beta,\gamma,\delta)=(\gamma+\delta+1)_n\frac\omega(x;\alpha+n,\beta+n,\gamma+n,\delta), :where \nabla is the backwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racah Parameter
When an atom has more than one electron there will be some electrostatic repulsion between those electrons. The amount of repulsion varies from atom to atom, depending upon the number and spin of the electrons and the orbitals they occupy. The total repulsion can be expressed in terms of three parameters ''A'', ''B'' and ''C'' which are known as the Racah parameters after Giulio Racah, who first described them. They are generally obtained empirically from gas-phase spectroscopic studies of atoms. They are often used in transition-metal chemistry to describe the repulsion energy associated with an electronic term. For example, the interelectronic repulsion of a 3P term is ''A'' + 7''B'', and of a 3F term is ''A'' - 8''B'', and the difference between them is therefore 15''B''. Definition The Racah parameters are defined as \begin A \\ B\\ C\\ \end = \begin 1 & 0 & -49\\ 0 & 1 & -5 \\ 0 & 0 & 35 \\ \end\begin F_0 \\ F_2\\ F_4\\ \end where F_k are Slater integrals \begin F_ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racah W-coefficient
Racah's W-coefficients were introduced by Giulio Racah in 1942. These coefficients have a purely mathematical definition. In physics they are used in calculations involving the quantum mechanical description of angular momentum, for example in atomic theory. The coefficients appear when there are three sources of angular momentum in the problem. For example, consider an atom with one electron in an s orbital and one electron in a p orbital. Each electron has electron spin angular momentum and in addition the p orbital has orbital angular momentum (an s orbital has zero orbital angular momentum). The atom may be described by ''LS'' coupling or by ''jj'' coupling as explained in the article on angular momentum coupling. The transformation between the wave functions that correspond to these two couplings involves a Racah W-coefficient. Apart from a phase factor, Racah's W-coefficients are equal to Wigner's 6-j symbols, so any equation involving Racah's W-coefficients may be rewritte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Israel Prize
The Israel Prize ( he, פרס ישראל; ''pras israél'') is an award bestowed by the State of Israel, and regarded as the state's highest cultural honor. History The Israel Prize is awarded annually, on Israeli Independence Day, in a state ceremony in Jerusalem, in the presence of the President, the Prime Minister, the Speaker of the Knesset (Israel's legislature), and the Supreme Court President. The prize was established in 1953 at the initiative of the Minister of Education Ben-Zion Dinor, who himself went on to win the prize in 1958 and 1973. Awarding the prize The prize is awarded in the following four areas, with the precise subfields changing from year to year in a cycle of 4 to 7 years, except for the last area, which is awarded annually: * the humanities, social sciences, and Jewish studies * life and exact sciences * culture, arts, communication and sports * lifetime achievement and exceptional contribution to the nation (since 1972) The recipients of the prize are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ugo Fano
Ugo Fano (July 28, 1912 – February 13, 2001) was an Italian American physicist, notable for contributions to theoretical physics. Biography Ugo Fano was born into a wealthy Jewish family in Turin, Italy. His father was Gino Fano, a professor of mathematics. University studies Fano earned his doctorate in mathematics at the University of Turin in 1934, under Enrico Persico, with a thesis entitled ''Sul Calcolo dei Termini Spettrali e in Particolare dei Potenziali di Ionizzazione Nella Meccanica Quantistica'' (''On the Quantum Mechanical Calculation Spectral Terms and their Extension to Ionization''). As part of his PhD examination he also made two oral presentations entitled: ''Sulle Funzioni di Due o Più Variabili Complesse'' (''On the functions of two or more complex variables'') and ''Le Onde Elettromagnetiche di Maggi: Le Connessioni Asimmetriche Nella Geometria Non Riemanniana'' (''Maggi electromagnetic waves: asymmetric connections in non-Riemannian geometry''). E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Structure
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across. They are so small that accurately predicting their behavior using classical physics, as if they were tennis balls for example, is not possible due to quantum effects. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, then the atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively – such atoms are called ions. The electrons of an atom are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy Level
A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The term is commonly used for the energy levels of the electrons in atoms, ions, or molecules, which are bound by the electric field of the nucleus, but can also refer to energy levels of nuclei or vibrational or rotational energy levels in molecules. The energy spectrum of a system with such discrete energy levels is said to be quantized. In chemistry and atomic physics, an electron shell, or principal energy level, may be thought of as the orbit of one or more electrons around an atom's nucleus. The closest shell to the nucleus is called the " shell" (also called "K shell"), followed by the " shell" (or "L shell"), then the " shell" (or "M shell"), and so on farther and farther from the nucleus. The shells correspond with the principal quan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroscopy
Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO) In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical structure and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Physics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science. Classical physics, the collection of theories that existed before the advent of quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, but is not sufficient for describing them at small (atomic and subatomic) scales. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale. Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values ( quantization); objects have characteristics of both particles and waves (wave–particle duality); and there are limits to ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
