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AI for Particle Physics
Published in Volker Knecht, AI for Physics, 2023
Mario Campanelli, Volker Knecht
Bosons behave according to Bose–Einstein statistics, in which several indistinguishable particles can assume the same state. In contrast, fermions obey the Pauli exclusion principle forbidding identical fermions from occupying the same quantum state simultaneously. This rule is the ultimate reason why ordinary matter occupies volume.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The Fermi level is the energy at which there is a 50% probability of it being occupied by an electron. In an intrinsic semiconductor, the Fermi level is located approximately midway between the conduction and valence bands. When a semiconductor is doped with a donor impurity, this probability increases and therefore the Fermi level shifts upward. On doping with an acceptor impurity, the situation reverses and Fermi level shifts downward.
Electrization of Liquids
Published in Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin, Cavitation and Associated Phenomena, 2021
Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin
All particles, aside from coordinates and momentums, are also characterized by spin—the intrinsic angular momentum. This is a special parameter which cannot be interpreted as the ‘angular momentum of a particle spinning around its own axis’ (Landau and Lifshitz 1977), despite the fact that, for the sake of simplicity, approximately half of non-specialists in quantum mechanics represent the spin exactly like that. Bosons have integer spin; fermions have half-integer spin.
Effects of quantum mechanical identity in particle scattering: experimental observations (and lack thereof)
Published in Journal of the Royal Society of New Zealand, 2021
In the quantum description of systems of particles two categories are encountered: particles with half-integer spin, called fermions, and particles with integer spin, called bosons. The quantum mechanical wave function for a system of identical bosons is required to be symmetric under the permutations of two particles. In contrast, the quantum mechanical wave function for a system of identical fermions is required to be antisymmetric under the permutations of two particles. This is the basis of the Pauli exclusion principle which forbids two identical fermions to occupy the same quantum state and for example accounts for the ordering of electrons into shells in atoms: the electron has spin 1/2 (and is consequently a fermion) with the two possible spin projections (spin-up) and (spin-down) – hence there can be exactly two in the innermost shell.
Oxidation behavior with quantum dots formation from amorphous GaAs thin films
Published in Philosophical Magazine, 2018
Srikanta Palei, Bhaskar Parida, Keunjoo Kim
Figure 8 shows the UPS and IPS spectra of the amorphous GaAs layer on nanotextured Si substrate. After the thermal annealing at 100°C for 30 min to remove surface contamination, The measurement was carried out by spectrometry (MODEL: AXIS Ultra DLD, KRATOS Inc.) using UV source of He I (21.2 eV) in steps of 0.02 eV, and a base pressure of 4 × 10−8 Torr. UPS spectra were used to analyze energy levels of the occupied valence electrons below the Fermi level. From the range of binding energy, the low binding energy region of a red circle portion in Figure 8(a) is magnified to understand the valence band maximum (VBM) of the nanodot from the Fermi level. The magnified UPS spectrum showed the VBM value of 1.58 eV below the Fermi level as shown in Figure 8(b). The Fermi level is the minimum energy level occupied by electrons that are weakly bound to the nucleus of the atom. The He I UV source excites electrons to the vacuum level, to determine the work function of As2O3 (Φ = 21.22 eV (He I [1s-2p]) – 17.19 eV = 4.03 eV) above the Fermi level, thus defining the amount of energy required to remove an electron from the Fermi level, and placing it at a vacuum point at rest just outside the surface.