The electron is a subatomic particle, symbol e− or β−, whose electric charge is negative one elementary charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ħ. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavelength for a given energy.
Electrons play an essential role in numerous physical phenomena, such as electricity, magnetism, chemistry and thermal conductivity, and they also participate in gravitational, electromagnetic and weak interactions. Since an electron has charge, it has a surrounding electric field, and if that electron is moving relative to an observer, said observer will observe it to generate a magnetic field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law. Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications such as tribology or frictional charging, electrolysis, electrochemistry, battery technologies, electronics, welding, cathode ray tubes, photoelectricity, photovoltaic solar panels, electron microscopes, radiation therapy, lasers, gaseous ionization detectors and particle accelerators.
Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms. Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge 'electron' in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897 during the cathode ray tube experiment. Electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere. The antiparticle of the electron is called the positron; it is identical to the electron except that it carries electrical charge of the opposite sign. When an electron collides with a positron, both particles can be annihilated, producing gamma ray photons.
How do you know which binding energy shell to use? In the solution it uses K and L2. Why specifically L2 and not L3 or L1 for example?
And what should I do with the information to omit electrons lower than 20kev? I initially thought that meant to omit the electron binding energies lower than...
This is SAMPLE PROBLEM 25-7 from "Physics" by Resnik, Halliday, and Krane, in the chapter "Electric Field and Coulomb's Law".
After describing the behavior of uniformly charged spherical shells:
follows a sample problem:
The solution to (a) goes to say that the volume inside R/2 is 1/8 of the...
According to Leonard Susskind, i.e. the electron has periodically interactions with the Higgs field condensate, that change the electron alternately to be right-handed an left-handed. At 44:20 in the video he says, that, according to the Dirac theory, the mass of the electron is proportional to...
TL;DR Summary: Find acceleration of electron in dB/dt >0
Hello. Here is a problem that i'm not so sure about:
Inside a solenoid there is a time-dipendent magnetic field B, so we have dB/dt = b (constant).
We want to know the acceleration of an electron:
a) placed in the center of the solenoid...
The problem of bound states of an electron trapped in a dipole field is being studied by Alhaidari and company. (See, for example, https://arxiv.org/ftp/arxiv/papers/0707/0707.3510.pdf). It is not clear to me why the point dipole approximation is used everywhere in such calculations. Can't an...
Hello! If I have a (diatomic for simplicity) molecule containing a nucleus that decays by electron capture, are there any theoretical calculations of how that would behave in practice? For example would the lifetime change? Would the resulting molecule still be bound? For example if I start with...
Specifically, this would be beta plus decay and not electron capture, and assumes an electrically neutral radionuclide. Since beta plus decay is the emission of a positron from the nucleus as a proton transmutes into a neutron, the resulting atom now has 1 less elementary charge than before, but...
How to correctly determine the temperature of electrons in an ion source based on ECR?
Is it possible to use the Saha equation?
##\frac{n_en_i}{n_a}=\frac{g_eg_i}{g_a}*3*10^{21} T^{3/2} e^{-J/T}##
Using the search, I found the McWhirter criterion for the applicability of the formula above:
##n_e...
As in title:
Plugging in the definition is straight forward, I am too lazy to type, I will just quote the book Fetter 1971:
Up to here everything is very straight forward, in particular, since we are working on free electron gas, ##E=\hbar \omega##
However, I have no idea how to arrive...
This is actually a two-part question:
1) According to the Copenhagen Interpretation, atoms have energy bands but there's no explanation of how these bands are derived, or why they only form for protons/antiprotons. Any thoughts?
2) The Copenhagen Interpretation mentions that when an atom's...
In the picture below we have two identical orbitals A and B and the system has left-right symmetry. I use the notation ##|n_{A \uparrow}, n_{A \downarrow},n_{B \uparrow},n_{B \downarrow}>## which for example ##n_{A \uparrow}## indicates the number of spin-up electrons in the orbital A. I would...
I am struggling with how to go about this; in particular, I'm not sure I understand what state is being alluded to when Ballentine says "For an electron that approaches the surface from the interior, with momentum ##\hbar k## in the positive ##x## direction, calculate the probability that it...
I did some research online and found that "When certain elementary particles move through a magnetic field, they are deflected in a manner that suggests they have the properties of little magnets." To explain this phenomenon, physicists invented the concept of spin. So far so good.
What I...
Stationary solutions to the Schrödinger equation factor into a spatial part, e.g. atomic and molecular orbitals, and a temporal part that gives the phase rotation frequency. It is often assumed that adding a constant to the potential leaves the physics unchanged. And clearly, any "spectroscopic"...
Hello,
I've seen in a few books on solid state physics that one can deduce an expression for average K.E.:
$$<\:K.E.>\:=E_c+3/2\:k_B\:T$$
from the following:
$$<\:K.E.>\:=\:\frac{\int \:\left(E-E_c\right)g\left(E\right)f\left(E\right)dE}{\int \:g\left(E\right)f\left(E\right)dE}$$
I can't...
I'm reading through Hohenberg's seminal paper titled: "Inhomogeneous Electron Gas" that help lay the foundation for what we know of as Density Functional Theory (DFT) by proving the existence of a universal functional that exactly matches the ground-state energy of a system with a given...
Since there is only one excited electron, it could come from n=3 to n =1directly or n=3 to n =2 and then n=2 to =1.
Hence, there could be one or two lines depending upon the path taken by electron.
Is this right?
When I try P_rel_e = P_ideal I couldn't get a single number that is close to the given T_Max. It might be that I used the wrong equations but I am not sure. Can anyone give me some guidence on this question?
Schrodinger’s original interpretation of the wavefunction was that it represented a smeared out charge density however this was replaced with Max Born’s probability interpretation. The issue was from what I understand that a charge density would repel and have self interactions as all the charge...
The proton and electron are described by separate wavefunctions.
When they come together in the hydrogen atom are they quantum entangled and have a joint wavefunction.
For part (a) of this problem,
The solution is,
However, why did they need to take the absolute value of the charge? I thought they could keep the original signs as shown below:
Using energy conservation, the electric force dose internal work transferring electric potential energy into...
TL;DR Summary: I have a small nut tied to a string. I take a straw and generate free electrons on it by a handkerchief. Then I thouch the nut with the straw and the nut is to be repulsed by it, because of a transfer of part of its electrons. But it does not happen, the nut is attracted to a...
I have seen many tutorials that provide steps how to transcribe a Feynman diagram into algebra, for instance [here]:
However, I have never seen the final line of the calculation converted into a real number. What are the steps to get from the algebra equations transcribed using the Feynman...
Hi,
I asked this question elsewhere, but I didn't understand the answer. It seems to be easy to understand, but for some reason I'm really confuse.
I'm not sure how to find the average position of an electron and the average separation of an electron and his proton in a hydrogen atom.
To be...
I read something about accelerators using nanotubes. I am a little concerned about the design mentioned in the "High Density with Perpendicular Carbon Nanotubes" part of this paper(https://doi.org/10.3390/photonics8060216). Can wakefield acceleration be done in an electron field? Or maybe I...
As QP says it is uncertain that where you found electron. But its not the same phenomena that one fan blade running so fast that you cant see where the blade is. You can only see the blade on a particular position if you use high resulation camera and its position depend on when you take the...
I have a nanoparticle of cadmium selenide with a diameter d. When it emits a photon with a wavelenght lambda, it happens because an electron jumps from the conduction band to the occupied band across a forbidden band. I can suppose that jump as a jump from a higher energy level (the conduction...
I was reading Feynman's lecture on the double-slit experiment, the attempts to determine which slit an electron passes through.
https://www.feynmanlectures.caltech.edu/III_01.html#Ch1-S6
And the key part is when Feynman says, "Then a terrible thing happens.", about the low optical resolutions...
When a photon is absorbed, electrons move from a lower energy level to a higher energy level, so my answer is a, b, c, and f.
I don't understand why the solution is b, c, d, e. Can electrons in this case move from a higher to lower energy level?
Thank you.
Hello guys, I don't know if this is the right place to ask, so please be kind :/
I have a question regarding the location of an electron that belongs to an atom. A teacher told me that the probability of an electron to be found within its orbital is around 99%.
When I asked about the remaining...
Hi everyone!
I need some help in a specific task.
It´s about this problem:
An excited state of atomic calcium has the electron configuration 1s 2 2s 2 2p6 3s 2 3p6 3d1 4f 1 . (a) Derive all the term symbols (with the appropriate specifications of S, L, and J) for the electron configuration. (b)...
Compact electron accelerator reaches new speeds with nothing but light
https://phys.org/news/2022-09-compact-electron.html
Multi-GeV Electron Bunches from an All-Optical Laser Wakefield Accelerator
Abstract
We present the first demonstration of multi-GeV laser...
Hi,
I am have trouble finding whether or not the topic is possible.
It concerns an electronic dipole.
I am well familiar with the general rules: https://en.wikipedia.org/wiki/Selection_rule
Is it possible for transitions to occur from e.g. ^4P_1/2 and ^4P_2/3, which are both in n=3?
If they...
I can't solve the following exercise:
Assume for a certain non-degenerate semiconductor sampe at T = 300 K an intrinsic carrier concentration ##n_i = 2 \cdot 10^{13} \frac{1}{cm^3}## and the band effective densities of states ##N_C = N_V = 10^{19} \frac{1}{cm^3}##.
1. Determine the electron and...
First Assume the following basic circuit:
I read in many textbooks that the electrons in the circuit are accelerated by the positive voltage and decelerated by the collisions, so the speed is constant.
We also know that the circuit current is I = 10A so the power consumed is P = V * I =...
Not sure if this belongs in Chemistry or Physics.
Even less sure if I understand the selection rules for electron transition correctly; hence this question. So I would be grateful for someone to please correct the following:
Letting n and m be energy levels
An electron that absorbs a photon...
Researchers at the Center of Excellence for Quantum Computation and Communication Technology released a study published by Nature describing a quantum device that models the motion of electrons in Polyacetylene. The device is not a general purpose quantum processor, but the methods they used...
In electron capture, a proton turns into a neutron and a neutrino is emitted. Is (without counting the mass difference between neutron and proton and the mass of the neutrino) the mass of the electron converted into energy in the form of gamma radiation?
If we had a system of ##N## non – interacting electrons than a wavefunction of such a system is a product of one-electron wavefunctions otherwise known as a Hartree product: $$ \Psi(x_1,x_2,...,x_N) = \prod_{n=1}^N \psi(x_n) $$
This means that in such a hypothetical system , it is possible to...
I am having trouble understanding this derivation and need some guidance.
1) I tried solving the algebra from the first equation to the second equation circled in red. Can someone please help with what algebra steps, I cannot solve to the circled solution.
2) What does Ee stand for? Is it...
Hi,
I would like to ask question about atmospheric electron neutrinos.
It is known that atmospheric electron neutrinos originate from the decay of muon in the atmosphere, but we can also calculate that muon with energy more than 10 GeV is able to penetrate about 100 km, so it does not decay and...
Does electron beam in empty space generate magnetic fields around them just as with current in conductor.
If yes, then is it experimentally proven that two parallel electron beam would attract each other.
I am trying to compute the Peebles equation as found here:
I am doing so in Python and the following is my attempt:
However, I'm unable to solve it. Either my solver is not enough, or I have wrongly done the function for calculating the Equation.
# imports
from scipy.optimize import fsolve...
For this problem, Is it as simple as using the probability density function, P = Ψ2 and plugging in the radius value given to me?
So essentially I am just squaring the wave function and plugging in?
I'm trying to figure out the second order extension of the "trick" used on page 92 (https://www.damtp.cam.ac.uk/user/tong/aqm/solid3.pdf) for the calculation of the effective mass matrix ##m^{\star}_{ij} = \hbar^2 (\partial^2 E/ \partial k_i \partial k_j)^{-1}## on page 94. I think for this one...