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Questions tagged [atomic-physics]

Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change. This includes ions as well as neutral atoms and, unless otherwise stated, for the purposes of this discussion it should be assumed that the term atom includes ions.

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How did J. J. Thomson conclude that the particles present in cathode rays were not ions but are in fact much smaller than the smallest of all atoms?

What evidence did he have to prove that the particles in cathode rays are much smaller than atoms? Did he have the e/m ratio of hydrogen ion in 1897? If yes, where did he get that from?
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Why don't atoms constantly emit electromagnetic radiation?

Consider a hydrogen atom: with one proton (and one neutron) and one electron. We can state that, on average, it is electrically neutral. We model the electron by a quantum wavefunction, and therefore ...
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Photon wave function spontaneous emission

Consider some atom that decays from an $L = 1$ state to an $L = 0$ state, thereby emitting a photon. What would the photon's spatial wave function look like? I myself have considered two options: It ...
Jesse's user avatar
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Why should an electron falling into the nucleus, according to the Maxwell's laws of electrodynamics, destroy the atom?

It is often said in physics and chemistry classes and textbooks that atoms must be unstable when the electron continuously loses energy and finally fall into the nucleus according to classical physics....
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Arbitrary first and second moment for squeezed spin coherent state

Consider a spin coherent state of $N$ spin-$1/2$ atoms polarized in the $+x$-direction, denoted $\lvert \frac{\pi}{2},0 \rangle$. Now, squeeze this state in the $+z$-direction with a one-axis twisting ...
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Is there an actual difference between the scattering and absorption/emission of a photon?

Consider a photon incident upon a atom. Dependent on the electronic makeup of the atom, the frequency of the light, and/or group velocity of incident photon, we might see: Various elastic/inelastic ...
DLRune's user avatar
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How to get the expression with Wigner $6j$-symbol from the double-bar expectation from Wigner-Eckart theorem? [closed]

I am reading through a calculation of matrix element of electric dipole interaction Hamiltonian. $\mu$ is electric dipole moment, $\epsilon$ is the polarization vector. The result should be derived ...
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Why are orbitals are stable even though they have wierd shapes?

I'm curious to know about why are they stable, let's talk about $p$-orbital , $p$-orbital is dumbbell shaped shouldn't electrons just fall into the nucleus because we need a centrifugal force to ...
Aditya Mishra's user avatar
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All about electron transition (QFT) [closed]

I am new to quantum mechanics, the more I explore, the more questions I have, please help me find some answers, as I am unable to get understandable ones. Thank you :) Time taken for electron ...
Farheen's user avatar
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2 answers
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If I rotate a solid object, do the atomic nuclei also rotate?

Or is their orientation unaffected by the atomic electrons?
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Why does oxygen green (S1) emission in aurorae only occur at lower altitudes? [duplicate]

Aurorae have a red color at high altitudes caused by the excitation of atomic oxygen and the subsequent emission at about $630 \,\text{nm}$. This happens at high altitudes because at that height there ...
jack_O'Dim's user avatar
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Radiation reaction in the ground state of an atom [duplicate]

In a typical bound energy eigenstate of an atom the magnitude of the wave function is time independent only phase changes in time. So I expect no radiation reaction force in the ground state. However ...
atilla gurel's user avatar
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Radiation reaction in stationary bound states of atom [closed]

In a typical bound energy eigenstate of an atom, the magnitude of the wavefunction is time-independent; only phase changes in time. So I expect no radiation reaction force in the ground state. However,...
atilla gurel's user avatar
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2 answers
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Can an atom absorb a photon that matches the ionization energy of the atom, without ionizing? What would the resulting orbital state be?

Can an atom absorb a photon that matches the ionization energy of the atom, without ionizing? What would the resulting orbital state be? Let's take as an example atom argon (or hydrogen, if that is ...
Hugh Perkins's user avatar
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We know that the mass of nucleus is lesser than calculated value and it converts into binding energy, from where does the mass goes and converts? [closed]

The mass which is lost is very small and we know we can't divide protons or Neutrons. Then how come mass change is very less. Is proton disintegrated? I'm really confused as a high school student. ...
Aditya Mishra's user avatar
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A better Schrödinger Equation with Relativistic Effects?

When you derive the Schrödinger Equation from the Hamiltonian, you perform the following approximation: $$ E^2 = (pc)^2 + (mc^2)^2 \; \; \; \Rightarrow \; \; \; E = \sqrt{(pc)^2 + (mc^2)^2} $$ $$ E = ...
Álvaro Rodrigo's user avatar
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Why do electrons fill the orbitals instead of lin.combination?

In a multi electron atom we start by filling the states 1s, 2s, 2p etc. For the 2p state, we have 2px,2py,2pz, and we fill each one with an electron. Since the 2p state is degenerate, I do not ...
MTYS's user avatar
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How does the united-atom description work? [closed]

I'd like to know something regarding the united-atom approximation: Consider a homonuclear diatomic molecule e.g. $\mathrm{N}_2$. One can obtain its "equivalent" atom that has a nucleus of ...
Eduardo Kuri's user avatar
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Normal Zeeman effect

In normal Zeeman effect, $\mathbf{L}$ and $\mathbf{S}$ vectors decouple with each other and they precess about $\mathbf{B}$ independently. How $\mathbf{S}$ vectors are cancelled out, whereas $\mathbf{...
Subarnarekha Bhattacharyya's user avatar
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About exchange energy

Electrons of the same spin in degenerate orbitals undergo exchange and make the atom more stable. Why do they release energy during exchange? We can calculate the number of possibilities in which the ...
Rohit P L's user avatar
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AC Stark shift in the non-perturbative regime

I am trying to simulate the following situation. I have a 2 level system, with the energy spacing $\omega_0$. I have a laser, with Rabi frequency $\Omega_1$ and frequency $\omega_1$, which I can scan ...
Alex Marshall's user avatar
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1 answer
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Two values of Rydberg Constant

In my textbook I came across two values of Rydberg Constant: \begin{align} R&= 109\,677\ \mathrm{cm}^{-1} \\ R_h&= 2.18 × 10^{-18}\ \mathrm J \end{align} when we are calculating energy of the ...
Curious Guy's user avatar
6 votes
2 answers
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Scalar QED atoms - will they pass through each other?

Atoms generally do not pass through each other. This is usually attributed to the Pauli exclusion principal between the electrons (see links below). If the electrons and nucleons were switched with ...
Rd Basha's user avatar
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Is energy contained in/transferred by light really discrete or is it continuous? [duplicate]

I don't really understand the wave-particle duality of light.I don't really understand the idea of photon, The idea of photon that is generally taught is that it is a fundamental unit of light with ...
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Most up to date explanation explaining the stability of high spin multiplicity (multiplicity=$2S+1$) states?

https://en.wikipedia.org/wiki/Hund%27s_rules: "However, accurate quantum-mechanical calculations (starting in the 1970s)... singly occupied orbitals are less effectively screened or shielded ...
1 vote
1 answer
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Why would a depletion "layer" form in a PN junction?

I understand that electrons diffuse from the N to the P region due to the concentration difference. This diffusion of electrons creates an electric field opposing further diffusion. What I don't ...
Abdullah Al Jaber's user avatar
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Why ionization energy of oxygen dips moving from nitrogen to oxygen if the total spin decreased?

How does spin-orbit splitting also affect this or anomalous zeeman effect or decrease in spin when you move from Nitrogen to Oxygen? Bad Teacher: The addition of the second electron into an already ...
jkj's user avatar
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1 answer
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What happens after a Photon pass-es through an element without causing any ElectronTransition? e.g. A Cube of Scanadium [closed]

Assuming:- No ElectronTransition ==> Photon passes through the atom. [right?] Longer Version In Words:- If a Photon doesn't have enough energy / has more energy than to trigger a ...
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Decomposition of $(x \pm i y) \, Y_{l m}$ and $z \, Y_{l m}$ on spherical harmonics

Using the various algebraic properties of the associated Legendre polynomials $P_l^m(u)$ and of the spherical harmonics $Y_{l m}(\theta, \varphi)$, I was able to decompose the following expressions, ...
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Hydrogen atom energy: $n$ vs $l$ (QM)

I've come across a problem that states the following: let two (separate) particles be subject to a central potential $V(r)$. Their reduced radial function is depicted in the following image: Which ...
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What exactly happens to the "Unabsorbed" Photons? [duplicate]

Things that you can assume that I am familiar with as a high school student. I know that only Photons/EM-Waves with "Specific" Frequency/Wavelength/Energy has chances/probability to --> ...
REYNEP's user avatar
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1 vote
1 answer
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Atomic force is weaker than nuclear force? A terminology question

I'm reading Megawatts and Megatons and on page 15 came across a statement I don't recognize: The nuclear force acting on a single proton is approximately what is needed to support a mass of a hundred ...
Maury Markowitz's user avatar
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1 answer
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Hydrogen atom in a very strong magnetic field

An atom of hydrogen is placed in a very strong magnetic field. The magnetic moment of the orbit of the electron may either align with the external field or may oppose it. What will happen with the ...
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What happens to a coherent state when it passes through an optical amplifier?

I learned from this article that when a quantum state passes through an optical amplifier based on stimulated emission (e.g., EDFA), the variance of its quadrature becomes: $(\Delta X)^2 = G(\Delta ...
Godfly666's user avatar
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Blue color scattering [duplicate]

I'm trying to understand, in terms of cross sections, why is the sky blue? Intuitively, blue has a smaller wavelength than the rest of the colors so it can "see" the internal structure of ...
MTYS's user avatar
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4 answers
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About Quantum Mechanics at macroscopic level [closed]

I am having a discussion with friends about macroscopic VS microscopic in terms of physical theories, and there are parts I would like to understand better from you guys, who know those things well. ...
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1 answer
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Why are there selection rules in electronic transitions?

Why are there selection rules in electronic transitions? What restricts electrons from making transitions to certain states although it is energetically possible?
Tushar Anand's user avatar
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Energy distribution in atomic collision

A photon of energy 10.2 electron Volt collides with a hydrogen atom in ground state. After a certain time interval of few microseconds another photon of energy 15 electron Volt collides inelastically ...
Nandini's user avatar
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"Blow away detection" to measure atom survival in a tweezer array

I am trying to understand the implementation in the following paper (PHYS. REV. X 12, 021027 (2022)) to present it as a term paper for my undergraduate course. I have a basic undergraduate background ...
Krishna Balaji's user avatar
1 vote
2 answers
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Why do atoms absorb photons? [duplicate]

im studying spectra/spectroscopy in school in my chemistry class, and im having to resort to re-teaching myself the chapter due to my teacher's abilities (or lack thereof) i understand how they absorb ...
hannahmcdonnell's user avatar
2 votes
2 answers
377 views

Dielectric and dipole

When a molecule of a dielectric material is placed in an electric field, the molecule acquires an electric dipole moment. Why?
Sam Tunkaho's user avatar
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0 answers
64 views

From a QED perspective, how is light created and propagated?

Using QED, what happens, exactly, when light is created? Let's say an electron loses energy by dropping to a lower orbital, causing quantum of energy to be "emitted." What is that energy ...
RickNZ's user avatar
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Number of ions in positive corona discharge

In Positive Corona discharge, the positively charged ions move toward the negative electrode. If the positive electrode is a grid of thin wires, and the negative electrode is a flat panel, how do we ...
Akansh Karthik's user avatar
1 vote
1 answer
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Why do we assume that all electrons in an atom are in $m_s$ eigenstates, and that each one is in a simultaneous $m_l$ and $m_s$ eigenstate?

I have already read the following discussions and would like to point out that my question goes in a different direction: If superposition is possible in QM, why do we often assume systems are already ...
UVcatastrophe's user avatar
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Spontaneous emission and coherence

Assume I prepare a linear superposition $\frac{1}{\sqrt{2}}(|g \rangle+|e\rangle)$ between a ground and excited level for a large number of "atoms" (it can by any multilevel system, not ...
Alex Marshall's user avatar
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1 answer
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Experiment for generating electricity from high heated and pressurized gas [closed]

Experiment for generating electricity from high heated and pressurized gas. While playing ball at school, many of us had the experience about feeling the energy from the ball hitting it upon the ...
phuse's user avatar
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8 votes
3 answers
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Why do valence electrons not push each other away?

I asked my physics teacher why two electrons come in pairs and not push each other away as you would expect from negative charges. He said that according to the Pauli exclusion principle, there are a ...
Koen de Jong's user avatar
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1 answer
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What are the effects of intramolecular on intermolecular forces?

I'm wondering if intramolecular forces have an effect on intermolecular ones (the converse is also interesting, but I believe that would lead to too edgy physics, which I'm not looking for here). My ...
Simón Flavio Ibañez's user avatar
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1 answer
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Physical Interpretation of BEC Formation

I have recently worked through a theoretical argument for why Bose-Einstein Condensation occurs. If we are comparing an ensemble of distinguishable versus indistinguishable particles, we can compute ...
Relativisticcucumber's user avatar
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2 answers
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Why is helium in excited state with $S = 1$ more stable than $S = 0$? [closed]

In molecular physics, we were told that helium is more stable with total spin $S = 1$ than $S = 0$, so with $1s^12s^1$. I don't understand why.
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