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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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Calculation K- and L- absorption edge of Yttrium, why do the values deviate significantly from the literature values? Moseley's law

I want to calculate the K- and L- absorption edge of Yttrium I am using Moseley's law: $$E=(Z - \sigma)^2 \cdot 13.6\text{eV} \left( \frac{1}{n_i^2} - \frac{1}{n_f^2} \right)$$ So, in this case: $$E=(...
CherryBlossom1878's user avatar
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How can any object except Plasma emit white light or be a blackbody--it seems contradictory?

How can any physical object absorb and emit white light when all objects are made from atoms and molecules, each of which has its own absorption/emissions spectrum that acts as it's signature “...
LouL's user avatar
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Energy and momentum conservation for photon absorption [duplicate]

As an undergrad physics student, I am pondering on this question. If an (2 level) atom absorbs a single resonant photon, the energy of electronic state increases by $\hbar \omega$. At the same time ...
phein1's user avatar
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Hund's rules in Helium level scheme

If I am not wrong, Hund's rules state that: I) The highest $2S+1$ has the lowest energy. II) For a given $S$, the lowest $L$ has the highest energy. However, I have found in various textbooks the ...
finn.phys's user avatar
3 votes
1 answer
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Energy eigenvalue of hydrogen-like atoms using Laplace-Runge-Lenz vector

I have a basic question about a few calculations involving the quantum mechanical Laplace-Runge-Lenz vector. In classical mechanics there is the Laplace-Runge-Lenz vector, which for a hydrogen-like ...
Jonathan Huang's user avatar
9 votes
2 answers
2k views

Continued calibration of atomic clocks

First off I am not well versed in physics, but as I understand things the second is defined by the ceasium fountain clock which is calibrated as follows How was the first atomic clock calibrated?. Now ...
Emma Harris's user avatar
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Will an electron release energy when it is added into an atom for which electron affinity value is negative (endothermic)?

According to my understanding, when an electron is added into an atom, it emits energy in the form of photons because it is a form of de-excitation or relaxation. This is when electron affinity will ...
SameerTahir's user avatar
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Do lasers with optical isolator or synchrotron radiation sources allow for Rabi cycles?

In Rabi cycle two-level system cyclically transitions between ground and excited state - bringing question where their energy difference goes during these transitions? For transition from ground to ...
Jarek Duda's user avatar
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Extracting electron wave functions from experiments

In nuclear and nucleon physics it’s quite standard to extract electromagnetic form factors – which are the Fourier transforms of charge and current distributions – from elastic electron-nucleon or ...
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In layman’s language what is the difference between stopping potential and work function?

In layman’s language what is the difference between stopping potential and work function? It feels like both the things mean the same thing, if I am wrong please explain the things to me.
User_5117's user avatar
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X-ray absorption edge, accurate theoretical predition possible?

It is well known that in X-ray absorption spectroscopy, the absorption spectrum shows discontinuities at some critical frequencies. Is it possible to predict locations of these jumps theoretically? I ...
poisson's user avatar
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Surely $\rm CO_2$ reflects incoming solar infrared radiation?

Is the greenhouse effect not cancelled out by the $\rm CO_2$ in the atmosphere reflecting solar infrared radiation back into space? It seems logical to me that, if $\rm CO_2$ reflects infrared shifted ...
Eschaton Magazine's user avatar
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Is the total angular momentum $J$ a good quantum number for the Breit intereaction?

I am reformulating this question because the previous one was closed to the to the claim that is a homework question. According to Wikipedia the Breit operator is given by $$ \hat{B}_{i j}=-\frac{1}{2 ...
amilton moreira's user avatar
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What’s the heaviest possible atomic nucleus?

What’s the heaviest theoretically possible atomic nucleus (highest element number) that can possibly be said to “exist”, such that if one single additional nucleon were added it would collapse into a ...
bretlowery's user avatar
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What is the meaning of $\vec{\alpha}(i) \cdot \vec{\alpha}(j)$?

According to Wikipedia the Breit operator is given by $$ \hat{B}_{i j}=-\frac{1}{2 r_{i j}}\left[\vec{\alpha}(i) \cdot \vec{\alpha}(j)+\frac{\left(\vec{\alpha}(i) \cdot \mathbf{r}_{i j}\right)\left(\...
amilton moreira's user avatar
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Why do we stay at the rotating frame when considering an atom and field interaction in the Rabi problem

In the Atom-Field interaction chapter of the Steck Quantum Optics book, he considers a two level atom interacting with an elecromagnetic wave in the dipole approximation. This leads to a 2X2 ...
eli morhayim's user avatar
2 votes
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At which wavelengths do photons behave like X-ray?

Hard X-rays of wavelengths of about an angstrom are very different than regular lights in a way that they can’t be reflected or refracted, which means their refractive index is always close to 1 ...
哲煜黄's user avatar
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Could the scattering of molecules lead to bond compression?

Suppose you were to send a fast moving binary molecule (such as H-H) at another large target atom A such that the molecule is aligned with the direction of its travel towards the target atom. In other ...
EigenDragon16's user avatar
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1 answer
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Why does an atom become positively charged when it shares its lone pair?

Why does an atom become positively charged when it shares its lone pair? In NH3, Nitrogen doesn't get positive charge when forming covalent bond with Hydrogens. But why does it get positive charge ...
Akhilesh G's user avatar
4 votes
1 answer
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About electron radiation frequency in Heisenberg's 1925 paper

In Heisenberg's 1925 article Quantum Theoretical Interpretation of Kinematic and Mechanical Relations, one of the first things he establishes are the form of the frequency functions in (what I assume ...
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Can we relate the dipole force on a two level atom to the AC stark shift it experiences?

Consider a two level atom, with ground state $|g\rangle$ and excited state $|e\rangle$. In the rotating frame, the dynamics of the two level atom interacting with radiation detuned by $\Delta$, and ...
Adrien Amour's user avatar
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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?
Learner's user avatar
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4 answers
190 views

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....
Learner's user avatar
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1 answer
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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 ...
Silly Goose's user avatar
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7 votes
4 answers
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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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1 vote
1 answer
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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
3 votes
2 answers
102 views

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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2 answers
80 views

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
1 vote
1 answer
39 views

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
8 votes
1 answer
2k views

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
3 votes
2 answers
82 views

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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3 votes
1 answer
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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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1 answer
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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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1 answer
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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
8 votes
1 answer
904 views

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
262 views

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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2 votes
1 answer
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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 ...
Seeker's user avatar
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0 answers
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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
50 views

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 votes
1 answer
44 views

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 ...
REYNEP's user avatar
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1 answer
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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, ...
Cham's user avatar
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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 ...
Lagrangiano'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
4 votes
1 answer
108 views

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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