What is Selection rules: Definition and 47 Discussions
In physics and chemistry, a selection rule, or transition rule, formally constrains the possible transitions of a system from one quantum state to another. Selection rules have been derived for electromagnetic transitions in molecules, in atoms, in atomic nuclei, and so on. The selection rules may differ according to the technique used to observe the transition. The selection rule also plays a role in chemical reactions, where some are formally spin-forbidden reactions, that is, reactions where the spin state changes at least once from reactants to products.
In the following, mainly atomic and molecular transitions are considered.
Hello!
I have a question about selection rules and electronic transitions of a diatomic molecule: I can't find a good explanation about that, and there's so much confusion about the right rules to use.
I studied that on Bransden-Joachain's "Physics of atoms and molecules", but there (to whom...
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...
I'm confused by the discussion in section §30 (Parity of a state), page 98 of Landau's QM. The functions ##\psi_u## and ##\psi_g## are odd an even states respectively. If ##f## is a true scalar, then it should remain unchanged by inversion of the co-ordinates. Writing ##q' = -q##, then its...
What orbitals are occupied in a synchrotron, and which selection rules limit charged particles in a synchrotron?
A Schrödinger hydrogen atom is not actually the Bohr atom, but the Bohr theory gives correct energies (but not transition probabilities). Why?
Because in a hydrogen-like atom, 2s...
For simplicity I only take a system of two interacting spin-##1/2## nuclei. If the spins have quantum numbers ##m_1## and ##m_2## respectively when in a certain state, then the energy of that particular state is$$E_{m_1m_2} = m_1 v_{0,1} + m_2 v_{0,2} + m_1 m_2 J_{12}$$where ##v_{0,1}## and...
I'm not very familiar with this topic so I quickly went through some introductory books on nuclear physics and read the chpater about beta decay. What I don't understand looking at this graph is the following:
Why is the direct decay to ground state absolutely forbidden ? If you take a 1st order...
I suppose my question is, since X commutes for H, does this mean that the selection rules are $$<n',l',m'|X|n,l,m>=0$$ unless $$l'=l\pm 1$$ and $$m'=m\pm 1$$, as specified in Shankar?
Two questions, where the 1st is related to previous discussion regarding thes couplings:
The selection rules for LS coupling is quite clear - it's based on calculating the compatible electric dipole matrix element. However, in the case of jj coupling we end up with different selection rules...
Hello, I am newish in group theory so sorry if anything in the following is not entirely correct.
In general, one can anticipate if a matrix element <i|O|j> is zero or not by seeing if O|j> shares any irreducible representation with |i>.
I know how to reduce to IRs the former product but I...
Here is what I understand so far about x-ray energy transitions within an atom: The shells are divided up from lowest to highest as K, L, M, N, O, and so on. The X-ray associated with an electron dropping to a K shell is called K radiation. If the electron drops dropped from a shell directly...
Hello
In evolution, the archetype rule is the "natural selection" rule. Are the other selection rules? (technological selection rules, cultural rules, etc)
Thank you for your time.
Regards,
ORF
Question: For ionization of a homonuclear diatomic, how do the selection rules differ for a nonresonant 2-photon ionization process and a 1-photon ionization process?
Hello.
When I accessed to selection rule page in Wikipedia, I have a difficulty of how to use rules listed there.
I'm now only concering electric dipole transition so column (E1) in the table there will be my only interests. Since I need to know whether transition is possible or not between...
Hello everybody,
since I have to plan an experiment to map the energy-momentum dispersion of a bosonic excitation, I have a question related to the difference between the excitations probed by Inelastic X-ray Scattering (IXS) and Electron Energy Loss Spectroscopy (EELS). Both the techniques are...
Homework Statement
I am trying to calculate the selection rules from 2p to 1s. Above are the three results in (1152)-.(1154). And In the image one also finds the spherical harmonics factors. I can not determine which R and angular parts that give the three 2p waves. Can you show which ones...
On the bottom half of page 249 Cohen-Tannoudji it talks about selection rules in terms of off diagonal elements of the matrix generated by ##\langle \phi _{ n^{ \prime },\tau ^{ \prime } } \mid \hat { B } \mid \phi _{ n,\tau } \rangle##. I thought all off diagonal matrix elements would be...
I've been reading up a bit on semiconductor quantum wells, and came across a selection rule for an infinite quantum well that says that "Δn = n' - n = 0", where n' is the quantum well index of an excited electron state in the conduction band, and n is the index of the valence band state where...
While I am reviewing my undergrad physics for qualifying exam, I became confused about the numerous selection rules.
(1) We have the selection rules for spontaneous emission in a hydrogen atom: Δl=±1 ,Δml=0,±1. This rule is the easiest to understand by evaluating <n'l'm'|z|nlm>
(2) We have the...
Good afternoon,
Does the selection rules have a condition on \Delta n ? I have not found a website or a book that show transitions between 2S_{1/2} and 2P_{3/2}, that's why I was wondering if \Delta n = 0, with respect to the other selection rules, are allowed transitions.
Thank you for your...
To be specific, I am referring to CO molecules undergoing collisions with H2, resulting in CO transitioning to an excited vibrational state. I can't seem to find any rotational selection rules for collisions, meaning ΔJ could be essentially anything, as long as energy and angular/linear momentum...
Some literatures say that the selection rule in electric dipole approx. for angular momentum ##\Delta j = 0,-1,1## some other say ##\Delta l = -1,1##. I follow the notation used in my references, despite the difference I think since j and l are both angular momenta which fulfill angular momentum...
When we first learn of selection rules for atomic transitions, we learn that electrons have to change between states that differ in angular momentum by at most 1ħ, because photons have 1 unit of spin angular momentum.
However, photons can have arbitrarily high integer quantities of orbital...
Suppose we define the total angular momentum as F = I+J where I is the nuclear spin angular momentum and J is the total electronic angular momentum. mF and mJ are the respective magnetic quantum numbers.
The relevant F selection rules are delta_mF = 0, 1 and -1, delta_F = 0, 1 and -1.
And...
My instructor was talking about allowed transitions for IR spectroscopy and how you can predict them relatively well using PIB wavefunctions. It was stated that you could solve for the probability of a transition moment to determine if a transition is forbidden or not.
<μ>=∫ΨfμΨidτ...
For an atom, the single photon electric dipole selection rules for the magnetic quantum number require that delta_m = -1, 0 or +1.
As I understand, the physical explanation for this set of selection rules is usually related to the conservation of the projection of the angular momentum on the...
Homework Statement
Strong emission lines from calcium were observed at ##422.7nm##, ##610.3nm##, ##612.3nm##, ##616.3nm##, ##1034.9nm##, from transitions between ##4s^2##, ##4s5s## and ##4s4p##. The transition of ##422.7nm## was also observed at absorption. The singlet-triplet splitting of...
Hi,
I'm looking get a deeper conceptual grip on A&M spectroscopy, particularly what actually goes on between atoms/molecules and photons during an emission/absorption event. In general I just want to understand the "why's and how's" of the selection rules for dipole/quadrupole transitions, but...
I have a couple of questions about selection rules for the hydrogen atom.
When we talk about these rules in an undergraduate context we are usually assuming LS coupling where we ignore spin orbit coupling so orbital and spin angular momentum are essentially independent. Is that correct...
Please see attachment. What are the arrow heads supposed to mean? Only emission is allowed and no absorption?
I mean, selection rules allow Δl=±1. But the figure is saying otherwise.
I also read in another book, that the only series observed in absorption is that to the ground state, where...
Hi, I'm a little confused by the selection rules for atomic transitions. In pretty much any standard QM text, they derive the fact that an electron can't transition in an atom unless \Delta\ell=\pm1, i.e. unless the orbital angular momentum changes by one unit. Then the books go on to say that...
If you have a meson in the states
## ^3S_1## and ## ^1S_0 ## this means that ##J^P = 1^+ ## and ## 0^+## doesn't it?
But if you have excited states
## ^1P_1 ## this is ##J^P=1^- ## but isn't ## ^3P_1 ## supposed to be ##J^P = 1^- ##? Does this matter?
##^3P_0##, ##^3P_1## and ##^3P_2## for...
Hi all , I need some help with this problem,
Homework Statement
A hydrogen atom, which is in its ground state |1 0 0 > , is put into a weak time-dependent external electric field, which points into the z direction:
\boldsymbol{E}(t,\boldsymbol{r}) =...
Hi
I am reading about transition in Helium, and I have come across a question. It is clear that triplet-singlet transition are not allowed, i.e. ΔS=0. But in my book (Foot's Atomic Physics) it says that Δl = ±1. This is what I don't understand. The selection rule Δl = ±1 we derived for...
Homework Statement
From past paper:
State the selection rules for (electric) quantum numbers n,l,m,s and j.
Homework Equations
The Attempt at a Solution
My problem is that looking online, there seems to be an m(s) and m(l). Is the question assuming that I state the selectrion...
Hi
I'm trying to figure out how to get the electric dipole selection rules for an atom with many electrons. In all textbooks that I've seen it's shown for Hydrogen, or in the central field approximation (which is, in some sense, equivalent to Hydrogen).
Obviously the central field...
Why is there no allowed transition from the 2s^2 S_{\frac{1}{2}} state to the 2p^2 P_{\frac{3}{2}} state in the attached image? It seems to fulfill the selection rules \Delta l = \pm 1 and \Delta j = 0, \pm 1. This is for electric dipole transitions by the way.
hey,
I was asking myself a few questions about the selection rules for EM dipole radiation which occurs if electrons "jump" into lower bound states according to the selection rules.
now I know that the full explanation about matrix elements of the dipole operator comes from fermi's golden...
I am having trouble showing:
<4 3 0 | p_z^2 | 4 0 0 > = 0 and
<4 2 1 | x p_y | 3 1 0 > = 0
I know the usual selection rules for parity, spherical tensors (Wigner-Eckart for x,y,z) but I can't convert these two to anything I know.
You could also help by telling me how to convert these to...
The transition in the n=2 state of Helium from 3P1 (m=0) to 3S1 (m=0) is forbidden. I know this, because I went to a lecture where a group measured the fine structure constant very precisely using this fact. However, as far as I can see, according to atomic selection rules (available here...
I am reading some online article on Zeeman effect
http://math.ucr.edu/home/baez/spin/node10.html
In the article, the author mentions 4 selection rules, I wonder the corresponding transition is allowed by satisfying one of these selection rules or the corresponding line will be allowed only...
hello
I got al little bit confused about spins flipping in an EPR experiment. As far as I know, the idea of EPR is to measure the absorption of an electromagnetic wave induced by spin flips if the energy is conserved by
\hbar \omega = g_{spin} \mu_B B_0.
But now I heard several times that a...
Homework Statement
For \Deltal = 0 the transition rate can be obtained by evaluating the electric dipole matrix elements
given by
\vec{I} = \int \Psi^{*}_{1,0,0} (e \vec{r}) \Psi_{2,0,0} d\tau
Homework Equations
The Attempt at a Solution
I've got the two wave functions...
I'm quite confuse with some concepts here.
The selection rules are derived from the requirements that quantum numbers must be conserved. It's OK. Then I see they give rules for so-called electric dipole transitions. I just wonder why dipole comes in here. How do you classify these kinds of...
If you have an operator which in spherical tensor language
T^k_q
are
V=T^2_2 + T^2_{-2} + T^2_0
you get a selection rule for j'
abs(j-k)=< j' <= j+k
in my case i start with angular momentum j=1 and k=2 from above so
the possible new states are
1=< j' <= 3...
Hi,
I am confused about the electric dipole selection rules.
Delta l = +/- 1
Delta m_l = 0, +/- 1
but are there rules for Delta j and Delta m_s and Delta n?
Is there a (semi-rigorous) way to conceptually understand selection rules?
Thanks.
Hi, I have a question on selection rules for electric dipole transitions. It has to do with a GRE Physics exam question that's confusing a number of students at grephysics.net ... if any of the quantum guru's here would like to help, please check it out at...