What is Excited: Definition and 171 Discussions

In quantum mechanics, an excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum). Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being raised to an excited state. The temperature of a group of particles is indicative of the level of excitation (with the notable exception of systems that exhibit negative temperature).
The lifetime of a system in an excited state is usually short: spontaneous or induced emission of a quantum of energy (such as a photon or a phonon) usually occurs shortly after the system is promoted to the excited state, returning the system to a state with lower energy (a less excited state or the ground state). This return to a lower energy level is often loosely described as decay and is the inverse of excitation.
Long-lived excited states are often called metastable. Long-lived nuclear isomers and singlet oxygen are two examples of this.

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  1. K

    A Spontaneous emission and coherence

    Assume I prepare a linear superposition ##\frac{1}{\sqrt{2}}(|g>+|e>)## between a ground and excited level for a large number of "atoms" (it can by any multilevel system, not necessarily an atom). We can assume that the lifetime of the excited level is long enough to allow us to create this...
  2. jjson775

    Ratio of Excited Neon Atoms in 5s compared to 3p

  3. Mustafa Bayram

    B The Mystery of Excited Electrons: Are They Moving Away from the Nucleus?

    when an electron is excited to the conduction band is it move further from the nucleus? Are free electrons in the conduction band further from valence electrons? I saw this picture that seems problematic to me. what do you think?
  4. Pipsqueakalchemist

    Engineering Separately excited DC motor problem (Electrical Engineering)

    Hello, so for this question I know how to solve it but I still have a few questions. First when the question means it's rated at 20 HP and 600 V, it's referring to the source voltage and Pin correct? Also in order to solve this question, the rotation loss Prot was neglected. This was because at...
  5. lua

    Upper bound for first excited state - variational principle

    I'm solving problem number 5 from https://ocw.mit.edu/courses/8-05-quantum-physics-ii-fall-2013/resources/mit8_05f13_ps2/. (a) Here I got: $$ \beta = \frac{\hbar^{\frac{1}{3}}}{(\alpha m)^\frac{1}{6}} $$ and: $$ E = \left ( \frac{\alpha \hbar^4}{m^2} \right )^\frac{1}{3}e $$ (b) Using Scilab I...
  6. P

    I Electron transitions within the same excited state?

    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...
  7. D

    A "Cross-section" and "half-life" of excited states

    Hello, I work with a spectrometer that does ionizations through laser 2+1 photons resonant ionization (a high power narrow bandwidth laser is tuned to a precise wavelenght so that it allows reaching an excited energy level of a particular element with the sum of two photons absorbed...
  8. N

    B Do emission nebula glow because of ionised or excited electrons?

    I'm trying to figure out why emission nebulae glow. I read various sites such as a NASA website explaining why they shine; 'The massive stars embedded within the nebula give off enormous amounts of ultraviolet radiation, ionizing the gas and causing it to shine.' The Britanica article on...
  9. Jozefina Gramatikova

    Calculating Gamma, L, R1,2 for Excited Ions

    For part b) Gamma is the cavity loss coefficient, L is the length of the rod, R1,2 are the reflectivities. I am not sure how to find the number of ions in the excited state since I don't know the number of ions in the ground state.
  10. H

    The energy of the first excited state of the system

    Five electrons are in a two-dimensional square potential energy well with sides of length L. The potential energy is infinite at the sides and zero inside. The single-particle energies are given by (h^2/8mL^2) (nx^2+ ny^2) where nx and ny are integers. The energy of the first excited state of...
  11. M

    I Excited system in a harmonic potential

    Hello! Assume we have a simple harmonic oscillator potential, in 3D (say created by some electric fields, such as a Paul trap) and inside it we have a 2 level system in the excited state (say an ion in which we care only about 2 levels, for example the lowest 2). The translational energy of the...
  12. F

    Engineering Find the brake torque in separately excited machine

    Here's my attempt for part 1a: What I am not sure about is the direction, is it in the opposite direction (= - 458.37 N.m ) or it's positive? Thanks,
  13. F

    Engineering Continuous and discontinuous modes of series excited DC motors

    Here's my attempt: clc; clear all; Ra=1.8; La=150*10^(-3); Ls=150*10^(-3); Rs=1.8; Rt=Rs+Ra; ws=100*pi; c=1.25; vrms=240; vm=240*sqrt(2); f=50; T=1:0.5:50; for a=0:pi/9:pi/3 vt=(2*vm*cos(a))/pi wc=((ws*(Ls+La)/tan(a))-Rs-Ra)/c; x=[wc; a+pi]; Tc=c*(2*vm*cos(a)/(pi*(c*wc+Ra+Rs)))^2; for...
  14. B

    Self Excited AC Single Phase Generator

    Hi I'm doing a uni project and need help with a Self Excited AC Single Phase Generator. I'm using an AC Single Phase Induction Motor to act as the generator. Its turned by a DC Motor The AC motor is 1350 RPM and the DC motor is 2500 RPM Its not producing any electricity (just a few volts) for...
  15. P

    Case when the potential energy of the 1st excited state is zero

    I know how to solve this problem when the energy at ground state is zero but I don't know how to deal with 1st excited state energy as zero. According to me since the potential energy is zero therefore the kinetic energy must be 13.6eV according to conservation of energy. I also know that the...
  16. B

    Principle quantum number n of the excited state

    Here is a question I have been given I have started by setting up the formula and rearranging for n_2 Only problem is that I do not know the quantum number for ground state? What value do I sub in for n_1? Any help would be appreciated! Thanks
  17. K

    I Static and dynamic excited states

    Hello! I am reading about excited levels in nuclei (I am mainly following Wong's nuclear physics book) and I am a bit confused about the nature of the excited states. In the one particle picture (mainly shell model) the excitation appears as static i.e. one nucleon moves from a certain orbital...
  18. K

    I Low-lying excited states in nuclei

    Hello! How are the parity and spin of excited states of nuclei measured experimentally. I imagine that the energy can be easily measured by exciting the nucleus (by colliding it with a nucleon or electron for example) and then measuring the emitted photons. But how can one infer the spin and...
  19. jisbon

    Electron excited from the ground state to a quantum state

    Hi there, popping by here to check my answer because another online platform has already answered it but my answer appears to be wrong. I can't seem to understand why though :/ Since I can find the energy at a state to be ##E_{n}=\dfrac {-13.6z^{2}}{n^{2}}eV## At ground state where n=1...
  20. H

    A Overlap of nth QHO excited state and momentum-shifted QHO ground state

    ##\newcommand{\ket}[1]{|#1\rangle}## ##\newcommand{\bra}[1]{\langle#1|}## I have a momentum-shifting operator ##e^{i\Delta p x/\hbar}## acting on the ground state ##\ket{0}## of the QHO, and I want to compute the overlap of this state with the n##^{th}## excited QHO state ##\ket{n}##. Given...
  21. GuillemVS

    I How to choose the way an excited electron loses energy?

    When electrons get excited they are unstable, therefore they want to go back to ground state. One way they do so is by creating photons (e.g. mirrors), but I've also read that they can create electricity (another electron?). Photoelectric is how it's called, right? If so, how can we choose...
  22. GuillemVS

    I Excited electrons' behaviour, how do they work?

    Mainly I want to know the following thing: electrons when excited they tend to want to go back to ground state, right? One way is by photons, but how does that work? Accelerating charges creates EM waves, but in this case there was no acceleration, right? Or is the term accelerating only a way...
  23. Greg Bernhardt

    Excited to go to Brian Cox's "ADVENTURES IN SPACE & TIME" tonight

    Tonight I'm taking my wife and parents to Brian Cox's World Tour "ADVENTURES IN SPACE & TIME" with sidekick Robin Ince. All his European stops sold out and so far all of his US stops have been close to selling out. I've been impressed because he's not quite the household name Neil deGrasse Tyson...
  24. B

    Binding energy and excited nucleus question

    this is from a website on why gamma rays are released what i don't understand is, why is the mass defect lead to a gamma radiation to be formed. If the nucleus is excited and dexcites the change in energy levels would cause a photon to be released. yet here it says the mass defect is the source...
  25. O

    Statistics physics problem -- atom is in the ground state or excited state?

    I am learning for my exam in particle physics. One topic is statistical physics. There I ran into this question: Consider an atom at the surface of the Sun, where the temperature is 6000 K. The atom can exist in only 2 states. The ground state is an s state and the excited state at 1.25 eV is a...
  26. S

    How can I make the most out of my experience on this physics forum?

    Hello everyone! I'm currently a physics student in my sophomore year of undergrad. I just stumbled upon this forum and am curious about the site - very excited to explore and enjoy the ride. If anyone could give me any tips about using these forums and this site in general, it would be much...
  27. R

    I Question about excited Helium states

    Most of the books I've seen they say that the first excited state of Helium (with two electrons, one in orbital 1s and other in 2s) can have the two electrons with parallel spin (orthohelium) or anti-parallel spin (parahelium). If ##\operatorname{X_{↑}}{\left (n \right )}## represent the state...
  28. C

    Ground state and 1st excited state energy of 3 Fermions

    Homework Statement So in my problem, there's a given of 3 non interacting fermions in a harmonic well potential. I already got the wavefunction but i have problems in obtaining the ground state energy and its 1st excited state energy for 3 fermions (assuming they are non interacting and...
  29. mesa

    Looking for excited state gamma emission data on everything?

    Hey guys, I am looking for a database on gamma emission from the first few excited states of known isotopes for a piece of software we are putting together. Any format is fine. Thanks!
  30. N

    Is this really an excited state?

    The figure below is from a textbook. It is explaining what excited states are using carbon as an example. I don't necessarily agree that the the state labeled as "example excited state 1" is really an excited state. Since the electrons in the 2p orbitals are unpaired, and in the absence of a...
  31. J

    A Holographic Relations for OPE Blocks in Excited States

    Holographic Relations for OPE Blocks in Excited States https://arxiv.org/pdf/1809.09107.pdf Jesse C. Cresswell†1 , Ian T. Jardine†2 , and Amanda W. Peet†§3 †Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada §Department of Mathematics, University of Toronto, Toronto, ON...
  32. P

    A Young's double slit experiment with excited atoms

    i would like to find the detailed calculation in the case of a two slits experiment with an excited atom. i only found the formulas when it decays near the slits. have you links? thanks
  33. QuarkDecay

    A Doubly excited Atom of Helium

    The Atom of Helium is doubly excited in 2p2 1D Can someone explain to me how these energy symbols work? I have a problem with what the 1D means specifically. I know 2p2 means two electrons in the 2p state. The 1 in 1D could be referring to electron being in a singleton, but I don't understand...
  34. HastiM

    Electrons excited by absorption of a photon in Mg

    Homework Statement The total spin of an Mg atom is zero and remains zero after absorption or emission of a photon. To which states can one of the electrons in the outer shell get by absorption of a single photon: 4s, 5s, 3p, 4p, 3d, 4d?2. The attempt at a solution I am not sure which of the...
  35. C

    Uncertainty Principle and the lifetime of an excited state

    Homework Statement [/B] Estimate the lifetime of the excited state of an atom whose natural emission line width is 3.00 × 10−4 eV. Homework Equations $$ \Delta E \Delta t = \frac{1}{2} \times \frac{h}{2\pi} $$ $$ \Delta E \Delta t = \frac{h}{2\pi} $$The Attempt at a Solution I think all I...
  36. A

    Term symbol of a molecule in an excited state

    Homework Statement Considering the molecule of ##C_2^+## in an excited state with valence configuration ##2\sigma_g^2## ##2\sigma_u^2## ##1\pi_u^2## ##3\sigma_g^1##. Finding all the possible term symbol. Homework Equations Term symbol ##^{2S+1}\Lambda## ##L=0 \rightarrow \Sigma## ##L=1...
  37. ohwilleke

    I Excited hadrons v. fundamental particles

    Mesons and baryons have both a ground state and excited states involving the same valence quarks but a higher mass (which can in principle be calculated from QCD). Fundamental fermions and bosons, however, do not appear to display this behavior. They have a ground state, and while there are...
  38. T

    Lagging or leading synchronous generator

    Hi, It has been a long time since I studied synchronous machines and I am trying to understand the mechanism of how the armature excitation can result in the generator being lagging or leading. So please correct me if I say something like it's axiomatic but its really erroneous. Now, according...
  39. sumit_1

    The lifetime of the excited states of a hydrogen atom?

    How can we differentiate among the lifetimes of the excited states of the hydrogen atom? The states are: 2p, 2s, 3s, 3p
  40. T

    B Decay of Excited Atoms: Probability & Nonlinearity

    I learned that the probability of radioactive decay for an atom is always the same. However, is the decay of and excited atom or electron non linear(decay probability varies with time)?
  41. J

    I First excited state of Helium. Triplets and Singlet

    My question is the following one: If i have the first excited state of helium, the possibilities for the two electrons are : 1s+,2s+ , 1s+2s-, 1s-,2s- and 1s-,2s+ , where + and - denotes spin up and down. If I use the slater's determinant to generate antisymmetric states, I get : $$|u1> =...
  42. L

    Compute the energy of the emitted alpha for Na20 decaying to an excited state

    I think I got this right, I just want a second opinion to know if my concepts are correct 1. Homework Statement 20Na decays to an excited state of 20Ne through the emission of positrons of maximum kinetic energy 5.55 MeV. The excited state decays by ##\alpha## emission to the ground state of...
  43. C

    I How can an atom change from ground to excited state?

    I am currently studying a Foundation Program, which includes chemistry. -I can easily understand the distinguishable characteristics between ground and excited state via writing the electron configuration. -But how can an tom changes from ground to excited state ? And can an atom changes from...
  44. J

    Engineering How Does Armature Voltage Affect the Speed of a Separately Excited DC Motor?

    Homework Statement A 180V separately excited DC motor has an armature resistance of 1.2ohm. When the note runs at 1200rpm,t he armature current is 10A. 1) Assuming that motor torque is constant at all speeds,d determine the mechanical torque and power developed in the motor. 2)Find the speed of...
  45. P

    High n transitions (eg 109-108) are observed in excited He...

    Homework Statement Transitions between n=109 to n=108 have been observed in highly excited helium atoms and in this case the Bohr model is a valid approximation. Why is this? Homework Equations N/A The Attempt at a Solution I'm having some problems with this question and it probably comes...
  46. Kara386

    Energy shift in excited state sodium

    Homework Statement The spin-orbit interaction in sodium results in fine structure with energy shifts given by: ##\Delta E_j = \frac{C}{2}[j(j+1)-l(l+1)-s(s+1)]## If ##l##, ##s## and ##j## describe the single outer electron in sodium. Show that if this electron is excited to a state where l>0...
  47. R

    What are thermally excited holes and how do they aid in decomposition?

    I am looking at a paper that takes about thermally excited holes in relation to photocatalytic destruction, another paper with the same substance (TiO2) talks about decomposition of polycarbonates with the same method (thermally excited holes). I'm a little rusty on this topic. Please could...
  48. P

    Predicting spin and parity of excited states from shell mode

    Homework Statement Consider the following example from a previous exam. We are to predict the spin and parity for F(A=17,Z=9), Florine, in the ground state and the first two excited states using the shell model. Ground state: Neutrons: (1s 1/2)^2 (1p 3/2)^4 (1p 1/2)^2 Protons: (1s 1/2)^2...
  49. G

    Automotive Load Spectrum and excited frequency

    Hi all! I have the following spectrum for a signal force: and this is a zoom in the range of interest: Can I state that this force is capable of exciting the natural frequency of the structure ( in the range 5-30Hz) or the force amplitude in this range is too low compared to the peak...
  50. nmsurobert

    Exploring Excited Evanescent Waves and the Minimum Incident Angle

    Homework Statement A glass prism is used to launch an evanescent wave along a glass-air interface. What is the minimum incident angle to excite the evanescent wave? Homework EquationsThe Attempt at a Solution I don't understand what the question is asking for. I have read and reread the...
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