# All Questions

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### Times associated with Absorption and Emission Processes

I am currently reading the book "Advances in Atomic Physics: An Overview" by Cohen-Tannoudji and Guéry-Odelin. In pages 29-31 the authors discuss a two-level atom subject to a broadband radiation ...
118 views

### Radiation pressure and conservation of energy

TL;DR: How can radiation pressure conserve energy, if we consider the case where the atom absorbs all the Energy of the incident photon via its newly excited electron, and stills gains additional ...
43 views

### Raman effect and IR absorption

Let's consider a molecule with N atoms, on which is shot a polychromatic IR beam. From the quantum selection rules, we know that in a single event of absorption only one of the 3N-6 oscillators can be ...
44 views

### What is the difference between upconversion and two photon absorption?

I have read this: https://en.wikipedia.org/wiki/Photon_upconversion And it says that upconversion is a process where subsequential absorption of two or more photons leads to emission of light with ...
98 views

### What happens if we re-excite an excited electron to a higher energy level?

What happens if we re-excite an excited electron to a higher energy level? e.g. we excite hydrogen's electron from n=1 to n=3, then before it gets to return to the ground state, we hit it with ...
113 views

### What is the meaning of a Fourier Transform in an electric field $E(\omega,t)$?

There is this electric field in one dimension: $$E(\omega,t) = E_0 \cos(\omega t)$$ It is reaching the surface of a semiconductor. The number of photons reaching the surface per unit of area is ...
49 views

### given an AC field, how many photons are there?

Say you are applying a time varying potential across double quantum dots in the form of $V_{ac}$cos($2\pi f t$). We know that each photon has an energy $E_{photon}= hf$. Is it correct to say that ...
68 views

### Does photon absorption annihilate the associated EM wave instantly?

My Understanding A single photon has an associated electromagnetic wave. The wave is spread out in space, but the photon is considered a point particle. If the photon is absorbed, the entire wave ...
130 views

### Absorbtion of photon

Electrons in an atom absorbs an incoming Photon to gain energy and jump to a higher energy level (shell or different orbital) considering the fact that the photon doesn't have enough energy to make ...
120 views

### Is there a connection between the frequency of a photon and the oscillation frequency of the atom which absorbs it?

If a photon has energy $E$, we know it has angular frequency $\frac{E}{\hbar}$. If an atom has an energy gap $E$ between its ground and first excited state, we know that if the atom is in a ...
505 views

### How precise must the energies match for absorption of photons?

According to Quantum Mechanics, in order for an atom to absorb a photon the energy of the photon must be precisely that of a "jump" between energy states of the atom. How precise must it be? If I ...