Questions tagged [absorption]

A transition by which the energy of at least one photon is completely transferred to a material.

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Understanding the virtual states referenced in multiphoton absorption studies

The Heisenberg energy-time uncertainty tells us that we can have so-called virtual states between eigenstates as long as the lifetime of these states is at most: $\tau = (\frac{h}{4 \pi E_v})$ Where ...
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Paint: “Darker When Dry”?

A great question I enjoy bringing up is why are things, in general, "darker when wet". This applies to porous and granular materials like wetted stone, paper, sand etc. It also comes up in painting ...
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Relationship between oscillator strength and cross-section

In the context of absorption of photons by atoms, I have come across two seemingly very related quantities, cross section and oscillator strength. In the book Physics of the Interstellar and ...
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236 views

How much heat do colors absorb?

A common grade school experiment is to compare how hot different materials get in direct sunlight. See examples here, here and here for example. The premise is generally two identical objects of ...
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244 views

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 ...
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Complex part of second-order susceptibility in nonlinear optics

In optics, the absorption of photons by a material can be described by considering the material's susceptibility. For linear absorption (involving a single photon), we think about the imaginary part ...
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Two Photon Absorption dependence on Semiconductor Band Gap

It's well known that Two Photon Absorption coefficient is scaling with $E_g^{-3}$. Does anyone know what is the physical reason for this scaling? What is the physical theory behind this mathematics?
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A Problem about Line Broadening and Absorption coefficient

I am reading my textbook, Lasers by Anthony E. Siegman, and I just could not understand a point he made. In the chapter section about inhomogeneous broadening, he used a figure to show the transition ...
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Can water be made more violet?

Water is intrinsically blue because of molecular vibrations. The topic is covered here: Only sea water appears blue in color, why this is not happening in river water? And here, which I post ...
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Feynman’s Treatment of an Opaque Wall

First time poster. I’ve been reading Feynman’s Lectures on Physics, and I’ve just finished reading his treatment on diffraction. Feynman described a method of thinking about an opaque wall that was ...
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In diffraction When wavelength is less than slit width then does the scattered light gets absorbed & emitted from the wall or just rebound?

I know that when the slit width is less than that of wavelength then the slit will act as a point source and scatter the light in all directions. But my question is that during the scattering of ...
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Rate of direct (non-thermal) photon-induced evaporation of water?

I have read a long time ago of early experiments in the evaporation rate of surface water, and a discovery that in addition to the Sun's impact on the temperature of the water, it was believed that ...
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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 ...
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Light Inside a Spherical Droplet

Suppose that a monochromatic light beam of wavelength $\lambda$ bounces around inside a perfectly spherical droplet of glycerol (radius $r$, refractive index $n$, density $\rho$, molar mass $M$) ...
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Why does it take time for absorption to set in?

I read this sentence in Optics Principles and Applications by Sharma regarding light dispersion: But since it takes some time for the absorption to set in, the trailing edge of the pulse is ...
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Book on spectroscopy (line dependency on parameters)

I am trying to find a book (undergraduate level) on Spectroscopy. I am interested in how molecular absorption lines depend on parameters like temperature and pressure (for example with gases). Can ...
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Connection: Work on dipole <-> optical absorption

If I consider a two-level system with a ground and an excited state, I can compute the instantaneous rate at which work is being done on the dipole $\mu(t)$ by an electric field $E(t)$: $\dot{W} = E(...
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The resolution limit for lithography in practice?

For a given wavelength of light $\lambda$, and a given numerical aperture (NA), I always see the statement in papers/etc. that we can perform lithographic patterning at the Rayleigh limit given by $\...
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Does absorption in the cladding material change the real value of the propagation constant of a waveguide?

Imagine two scenarios: two cladding materials with the same real refractive index, but one has absorption while the other does not. Now, these materials act as the top cladding of a waveguide (for ...
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1answer
76 views

Recoil velocity of atom after photon absorption

I'm trying to calculate the recoil velocity of a stationary atom after absorbing a photon, in terms of $E$ and $m$. I've tried manipulating relativistic equations, keeping in mind conservation of ...
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Transmission Spectrum of Rock

Maybe a very specific question, but what wavelengths are sand grains transparent to? Also, how can one image underground minerals through rock? Is there a certain Infrared band that sandstone (...
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170 views

Interpretation of the photon scattering rate?

The photon scattering rate $\Gamma$ describes the rate at which photons scatter off an atom$^1$. In a two-level system, the ansatz for the photon scattering rate often is given by \begin{equation} \...
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List of complex refractive indices for various frequencies and various materials

I want a list of refractive index values for various materials (or even a single material) for various frequencies / wavelengths (I need this specifically for the micro wave - radio wave regions of ...
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112 views

Plasma Frequency of Indium Tin Oxide

What does determine the plasma frequency? The formula is: $$\omega_p² = \frac{4 \pi N e²}{m}$$ and for frequencies above the plasma frequency the material is transparent. So for indium tin oxide (...
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How would gray dust work, on a microscopic level?

I came across an article on something called gray dust, a hypothetical substance explored theoretically during the early 2000s. It attempted to explain cosmological supernova observations by ...
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70 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 ...
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What are some mechanisms that can lead to unexpected/anomalous spectral lines

I am studying fluorescent spectroscopy (laser-induced fluorescence spectroscopy specifically). In a particular atomic spectrum, there are some unexpected lines not associated with any known ...
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Partial absortion of a photon

In atoms, there are electronic energy levels, when there is a match between those and a light photon energy, an electronic transition ocurs. Example and question Suppose an atom has a levels $0$, $1$...
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58 views

The Attenuation of Light

I have this question: Show that the attenuation of light as it travels through the interstellar medium follows an exponential law My initial thoughts were to demonstrate the absorption of ...
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Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
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96 views

Dielectric constants from refractive index and absorption spectra

I would like to calculate the dispersion relation (dielectric constants $\varepsilon'$ and $\varepsilon''$) from two spectra: refractive index $n$ and absorption (in %). I tried to use the relation $$\...
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Temperature profile of the atmosphere due to absorption by a gas

I want to observe the temperature profile of the atmosphere due to absorption by a gas such as water vapor. I know that optical thickness changes as the density of the gas changes with altitude in the ...
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Are changes in light aborption induced by changes in medium concentration multiplicative with light intensity?

I'm working in the area of near-infrared spectroscopy where we shine light through tissue and measure the attenuation at a detector nearby. The detector is actually placed on the same surface as the ...
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How does the reflectivity of a light-source change when it's switched on/off?

Q: How does the reflectivity of a light-source change when it is switched on/off? Consider a light-source like an red LED with some white light shining on it. When the LED's switched off, it's going ...
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References for photo-absorption on a nucleus

I have spent lots of time looking for at least one good reference for nuclear photo-absorption, but it seems like most of the authors I ran into prefer not to make fundamental references. Does anybody ...
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What is 'stimulated inhibition'?

I have heard that the equivalent to 'stimulated emission' (which occurs with bosons) for fermions is something called 'stimulated inhibition'. Please can someone explain what this processes is, and ...
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56 views

Photon scattering and absorption in solution

I have a situation where I have an organic dye in aqueous solution, through which I have sent a (green) laser beam and measured the intensity. Compared to pure water, this solution showed much greater ...
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232 views

Emissivity of transparent window

I've been reading this article where the IR radiance of an IR-window ($MgF_2$, 1.75mm thick, passband 3-5$\mu m$) is calculated. At some point during the calculation they mention in a footnote: The ...
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2answers
127 views

Mie theory: Interpretation in terms of intensity

I'm trying to understand Mie theory. For this I'm reading the book "Absorption and Scattering of Light by Small Particles" by Bohren and Huffman. The derivation of the formulas is fine, but I'm stuck ...
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Do you know if you have zerovalent iron nanoparticles in liquid how to measure minimal magnetic force required for separation of these nanoparticles?

I think of measuring mag susceptibility from VSM data (magnetization divided by the applied field) but I am not sure if this would be enough. Maybe if I employ SQUID measurements, but in that case I ...
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Sound range and depth it travells whe it hits sound

I know most people hear from 20hz to 20000hz and about the absorption spectrum of water absorption spectrum of water link but how deep does sound travel when it hits the skin and which range of ...
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58 views

Can a photon that matches the energy gap pass through a molecule?

I've heard that atoms and molecules are made up of mostly empty space. I've heard that electrons exist as a probability cloud around and/or between atoms and molecules. My question is, is there a ...
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Absorption Spectrum

I just learnt what absorption and emission spectrum are. And our teacher introduced us to what Quantum Dots are. And showed us their absorption and emission spectra. And they look something like this ...
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How is the probability of intersystem crossing influenced by small differences in energy levels?

Say I have some dye molecule in some low level triplet state, e.g. $T_1$, and it's decaying slowly to the ground state via phosphorescence. However, there are also events where the dye in the $T_1$ ...
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Why do “virtual states” in Raman spectroscopy have absorbance profiles distinct from either the ground or excited states of an absorbing material?

Do virtual states in Raman spectroscopy have distinct and observable dipoles that can interact with and/or induce dipoles in other molecules (over extremely short femtosecond timescales)? This notion ...
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67 views

Absorption from a classical to quantum

Today, I learned that using rubidium atoms at very low temperature in a Magneto-optical trap, one can experimentally show that the Lorentz classical derivation of absorption using dipole is valid. The ...
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What happens in the case that the incident light on an atom has photons with insufficient energies to excite an electron?

When an atom of an element is irradiated with a monochromatic light, what will happen in the case that the frequency of the light does not match the frequency needed for any of the several possible ...
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Problem regarding the absorption spectrum of the sun

Some of the wavelengths of light that are emitted from the sun will be absorbed by atoms in the outer layer of the sun and also the atmosphere of the sun, and we see this as absorption lines in the ...
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Determine molar extinction coefficient from data set

How can you determine molar extinction coefficient from the graph of Transmittance vs Wavelength, where the solution concentration and thickness of cuvette are known and constant by using Beer-Lambert ...
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Ultra-violet optical transitions for $\rm ZnO$?

Is there any paper discussing the d(GAMMA3)-GAMMA1 optical transitions at around 7 eV for $\rm ZnO$ (W)? Will the negative effective mass/saddle point makes it a 2D (M1) transitions?