What is Absorption: Definition and 531 Discussions

Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum.
Absorption spectroscopy is employed as an analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. Infrared and ultraviolet–visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in studies of molecular and atomic physics, astronomical spectroscopy and remote sensing.
There are a wide range of experimental approaches for measuring absorption spectra. The most common arrangement is to direct a generated beam of radiation at a sample and detect the intensity of the radiation that passes through it. The transmitted energy can be used to calculate the absorption. The source, sample arrangement and detection technique vary significantly depending on the frequency range and the purpose of the experiment.
Following are the major types of absorption spectroscopy:

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1. Optimal thin absorber of electromagnetic energy

Hi, I am a material engineer and have a question about a formula derivation relative to microwave absorption. I really cannot figure it out after days of trying. This should be simple for a specialist. In this attached paper, how could one derive Eq(10) based on Eq (8) and (9)? Is k_2 in Eq...
2. Question about Absorption Laws in Boolean Algebra

According to my notes, the absorption law states that p ∨ (p ∧ q) = p, p ∧ (p ∨ q) = p I have found a video where they were discussing a partial absorption such as ¬q ∧ (¬p∨q) = ¬q ∧ ¬p This is not in my notes, but is this correct? specifically, is the terminology used to decribe this property...

22. A Absorption of an Exciton and Exciton propagation

I read articles talk about the absorption of the exciton in a solvent, such as TIPS Pentracene in toluene. My question is does the absorption spectrum keep the same for aggregate TIPS Pentracene , in case if I want to know for a layer of TIPS Pentracene?! My second question is: let's say I know...
23. Specific Absorption Rate(SAR) - caused from radio frequency from mobile phones

Why SAR value at body is allways higher than at head?
24. Engineering Light absorption in a semiconductor

The doped a-Si: H layers in a HIT solar cell do not contribute to the photocurrent. The light they absorb (according to their absorption curve below) is lost. For a doped a-Si: H layer at the front side of the cell that is 25nm thick, what percentage of light at 400nm will be lost due to...
25. B Absorption of beta particles by lead

Hello everyone, We conducted an experiment with a strontium-90 source and some different thicknesses of lead. With 2.1mm of lead the count rate (corrected for the background) was 0.69 counts per second, 3.0mm 19.7cps 6.8mm 15.4cps 13.8mm 10.0 cps This would...
26. I Photon absorption for an atomic electron

Quick question: let's say we have an atomic electron in the ground state which requires, say, one "unit" of energy* to jump up to the next orbital energy state. If a photon arrives with a bit more or less than this, say 1.00003 or 0.99997 units of energy, is there some finite, non-zero...
27. I Absorption lines and emission lines in stellar spectra

Why do we see more absorption lines in stellar spectra than emission lines?
28. I Why Do We Have The Effect Of Spontaneous Emission And Absorption

Hi All In another thread I answered was a question related to this and noticed another as well, so I thought I would give the full answer in its own thread rather than write it out twice. The other question has been deleted but here is the full detail anyway. First see...
29. Deconvolve absorption from this spectrometer signal

Hello all, I have a monochromatic laser peaking at 808 nm and some non-scattering sample. I want to measure the absorption with a spectrometer. I can use the Beer-Lambert law to do this, but since it is a monochromatic laser I have some doubts. I could do a weighted-average, taking into...
30. Understanding Radio Waves & Oxygen Absorption at 60GHz

Homework Statement: I am having difficulty understanding what exactly is happening when radio transmissions are being absorbed by oxygen at 60GHz at the atomic level. Homework Equations: Refraction/reflection, oxygen absorptions/attenuation, frequency I have tried to find the answers online...
31. A Trying to meaningfully deconvolute IR absorption spectra

Hi I'm preparing some BCNO phosphor samples. Their basic structure is hexagonal Boron Nitride (h-BN) but it's doped with carbon and oxygen. The simplest BCNO phosphors are usually made from urea and boric acid alone, this already produces a BN structure with C and O impurities. I'm trying to...
32. Exploring Black & White Materials: Absorption vs. Reflection

True black materials theoretically absorbs all wavelengths of visible light. True white materials reflect all wavelengths of light. If a material which was black at room temperature was heated up to incandescence so that it was emitting all visible wavelengths (white light), and then light was...
33. How to Measure Impact Force / Energy Absorption

Hi, I am a bit out of my league here, but had a question. I have 5 pieces of .25" thick foam/padding of different densities, and I wanted to measure which one absorbs the most energy (weakens the impact) when struck by a fist/punch or even a ball, how would I do that? I ran across a...
34. Infrared energy absorption of H20 molecules as a percentage of energy

I eventually managed to find that a CO2 molecule can absorb about 8% of infrared energy passing through it that's radiated from Earth but its actually been incredibly hard to find a comparable figure for H2O molecules. Has anyone got a percentage figure for H2O in the form of atmospheric water...
35. Absorption Spectrum Practice problem

Summary: The experimentally measured absorption spectrum of 1,3-pentadiene molecule exhibits a peak absorption (light absorption) around 224 nm corresponding to an electronic transition. Estimate the length of the molecule. I thought of using lambert law A = c*l*e but we have none. how do I...
36. MIT Material 10x Blacker Than Any Other: 99.995% Light Absorption

Summary: MIT researchers have created a material that is 10x blacker than any other material ever recorded. The foil captures at least 99.995% of incoming light. Does this mean that there is practically no EM re-radiated?
37. I What happens to an electron's frequency during absorption of a photon?

The point that I want to know is how two frequencys react with each other and does electron's frequency wait to reach to higher frequency on that fraction of second when they(photo's frequency and electron's frequency)collapse to each other than go to higher energy level or what?
38. I Photon Absorption & Electrons: Mass, Energy & Releasing Photons

I'm not that familiar with the current theoretical standing on how electrons "absorb" photons, as in the sense that electrons in an atom absorb photons and move from lower to higher energy states. But during the absorption of a photon the electron, if you set units of c=1, gains energy and...
39. Solar cell absorption efficiency in COMSOL Multiphysics

Hi. I am studying the effect of plasmonic nanoparticles on solar cells. Is there a way to calculate absorption efficiency in different layers of tandem solar cells in COMSOL Multiphysics.
40. Atmospheric CO2 absorption - actual quantification?

I have read oodles of hand wavy qualitative text about 'the greenhouse effect' and it is clearly dominated by the absorption characteristics of H2O vapour. What I struggle to understand is the part of CO2 in radiative absorption, in relative quantified terms. CO2 has absorption peaks at 2.7um...
41. Usage of absorption and magnitude mode spectra in nuclear magnetic resonance

In nuclear magnetic resonance, when should one process spectra in absorption mode and when - in magnitude mode? What is benefit of using the first one and the second one? For example, I need to integrate spectrum. In this case, what should I use - absorption or magnitude mode?
42. Acoustic resonance - Absorption vs Transmissibility

Hi everyone. Firstly, I'm not a physicist, so relatively "intuitive" explanations would be greatly appreciated :) I'm confused by the following: Let's say we have a partition / wall, which resonates at a specific natural frequency. If the resonance is relatively high Q (low damping), then...
43. B Absorption of electromagnetic radiation

Hi, I wonder why with electromagnetic radiation, there's some radiation that penetrates with Earth atmosphere such as visible light, while other can't like gamma radiation. What does the penetration of any em radiation on any object depends on
44. I Absorption of Radiation: Calculating Sphere Area

Hello: Do anyone remember a law to calculate an area of a sphere ,some thing like the specific surface area but relative to absorption of radiation ?
45. Water vapor absorption in THz range

Hi everyone! Terahertz time-domain spectroscopy (THz-TDS) is a spectroscopic technique that is using the radiation in the THz range. https://en.wikipedia.org/wiki/Terahertz_time-domain_spectroscopy A THz-TDS setup consists of an emitter and detector. The emitter creates a short broadband...
46. Absorption rate of CO2 in water

So here's an interesting topic and I would appreciate some input from the assembled brains of PF to the question. Unfortunately I can't reveal the background to this but I want to know something about the rate that small bubbles of CO2 are likely to be dissolved in water under moderate pressure...
47. I Confusion about absorption spectra - cool gases absorb?

So I was taught in school that heated low density gases produce spectral lines and cool low density gases absorb their spectral lines. I mentioned this to my husband and he asked me what the definition of hot and cool were and I had no idea. The more I thought about it, the more confused I...
48. On Rayleigh Scattering and UV Light Absorption

I've read that UV light cannot "penetrate" the atmosphere as easily during winter. But what does this exactly mean? My hypothesis is that due to rayleigh scattering, since light with smaller wave lengths scatter more, the UV light doesn't end up reaching the surface of the Earth (i.e. gets...
49. I Photoelectric effect questions: photon absorption and electron ejection....

Is a photon fully absorbed by a electron in metal? Ejected electron is a free electron or bonded one? Is it possible to have a zero work function? If not why? I want to study about this detaily ,can you prefer some reference papers?
50. Confused about the number of absorption lines

Homework Statement If an atom in energy level 1, how many absorption spectral lines can an atom exhibit due to transition between 3 levels? How about 4 and 5 levels? And also in emission? Homework Equations Concept The Attempt at a Solution I am confused one book says it can absorb a photon...