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. C

    Question about probability with absorption

    say we have integers 0-10. We start with N and the probability that N grows by 1 is .69. The probability that N decreases by 1 is .31. Thus obtaining N+1 after one time step is .69 and similar obtaining N-1 is .31. Once N reaches 0 or 10 it is absorbed and can't move from there. My question is...
  2. R

    Discrete math, proving the absorption law

    Homework Statement Prove the second absorption law from Table 1 by showing that if A and B are sets, then A ∩ (A ∪ B) = A. Homework Equations Absorption laws A ∪ (A ∩ B) = A A ∩ (A ∪ B) = A The Attempt at a Solution i will show A ∩ (A ∪ B) is a subset of A x is any element in A...
  3. L

    Molar absorption coefficient of Catechol

    Hi everyone Homework Statement I'm looking for the molar absorption coefficient of Catechol but I can't find it anywhere. Can anyone help me out? I searched the internet as well as some books we have in our library, but I wasn't able to find it. Thanks for you help.
  4. J

    Could dark matter have gamma-ray absorption lines?

    Are there sky surveys that perform gamma-ray absorption spectroscopy? I was wondering if dark matter might absorb gamma radiation. I have done a simple Bohr-atom type calculation assuming a dark matter model of a bound state of a North and South magnetic monopole and found a Rydberg energy...
  5. J

    Calorie to Heat Conversion: Cheese Food Experiment

    The nutrition label on a package of processed cheese food indicates that a 20.0 g serving has 175 Calories. To test this you put a small piece of cheese under a can with 100.0 mL of water and burn the cheese. You find that 1.0 grams of cheese was burned to heat the water. Assume that all of the...
  6. L

    Helium Absorption | Grand Partition Function & <N>

    Homework Statement The atomic site that is in thermal and diffusive equilibrium with a gas of Helium atoms that is on the surface of a metal can either absorb an atom of Helium or it can be vacant. (a) What is the Grand Partition function of the system? (b) Derive the average thermal...
  7. F

    Relation between spontaneous emission, absorption and re-emission

    Hello Forum, when a wavefield is incident of an atom and the photon have the right energy (equal to the band gap energy), the photon is absorbed and disappear... But isn't the photon re-emitted later on and allowed to propagate through the material or does all its energy get lost into heat...
  8. G

    How could I find the rate of heat absorption?

    Homework Statement At what rate is a refrigerator absorbing heat if 2·15 kg of water at 21·5 °C is just frozen in 2·00 h? Homework Equations Q = mL Q = mcΔT The Attempt at a Solution Rate of Heat Absorbed = Q/t = mcΔT/t = (2.15*4.2*21.5)/(2*60*60)...
  9. M

    Photoelectric absorption in semiconductors

    Hi everybody. I'm new here and, first of all, sorry for my bad english :-D I'm studying photoelectric absorption in semiconductors. The book (and professor too) says that, in the conservation law: ki + kph = kf (where ki and kf are wave vectors of initial and final electron state, and...
  10. F

    Saturated absorption: decrease size of material rather than intensity of light?

    In saturated absorption, the decrease in absorption (and corresponding increase in wave transmission) is dependent on the intensity of the incoming wave. But why can't we decrease the size of saturable material, rather than the intensity of light? According to my understanding, saturable...
  11. F

    Saturated absorption: instanteneous, or does it produce lasting effects?

    In terms of saturated absorption of EM waves, is the following correct?: The material only has so many atoms that can absorb photons, so if there are more photons that there are atoms, the atoms cannot absorb all the photons, and thus a certain percentage of the photons pass through. OR...
  12. J

    Optical absorption liquid vs solid

    I'm looking for information about absorption of light per unit (atom, molecule, stoichiometric) in a liquid vs solid. For instance, imagine a unit cube filled with a saturated solution of, say, potassium permanganate, and shine a laser beam through it from bottom to top and measure the...
  13. D

    Calculating Cross Section from Neutron Absorption in a Gold Foil

    Homework Statement In an experiment carried out with a beam of thermal neutrons it is found that on traversing a 2mm thick foil of 197Au, some 70% of the neutrons are removed. What is the total thermal neutron cross-section for this isotope of gold? (Density of gold: 19300 kg m-3) Homework...
  14. G

    Help please -- Li saturation absorption spectroscopy

    Dear PF, I'm a graduate student working in an ultracold atomic phys lab. We're trying to build a new machine with Li6 as one of the components, but in order to cool it we need to do saturation absorption spectroscopy on a separate stand-alone cell in order to tell our lasers what frequencies...
  15. S

    Medical Aspirin absorption in stomach and intestine is confusing.

    Hello everyone, Aspirin(acetylsalicylic acid) is a weak acid. So in the acidic PH of stomach it must be more in nonionised form. In the alkaline PH of intestine it must be more in ionised form. Now my note says something is more absorbed if it is in non ionised form, this makes sense because...
  16. Z

    Mass absorption coefficient of aluminium

    I was conducting an experiment, and we had to use a radioactive source and a Geigor counter, in conjunction with aluminium plates. Using the data we produced we had to graph an absorption curve and obtain a value for the mass absorption coefficient of aluminium. Then we had to compare this...
  17. G

    Relation between absorption and refraction

    Hi All, this is puzzling me; we have a real part of the refractive index that governs refraction, ie. scattering, and we have an imaginary part, which describes the absorption of the light. The two are related, as you would expect, and a mathematical relationship exists between the two. The...
  18. H

    What is the heat absorption of apples in a hot water bath?

    I have a problem here I am trying to solve for work. Does not need to be 100% accurate. Apple slices are pushed through a bath of hot water to heat the outside of them for 30 seconds. - Apple slice has an area of 3500mm² = 0.035m² - Apple temperature is 3 degree cel - Hot water temp = 53...
  19. A

    Questions about light absorption

    why most material absorb EUV-region light? why hard X-ray can go through all material? 【http://galileo.phys.virginia.edu/classes/252/black_body_radiation.html】← here doesn't explain that. Thank you!
  20. L

    Emission or absorption spectrum

    Homework Statement X rays give continuous spectrum and line spectrum. Whether these spectrums are emission or absorption spectrum? Homework Equations The Attempt at a Solution I think it is emission spectrum, because there is no absorbing material. Still, i need confirmation from...
  21. H

    Infrared absorption spectrum of CO2 at 4,3 µm

    Hello! I'm writing a thesis about the optical properties of CO2. However I'm having a hard time finding any solid material about the basic info of the absorption spectrum of CO2. I'm especially interested in the absorption band at approximately 4,3µm. If any of you guys know some good articles...
  22. S

    Absorption Lines from discrete energy

    I know that an atom "absorbs" a particular frequency of energy depending on which element and which electron in this element. The question is (for example) if we take one known emission frequency from a particular element, and use that exclusively to bombard another element for a lower...
  23. G

    Absorption of Light: IR, Visible & Hydrogen Atom

    hi i am a little bit confused right now. i just read wikipedia about IR-spectroscopy and it is said, that: "In order for a vibrational mode in a molecule to be "IR active," it must be associated with changes in the dipole. A permanent dipole is not necessary, as the rule requires only a change...
  24. N

    Rhodium Thermal absorption cross section.

    Rhodium has been measured and the following values have been obtained for the resonance parameters of a well-isolated resonance Eo=1.26 ev , σo=5000 b , Γ = 0.156 ev , σs=5.5 b , Is there anyone can help me HOW to calculate the thermal absorption cross section ? I'm disparate I don't know how to...
  25. J

    What Are Emission and Absorption in Physics?

    emission and absorption?? confused! hiii, I am just wondering if anybody can give me a very simple definition of each of the two terms, and what the main difference is. Is emission when a wave enters a denser medium (from air to water)? and absorption when a wave enters a medium of lower...
  26. G

    Does an Electron Attract or Absorb a Photon?

    An electron absorbs a photon. Can this be termed as attraction of some kind?
  27. J

    Prove Absorption Law: A U (A and B) = A

    Homework Statement Prove the absorption law A U (A and B) = A Homework Equations The Attempt at a Solution I need to prove the sets are equal. I don't know how to prove the right hand as a subset of the left hand. For left hand as subset of right hand, it's pretty simple (we can define...
  28. Y

    Gas-liquid absorption design problem

    Hey everyone i'm in the process of designing an absorption tower (packed) to remove pure CO2 from a natural gas stream flowing at 25 MMscfd. The natural gas contains 8% CO2 initially, and must contain 3% CO2 on exiting the tower. The feed gas inlet conditions are 298K and 6900kPa...
  29. G

    Continuous Absorption of Energy by Chlorophyl

    hi i was thinking that after the laws of quantum mechanics, where all atoms and molecules have discrete energy states, things like continuous spectrums should be forbidden. but why are there still molecules like chlorophyl which show this property? i would think, that this means, that the...
  30. P

    Negative absorption peak in FTIR

    What does it mean if one found negative absorption in uv-vis absorption graph?
  31. A

    Reverse saturable absorption. Rate equations.

    Hello to all. Nice forum. Really like it. I hopee you'll can help me. The rate equaition in the case of reverse saturable absorber, with a long-lived strongly absorbing excited state (T0) which is rapidly populated from a ground state (S0), are given as: \frac{dS_{0}}{dt} = - \sigma_{01} S_{0}...
  32. G

    Absorption of Photon: Electron Constituents & Attraction

    How is a photon absorbed by an electron? Do the constituents of an electron have any role to play in this? Suppose the edge (boundary) of a photon approaches the edge (boundary) of an electron ( this image is just for convenience). What happens next? Does some kind of attraction develop...
  33. L

    Continuous absorption spectrum - why this happens?

    Continuous absorption spectrum -- why this happens? Homework Statement A pure green glass plate placed in the path of light, absorbs everything everything except green, similarly red glass plate absorbs everything except red. Homework Equations May i know the reason for this? Thanks...
  34. L

    Continuous absorption spectrum

    Homework Statement While dealing with continuous absorption spectrum, my book depicts like this " A pure green glass plate when placed in the path of white light, absorbs everything except green and gives continuous absorption spectrum" Homework Equations The Attempt at a Solution...
  35. D

    Specific absorption/ emission

    This is my understanding; please, correct me if I'm wrong. If you bombard an atom with em-waves they will never break loose electrons until a certain threshold frequency. At this point the intensity of the light (or the amount of photons) striking the atom is proportional to the number of...
  36. A

    Absorption and solar radiation spectra

    Hi, I'm hoping someone can advise me on the best place to find the absorption spectra for water (fresh) and ice, for the wavelength range UV to IR. Also, I'm looking for the solar radiation spectrum at the surface of the Earth (i.e. after atmospheric effects have been taken into account)...
  37. chaszz

    What is electron emission or absorption of a photon?

    What is meant when it is said that an electron emits or absorbs a photon (leaving aside the aspect of heightened or reduced energy states and orbit changes, which I understand.) ? I see four possibilities: 1. Whether the electron is a particle or a wave or some combination of the two, the...
  38. A

    Help on Sound Absorption Coefficient Calculation

    Hello all, I come from musical sciences, but I'm trying to learn something about acoustics, so here I am, asking for some help about the impedance tube sound absorption coefficient test. I have and impedance tube, two microphones technique (ISO 10534-2), B&K microphones connected to the...
  39. M

    Thermal Radiation v Absorption of Light

    A layman with an interest in quantum mechanics here. Just want to check I understand something... Is the phenomenon of electromagnetic waves being emitted by an atom due to it being hot (black body radiation) different to that of such waves being emitted as a result of absorbing light...
  40. J

    Does the CMBR have a detectable absorption spectrum?

    I posted this http://answers.yahoo.com/question/index;_ylt=AioiPKUALWyrKuH4dGXejba9DH1G;_ylv=3?qid=20110618143816AAgRMyF"on Yahoo Answers yesterday, but it might be too specialized: If I understand correctly, the Cosmic Microwave Background Radiation is a perfect thermal (black-body)...
  41. E

    Question about interpreting absorption cross sections

    Hi everyone, I was wondering if I can get a little help interpreting absorption cross sections. I would like to figure out how long I would have to shine a particular light on a monolayer of molecules to expect an appreciable fraction of isomerization. Here is how far I've gotten so far...
  42. C

    Automotive Automotive application for absorption cycle?

    Hi there, I joined specifically to ask for help in exploring the possibility of harvesting the waste heat from a cars engine and recycling this energy to improve the engines efficiency. I'm assuming most people know about thermo dynamics, internal combustion and volumetric efficiency...
  43. E

    Atmospheric Gases - absorption, reflection, and emission of radiation

    I'm going to be very careful to avoid the word "greenhouse" because of the indefinite ban on discussions about climate change - I want to be clear, this isn't a topic about that. Part 1 - some gasses in the atmosphere absorb and emit radiation in the thermal infrared range. Gases like water...
  44. MTd2

    Hydrogen absorption capabilities by transional metals.

    I know about the typical case of Paladium, which is said to "absorb 900x its volume in hydrogen". But this is completely vague. I'd like to know more about the theory of absorption as well as of other materials, like Nickel, Niobium and other transitional metals. Would someone, please, give me...
  45. J

    Quick question about neutron scattering and absorption cross sections

    Does the absorption cross section to scattering cross section ratio of an isotope vary with neutron energy or stay constant? I have heard that cross sections in general are inversely proportional to velocity (eg the fission cross section of U235 is about 1000 times higher for thermal neutrons...
  46. M

    Beer-lambert law and UV absorption spectroscopy.

    In a flash photolysis experiment, the time dependant concentration of [OH] was measured by UV absorption spectroscopy at around 308 nm, where the effective molecular absorption cross section σ = 4.13*10^-16 cm^2. Using the beer lamber law calculate the concentration (number density) of OH...
  47. A

    How does neutron absorption turn uranium into plutonium?

    I keep reading that when a U-238 atom absorbs a neutron it turns into Pu-239. How does that happen? If I'm not mistaken Pu-239 is U-238 plus 2 protons and 2 electrons and minus 2 neutrons. When U-238 absorbs the neutron and becomes U-239 I can see that it can turn into Pu-239 if 2 neutrons decay...
  48. S

    Absorption spectra of molecular hydrogen

    I've been looking everywhere for information on the absorption spectra of molecular hydrogen. I need some pretty exact numbers. If anybody can point me in the right direction it would be greatly appreciated.
  49. B

    What is undamped vibration absorption ?

    What is “undamped vibration absorption” ? What is “undamped vibration absorption” and how would you use this concept to absorb the vibration of a un-damped, simple mass spring system of mass m and stiffness k oscillating at its resonance frequency?
  50. B

    Calculating Sun Temperature from Tank Heat Absorption

    Lets take this specific example: Sun is radiating heat and a water tank with a certain surface area S absorbs this heat. Sun rays are perpendicular to this tank. [PLAIN]http://pokit.etf.ba/get/778c2978a453178481d142a891ae07c5.jpg If I know much energy did my tank of water...
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