Absorption Definition and 534 Threads

Hello , I was trying to calculate the effective absorption cross section ( group constant) of U-238 in the resonance region between neutron energies (1 ev - 10 kev) but as you can see from the picture U-238 has a lot of resonance at this region, I was wondering if there is a way I can obtain...

Yo does anyone have a table from like Brookhaven or somewhere of absorption cross sections for just about anything in the 1/v region? And have the precision included in the data. I'm doing a pretty quick statistics assignment.

When scientists analyze proteins (chains of amino acids), often times light spectroscopy is used. Light is passes through a cuvet containing dissolved protein, and the absorption is measured. My question is: How do bonds absorb energy? What is the actual mechanism? I have been told that the...

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...

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...

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.

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...

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...

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...

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...

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)...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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!

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...

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...

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...

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...

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...

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...

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

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...

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...

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...

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

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}...

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...

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...

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...

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...

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)...

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...

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...

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...

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)...

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...

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 I:-p...

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...

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...

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...

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...

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...