What is Spectroscopy: Definition and 332 Discussions

Spectroscopy is the study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation. In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum; indeed, historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of physics, chemistry, and astronomy, allowing the composition, physical structure and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances. Important applications arise from biomedical spectroscopy in the areas of tissue analysis and medical imaging.

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  1. S

    Why Do Different Electron Transitions Emit Different Spectral Lines?

    The emission spectrum of an unknown element contains two lines - one in the visible portion of the spectrum, and the other, ultraviolet. Based on the electromagnetic spectrum and Neil Bohr's model of the atom, account for the difference in energy between these two lines. I'm having a bit of a...
  2. fsonnichsen

    Does increasing slit size in spectroscopy affect SNR?

    Anyone know a source for a mathematical analysis relating the slit-size/throughput for a spectrometer vs SNR? I find that I always get better SNR (but not necessarily resolution) with a wider slit or higher throughput monochromator when doing emissions work. Fritz
  3. H

    Mass Spectroscopy: Difference in potential

    Homework Statement A Mass-spectrometer consists of cylindrical capacitor with inner radius R1=4.5 cm and outer radius R2=5.1cm. Ions enter the mass-spectrometer through a narrow slit which is situated in between the capacitor plates as shown on the picture. Uniform magnetic field B=0.4 T is...
  4. L

    Raman spectroscopy: data analysis: convolution

    hey guys, i hope you can help. my task is to analyse data of raman spectroscopy. therefor i have to deconvolute it. that means the data must have been convoluted somewhere. is it true that the raw data which i receive is convoluted already? or is it common to convolute the data "active"...
  5. O

    Kirchhoff's Three Laws of Spectroscopy

    Kirchhoff's Three Laws of Spectroscopy are as follows. 1. An incandescent solid, liquid, or gas under high pressure, emits a continuous spectrum. 2. A hot gas under low pressure emits a "bright-line" or emission-line spectrum. 3. A continuous spectrum source viewed through a cool, low-density...
  6. J

    (long) question - Raman, IR spectroscopy; virtual energy states, light; heat

    I'm confused about what is going on theoretically with Raman, and light in general, wrt photon absorption, annihilation, and re-emission; I don't have the math background to understand Fourier transform, of anything past simple algebra anymore, but would like to at least have a decent...
  7. 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...
  8. S

    IR Spectroscopy: Examining Absorption of Water, CO2 & Methane

    I've been doing IR spectroscopy to examine to the absorption spectrum of water and carbon dioxide, after which I took another absorption spectrum with a methane gas cell. The absorption spectrum without the methane shows absorption from carbon dioxide around 4000nm, however, this is not apparent...
  9. N

    Two-Pulse Ramsey Spectroscopy: Resources for Niles

    Hi Does anybody know of any good papers/texts explaining this concept? I am mainly looking for two-pulse RS. Niles.
  10. L

    X-ray absorption spectroscopy - fine edge structure

    Hi, could someone tell me how the fine edge structure next the the absorbing edge in an XAS arises? from my understanding an XAS is a plot of absorption coefficient against energy of incoming xray. The absorption edge is at an energy corresponding to when the energy is just sufficient to...
  11. S

    (SPECTROSCOPY) chromium(III) absorb light

    Homework Statement Why does chromium(III) absorb light? Explain what is happening on an atomic level. -> I don't really get this problem. Can you help me out...? Please... Homework Equations The Attempt at a Solution
  12. F

    Cosmic Expansion - Spectroscopy Experiment

    Astronomers tend to presume that between any given source and observer, all light travels the same distance at the same speed. But light bends in the presence of gravity. Observe a simple prism and you will note the red wavelength bends less than violet. Forget stars and planets, how many...
  13. S

    Velocity of a star for Doppler Spectroscopy

    Im trying to solve back for Jupiters effect on the suns orbital velocity. I've looked up the asnwer and its 12.7 m/s and the formula I have for this is http://en.wikipedia.org/wiki/Doppler_spectroscopy v = SQR (Gm*/r) where G is Grav constant M is the mass of the star (planets mass is...
  14. S

    Simple Alpha Particle Spectroscopy Question

    Homework Statement When detecting alpha decay with a spectrometer, why is it important to evacuate the chamber to create a adequate vacuum for where the source is place? Why is it better to place a radioactive source underneath a detector facing up rather than above the detector and facing...
  15. L

    Help to fully understand a podcast about spectroscopy

    Homework Statement I've recorded an extract of a radio podcast (from Chemistry World) which deals about spectroscopy. But there are a few points missing in my transcription (I'm French) Here it is : http://vfsilesieux.free.fr/spectroscopyaudio/audio.swf I have called (1) to (6) the...
  16. W

    Fluorescence and Raman spectroscopy

    I'm currently working on a lab that is exploring the Raman effect. One of the suggested exercises was to record the raman spectrum (from a mercury lamp through CCl4) around the rayleigh peaks at 435.8 nm and 404.7 nm. For the former, my results were fairly consistent with what I expected in that...
  17. M

    Raman Spectroscopy: Understanding Intensity & Wave Number Peaks

    Tell me what do the peaks in the graph show which is b/w Intensity and wave number in raman spectroscopy ? Are the peaks due to transition from a grnd state to an exicted state or vice versa , low energy are stokes and high energy are the anti stokes one
  18. H

    Microwave Spectroscopy - Obtaining info when isotope absorptions are known

    Heres the question [PLAIN]http://img213.imageshack.us/img213/2669/16772870.jpg I know that I'm supposed to derive these values from the fact that I know the absorptions of 2 different isotopes of the diatomic molecule but I don't know how to go about doing it. I can obtain the masses of...
  19. I

    Density of states and Raman spectroscopy

    Hello everyone Lately I am taking some problem with my thesys, I am not an expert in theoretical physics but not bad as experimetal. I want to calculate the contribution of the w(q) away from zone O ob Brillouin to fit my experimental data to the theory and to know if the quantum theory work...
  20. P

    Raman Spectroscopy Exposure Time

    When you are setting up a spectral acquisition with a raman microscope, what does the exposure time mean? I would expect this to mean the amount of time the sample is exposed to the laser, but it doesn't seem like that can be true if it takes around 20 minutes to acquire the spectrum with a 2...
  21. T

    Alpha Spectroscopy Low Energy Error

    Hello, I've taken a spectrum of a U238 sample, and I keep getting this hill of low energy values. Any ideas as to what could be causing them? Sorry about the weird screenshot; it's the only one I had and my friend couldn't see the dots, so i had to go over them in paint.
  22. A

    Spectroscopy and Russell-Saunders coupling

    So, this has been bugging me for years (seriously). So my spectroscopy course says the following: 1) In an atom, for a closed subshell, for each electron possesing an m_l quantum number there is another electron possesing -m_l, which means that the sum M_L = \sum {m_l} = 0. I have no problem...
  23. I

    Update Ammonia Spectroscopy Data: Delta0, Delta1, Delta2, x_c, V_c, E_d

    I need updated data about ammonia. I have consulted some papers and handbooks but the information I found is incomplete or outdated, particularly about the VARIANCE of the measurements. Essentialy, I need the following data: delta0 - the difference between the two first states delta1...
  24. C

    Gamma Spectroscopy: NAI vs Germanium Detector Accuracy

    What is a difference between NAI and Germanium detector in terms of accuracy?
  25. C

    Protein Dynamics By Raman Spectroscopy

    Can one monitor dynamics of a specific protein domain (helix, strand etc) by Raman Sp? If one labels a specific residue with an isotope, like in NMR, can one use that to monitor the dynamics of the region that encompasses this residue?
  26. D

    Heisenberg Principle in Context of Absorption/Emission Spectroscopy

    Why do we get line spectra from absorption/emission of atoms, but band spectra from absorption/emission of molecules? As I understand the Heisenberg Uncertainty Principle mathematically, some operators do not commute and as such, the order of measurements determines the results. In regard...
  27. C

    NMR Spectroscopy: Butane in Magnetic Field & Hydrogen Alignment

    When a molecule, let's say butane is placed in an external magnetic field and its hydrogens align parallel or antiparallel to the direction of the magnetic field, do 50% of the H atoms align parallel to the B field and the other 50% align antiparallel or what? If so, when they radio waves are...
  28. T

    Fluorescence Spectroscopy Q?

    1. Homework Statement calculate the angle between the absorption dipole and the emission dipole of specific blue maleimide ? limiting polarization was determined to be 0.5 and anisotropy 0.4 Relevant equations I know from lectures that the angle should in fact be zero because the actual max...
  29. A

    What Can Photoelectron Spectroscopy Reveal About Surface Structure?

    hi, i went through some textbooks about photoelectron spectroscopy and was looking for information on how it is used to determine the structure of a surface. but they mostly focus on how it can be used to identify the identity of the sample and some of the terms in the books were too...
  30. mccoy1

    Discover the Best Book on Raman Spectroscopy - Expert Recommendations

    Please can anyone suggest a good book on raman spectroscopy. cheers.
  31. S

    Raman Spectroscopy: Stokes and Anti-Stokes Wavelengths

    Hi, For someone my question could be very simple but I couldn't find a well explain paper that explain this to me. In a Raman spectrometer the stokes and anti-stokes wavelength will always be grater than the laser wavelength used?. I have this confusion because I saw that Raman...
  32. J

    Detecting hydrogen gas via IR spectroscopy

    Say I want to monitor the interface of an electrochemical cell via IR spectroscopy. If H2 gas is generated, there must be a characteristic IR signature to this event. How can I figure out what this is? Are there calculations for this? I'm sure this is in the literature somewhere, but I...
  33. M

    Basic IR Spectroscopy and dipole moments

    Hi Why does a bond stretch or vibration have to cause a change in dipole moment to be IR active? Presumably all vibrational modes depend on energy aborption to occur whether they cause a change in dipole or not. I'm presuming that only those vibrational modes that cause a dipole change are...
  34. M

    Hydrogen Spectroscopy: 2S-2P Lamb Shift Transition Frequency

    I'm looking for the more precise value for the 2S-2P lamb shift transition frequency. I found the value 1 057 844.0(2.4) kHz in the National Institute of Standards and Technology website: http://physics.nist.gov/PhysRefData/HDEL/transfreq.html. Can someone tell me if there is a better value...
  35. M

    Proton NMR & Analyzing NMR Spec - What to Do?

    Hi Are there any protons that do not show up on proton NMR as I am analysing an NMR spec (of a known molecule but I don't know what it is!) and I can't get my integration to equal the number of Hs in the empirical formula of the molecule Many thahks
  36. M

    UV Spectroscopy - Absorbance vs transmission

    Hi In UV spectrscopy, is the definition of absorbance (A = ecl) derived from the definition of transmission (T = It/Io) where It is the transmitted light and Io is the incident light, or is the definition of transmission defined from absorbance. Also A = -log(T) and T = 10^-A = 10-ecl...
  37. M

    What units does incident light have in UV spectroscopy

    Hi What units does incident light have in UV spec? Is it joules? Transmission is defined as transmitted light / incident light so any units of light simply cancel out to give a unitless number. I presume the original units were joules as light is EMR? Perhaps its more complicated than that...
  38. M

    Why Don't All Molecular Vibrations Lead to Observable Infrared Absorptions?

    Hi I'm a little bit confused about infrared spectroscopy. My basic understanding (which was obviously wrong) was that molecules absorbed EMR in the infrared region and that this caused vibrations in the molecule. Some vibrations/stretching cause a change in charge distribution and for reasons...
  39. F

    Laser Induced Breakdown Spectroscopy

    my question is why oxygen lines does not appear in metal oxides spectrum taken at 532nm wavelength of Nd:YAG laser at atmospheric pressure. and what is the criteria for selecting emission lines for analysis?
  40. E

    Organic Chemistry: NMR Spectroscopy concept question

    Why are sp2 carbons more downfield than sp3 carbons? Is it because the bond length of sp2 carbons is shorter (electrons are more localized-thus more shielded)?
  41. S

    Simple Spectrometer and Spectroscopy Question

    Homework Statement Two first-order spectrum lines are measured by a 9650line/cm spectroscope at angles, on each side of the center, of +26*38', +41*02' and -26*18', -40*27'. Calculate the wavelengths based on these data.Homework Equations \lambda= (d/m)sin(\theta) The Attempt at a Solution i...
  42. J

    Reflection loss during absorption spectroscopy

    An isotropic solid has a refractive index of 10 at low frequencies. A 10 um thick platelet of this solid with perfectly polished planes shows two absorption bands in optical transmission. These bands, corrected for reflection, have a (negative) Gaussian shape. They occur at frequencies of 3x1012...
  43. P

    Plasma Spectroscopy, H.Griem

    Can anyone help me find this book: Plasma Spectroscopy, Author: (H.Griem) It is the most famous book and it is the very basic level of plasma spectroscopy, if you find it that will be great for everyone in this field. thank you
  44. C

    Raman Spectroscopy graph question

    What are some simple graphs that can be created (in Matlab) relating to Raman Spectroscopy or just basic equations that can somehow be related to it? So far all I've done is graph E=E_0 cos (wt + 1/2 αt^2). And any suggestions of things I should read up on about the topic and understand...
  45. N

    Raman spectroscopy amide I processing

    Hello Group! I'm working on analyzing Raman spectra of proteins. I'm particularly interested in learning more about the signal processing of the amide I band. If anyone has any experience with Peakfit program or Origin, Savitsky-Golay smoothing, or amide I deconvolution for secondary...
  46. N

    Mossbauer Spectroscopy, velocity conversion

    i have a mossbauer data for a ferrite sample in terms of channel vs counts, i need to convert it into velocity vs counts. i don't have any software, i tried to download the demo versions of MOSSWIN and IGOR PRO but i am unable to know how to convert them. Please guide me for the conversion.
  47. C

    Raman Spectroscopy, A Few Questions

    Using a PMT/Monochromator, we have Surface Enchanced Raman Vials we are using to analyze samples. One thing I am trying to figure out: The so called finger print region is 500-3000 wavenumbers after the wavelength of the laser you are using. In our case, we are currently using a 200mW 532nm...
  48. Q

    Spectroscopy via diffraction gratings with different spacings

    What's the difference when I observe the emission lines of say, Hydrogen or Neon, on two diffraction gratings having different line spacings? Will there be colors that will only be observed in one and not the other? Thank you!
  49. C

    Internet Journal of Vibrationsl Spectroscopy

    Hello, Gentlemen! Is there anybody who has ever published in the "Internet Journal of Vibrational Spectroscopy"? I had a couple of article published there (in the years 1999 and 2000), and everithing with the site of the Journal www.ijvs.com was correct until approx. one week ago...
  50. Q

    Gamma ray spectroscopy: Germanium detector efficiency calibration.

    Hi all, Got a bit of a problem with a lab experiment at uni (I'm not sure if this is the right place to post this, mods feel free to move it if necessary!) Anyway: We're trying to get a plot of efficiency against energy for a planar germanium detector. We've got spectra for different...
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