Spectra Definition and 285 Threads

So I've been self-studying from Griffiths Intro to QM to get back in shape for graduate school this fall, and I guess I'd just like some confirmation that I'm on the right track... So while I am sure there are many other applications, the one I am dealing with is eigenfunctions of an operator...

Homework Statement In rotations of diatomic molecules such as HCL, the hamiltonian is found to be: \hat H = \frac{\hat L^2}{2\mu a^2} where ##\mu## is the reduced mass, a is the separation. (a) Find the energy levels and separation. (b) Explain why rotational spectra of HCl...

I'm trying to understand the form of the absorption spectrum of a T=0K intrinsic semiconductor. The valence band/conduction band energy diagram looks like; http://postimg.org/image/wyzvo9lsr/ As E = \frac{\hbar^2 k^2}{2m^*} where m^* denotes the effective mass. The image doesn't...

We've been assigned Griffiths QM for undergraduate physics. I don't particularly like it, but anyway. It says that if the eigenvalues an observable are continuous then the eigenfunctions do not represent physically realisable states. So the eigenfunctions of the hamiltonian are discrete and...

Homework Statement For a silver atom, energy corresponding to Kα transition is 21.75 KeV. Also minimum energy of a striking electron so as to produce L X-Rays is 3.56 keV. Now, if electron with an energy of 23 keV strike a silver target the characteristic X-rays spectrum will have a)only kα...

I don't really understand the explanation given in Binney's text about: Hamiltonian is given by: H = \frac{\hbar^2}{2} \left( \frac{J_x^2}{I_x} + \frac{J_y^2}{I_y} + \frac{J_z^2}{I_z} \right) Orient axes such that ##I_x = I_y = I##. H = \frac{\hbar^2}{2} \left( \frac{J^2}{I} +...

Hi, I am looking for online molecular emission spectra database for spectroscopic analysis of plasma. It would be great if searching in it is based on a wavelength of spectral lines/bands. For atomic spectra I found this database: http://physics.nist.gov/PhysRefData/ASD/lines_form.html But I...

I need help understanding the relationship between the excitation and emission spectra for a fluorescent material. This is not homework. Let's say we have the following graph which plots the two spectra for a given material: Two curves are shown - the excitation spectra and the...

I'm currently doing some research at the moment for my professor, and he gave me a list of things to look at. Before he had me calculate the "real center of mass cross section." Now, starting at point 0 for publication, he's having me go through and do some other things. In his list of things to...

I was given a sample, that it is suppossed to be a medium thickness Rhodium on top of an infinite silicon waffer. The experimental RBS spectrum along with the simulation looks like that Apparently, there is another element(or maybe 2) that appear on the experimental spectrum. I am relatively...

Quick question: I keep seeing the following terms in my reading on nuclear magnetic resonance: - Spectral linewidth - Spectral bandwidth - Signal bandwidth Are these all qualitatively different terms? Or are they more or less referring to the same thing?

Homework Statement A photon emitted during an electronic transition in a hydrogen atom has a wavelength of 486.2 nm. From what initial energy level (ni) did the electron transition? Homework Equations Energy = hc/wavelength (h = Planck's constant; c is speed of light; and wavelength is 486.2...

Hello fellow physicists, I have a query about a practical matter. I'm trying to simulate the rotational spectrum of a symmetric top and so far I've been able to produce a stick spectrum of it. My first problem is that the lines do not exactly match the positions of the peaks but my biggest...

Preferably I would like to find a UV-VIS absorbance spectra of urine. I have found ones that focus on the deep UV range, and one that had fluorescence peak information. Any help would be appreciated.

Hello, Something I have some time wondering and still couldn't find the answer is to this question: if there is some relation between the Spectrum (functional analysis) and the Frequency spectrum in Fourier Analysis. Now that I think about it there seems to be a casuality the use of the...

Can we measure the band energy gap from Fluorescence spectra? If yes, in what way? the excitation spectra or the emission spectra or both Is there a good reference on this subject specifically :smile:

Hello, am working with luminescence spectra, including excitation and emission spectra. When you makes an initial characterization of a sample should be done first? an absorption spectrum? At what wavelength excitation should be performed to see the desired effect? Particularly when...

I have some questions regarding thermal radiation spectra of different objects. Is thermal radiation of objects due to electromagnetic radiation alone? Does my desk which is at room temperature emit as a blackbody with the proper factor for emissivity? Where is the "cavity" that the radiation is...

Hello all, What is mean the Ritz Wavelengths in the NIST Atomic Spectra Database? Why the Ritz or Observed value for some Wavelength are very different? Thanks, Lil

Hi Can anyone point me to a clear description of line mixing/"cross-relaxation" in atomic/molecular spectra? Every paper I read assumes some previous knowledge, is there an online resource that will explain why two transition would mix? I'm specifically looking for conceptual explanation...

Hi, I have measured conventional absorption spectra of semiconductor - Optical density from wavelenght. So now I want to evaluate band gap for this material. In what kind of coordinates I how to reperesnt this spectra to see the band gap value ( where graph crosses the Energy axis) ? *I m...

IR and NIR spectroscopy usually employ Fourier transformation to separate the signal into individual wavelength, UV and Vis spectroscopy normally apply gratings for light dispersion (into individual wavelength). What is the cutoff wavelength, and why is so?

Not sure how to go ahead with this problem: Hydrogen atoms in a sample are excited to n=5 states and it is found that photons of all possible wavelengths are present in the emission spectra. What would be the minimum no. of hydrogen atoms in the sample? (sorry got nothin buzzin to attempt this...

Hello everyone! I´m new to the forum and to start participating and being part of it I have the following problem and question: I began using a dispersive Raman system and I got spectra of Rhodamine B and heparin sodium (and anticoagulant and glycosaminoglycan) in solid form and the spectra...

We're just been learning about emission and absorption spectra and how these relate to the energy levels of electrons in an atom but its brought up 2 questions. 1. In chemistry our notes say that the energy change between levels gets smaller as you move out from the nucleus, however in...

Hi all I was reading this paper about spectral clustering: Ng et all. (Nips 2001) http://ai.stanford.edu/~ang/papers/nips01-spectral.pdf Short question: What is the connection between the eigenvalues of a Laplacian? Long question: I got stuck on why the process makes sense...

I understand that light travels at “c” through any medium, and that the apparent slowing results from the absorption and re-emission of the photons by atoms in the medium. If this is the case, why, for example, are astronomers able to see the emission/absorption spectra of distant stars...

CO2 is supposed to create a "doublet" peak at 2350 cm-1 according to my IR correlation chart. Why is this doublet created? As DrDu explained in my previous post, two peaks are seen for the N-O bond because it has IR-active symmetric and asymmetric stretches. But CO2 is a linear molecule, and...

My IR spectra correlation chart for organic chemistry says that the stretch for a nitro N-O bond occurs at "1550 and 1400cm-1" and that it will look like "teeth". Why does N-O have two peaks? The rest of the functional groups on my chart list a range in which a single peak should appear, but why...

Homework Statement In a particluar x-ray tube, an electron approaches the target moving at 2.35 108 m/s. It slows down on being deflected by a nucleus of the target, emitting a photon of energy 40 keV. Ignoring the nuclear recoil, but not relativity, compute the final speed of the electron...

We can know about distant stars temperature,its elements etc by observing its spectra... But that star has a velocity related to us... The spectra will be shifted... Then how do we know the correct spectra? Another ques... Suppose, something emits a X ray... Then will its characteristic will...

I am measuring a 2D turbulent flow using a split film probe. This gives a time history of the velocity in the x and y directions. I have a few questions about obtaining energy spectra from these measurements that I am hoping someone can help me with. The energy spectrum of the turbulent flow is...

A student collects diffraction data using a lamp with known emission wavelengths of 425nm, 565nm, 600nm, and 700nm. These lines appeared on her spectroscope at 32mm, 59mm, 63mm, and 69mm (all measured from the same arbitrary 0mm position). With these data she is able to calibrate her...

hi everyone! does a general Rydberg-like formula exist to predict the emission spectrum wavelengths of any atom? if not, why?

Been viewing this site for a while now and very much appreciate all the contributors! I can't seem to find an answer to this anywhere so I think I may be misunderstanding the basic ideas of absorption and emission spectra... An absorption spectrum, say of our Sun, is as I understand it the...

Homework Statement Okay, I'll start off with a summary of the practical. And then the question. The aim was to measure the wavelength of yellow light from a sodium vapour lamp, using a telescope and a diffraction grating of 300 lines per mm. The instructions tell us to prepare the apparatus, so...

I recently performed an XRF spectroscopy on a metal foil in a materials lab for school and I;m having trouble reasoning out an answer, though it's probably an easy one. The idea behind the lab is, we are given a bi-metal foil, which is either an alloy or a "sandwich" of two thin sheets of metal...

Homework Statement Although H-atom contains one electron yet we get a number of lines in the spectrum of Hydrogen. Why??

Hi there, my comparatively ignorant mind is wondering, When an atomic transmutation occurs all of the quantum levels of the new atom also change 1) what is the actual rate of this change? would a nonplayer "observer photon" passing near the suddenly different element note the quantum level...

Hello, I can't seem to find a comprehensive explanation for this recurring phenomenon on my XRF spectra graphs. It's a high intensity peak that occurs seemingly below the 0 keV energy mark. And it seem to be common to many graphs, yet nowhere seems to say what it actually is, aside from a...

i understand that a good black body would produce a plank curve. it is my understanding that plank curves are continuous emmision spectra.. now the sun a good approximation to a black body... but we get and emission/absorbtion spectra.. can you please help me understand where i am going...

So I have an assignment due in tomorrow night that I've been working on recently and I find myself with a question. Because our software was playing up it wouldn't give us the correct algebraic relation to calibrate our results, so I've had to manually do this. From the three sources we were...

Hello, I recently did an experiment where I examined and analyzed crystals using SEM-EDS. One of the major parts of my experiment was to determine the concentration of a certain element (calcium) in the different crystal samples. I noticed that some calcium peaks were higher than others. Does...

Homework Statement Adjacent wavelengths 251.1 nm and 238.6 nm are found in one series of transitions among the radiations emitted by ionized helium. 1.) Find the value of n0 for this series: Possible answers: n0= 1, 2, 3, 4, 5 2.) Find the series limit: Possible answers: λlimit= 91.13 nm...

The lifetime of the 32P1/2 to 32S1/2 transition of the Na atom at 5896 angstrom (one of the Na D lines) is measured to be 16.4 ns. What are the einstein a and b coeff? What is the transition moment in debye? What is the peak absorption cross section for the transition in angstrom2, assuming...

What are the top bio signatures we should be looking in exo planet spectra? What sort of telescope would be needed to obtain good spectra of potential Earth twins? Would it require Darwin or TFP or could something cheaper obtain such spectra?

Hello, I've simulated the output of a x-ray tube using a software (spekcalc). In my simulation the energy range is 17-170 keV, the air thickness is 1m and there is 1.5 mm of Al. The mA value is 1 (default value). After the estimation I obtained a characteristic spectra: in y there is the...

Hello, PF. I'm a simple high school student who likes a challenge, and as such, I decided to put together a research project involving reading spectral lines from photographs I took. I got the lens, I got the camera, I got pictures, and now I'm stumped. Reading up on Rpsec, a lot of it's...

I understand that having a periodic signal x(t) we can find a signal y(t) which uses harmonically related exponentials in order to construct the x(t) signal each exponential has a frequency and magnitude, for example 3*e^{j 2 \omega} has a frequency of \frac{2 \pi}{2 \omega} =...

Hi everybody, I'm reading about digital modulation (in particular on Lee-Messerschmitt's Digital Communications) and I have this picture (RX.jpeg attached). These three structures are equivalent: so, at the end of each structure, I should have the same spectrum. I tried to think what can...