Spectra Definition and 264 Threads

I'd like to numerically calculate the power spectra of the scalar perturbation at the Hubble crossing in warm inflation, my problem is that I don't know how to do it. As I know, the Hubble crossing happens at the onset of warm inflation where the different modes become larger than the Hubble...

Hi all! I would have two questions, related to laser and photodiodes spectra. 1) We know that lasers produce a very monochromatic radiation, even if they are low to moderatly expensive. That is because the emitted frequency light is dependend on Ec - Ev = Eg which is the bandgap. So electrons...

I have some more detailed questions on this further on but I found it better to start with a very basic question first: If higher temperature is correlated with shorter emitting wavelengths, how come there are incandescent light bulbs that emit yellowish light but are hotter than incandescent...

If we assume that there is a fixed charged particle and another charged particle is spiraling down towards it, it emits electromagnetic waves as it is accelerated motion. We get a continuous spectrum. Now, if I allow the emitted photons to fall on a very photosensitive material, whose efficiency...

Homework Statement [/B] "Absorption spectra of gaeous HCl show a line at 3.5 μm which results form molecular vibration (oscillation from interatomic distance)" How do I get the frequency of vibration from this? Homework Equations ? If I knew this, then I could probably solve the problem The...

I've seen the equation I think is just for hydrogen. is this just for hydrogen? of course this doesn't return the atomic spectra, it returns the energy. So using E=h*v and Planck's constant. a simple factor of 1/h would return the frequency. right? Energy is directly proportional to frequency...

That pesky 3.5 keV line just won't go away. The authors note that it's compatible with dark matter composed of 7.02 keV sterile neutrinos. If such is the case, the Majorana mass scale of the seesaw mechanism needn't coincide with the GUT scale (if such a scale even exists).

Homework Statement Let \begin{equation*} f(t) = 2 + \cos\left( 3t - \frac{\pi}{6} \right) + \frac{1}{4}\cos\left( \frac{1}{2}t + \frac{\pi}{3} \right) + \sin^2(t) \end{equation*} Determine the period ##T## and fundamental frequency ##\omega_0## of ##f## and draw images of its amplitude and...

Hello Forum, I understand that an electron inside an atom/molecule has many possible transitions that it can make from a higher energy state (once it is excited there) to a lower energy state (possibly the ground state but not necessarily). For example, the electron can jump directly from...

thought this would be an interesting article; http://physicsworld.com/cws/article/news/2016/dec/19/antiatoms-yield-their-first-optical-spectrum

Hello A friend of mine asked me if he could improve the (amateur) characterization of minerals by studying the absorption spectra during the application of a magnetic field. I thought that maybe the electron cyclotron resonance could work, but then I noticed that very low temperatures are...

I'm not a molecular physicist, so my speculations are bound to be somewhat naive. I'm only hoping to initiate some discussion around the subject, which I thought might be interesting to all. Now that the electronic absorption spectrum of the atomic anti-hydrogen 1s->2s electronic transition...

I was reading this article which talks about the theoretical model behind blackbody spectra: http://www.cv.nrao.edu/course/astr534/BlackBodyRad.html At the start, it mentions standing waves in a cavity. Standing waves in this model consist of an integer number of wavelengths. The standing waves...

Is there any way to convert a continuous, aperiodic spectrum, to a discrete spectrum, in a signal? If so, would part of he energy of this signal be lost, I am this process of conversion, or would it be " distributed" amomg the various frequencies?

I have read that magnesium’s flame is white, and the light emitted includes all the wavelengths of visible light. Calcium, on the other hand, needs less energy to excite its valence electron, and hence, during emission, the radiation given off has a longer wavelength (red light) and its flame is...

A few quick questions I'd like cleared up:1) Alkali metals are said to have a really low threshold energy, enough for visible light to cause the photoelectric effect. Does this mean if I aim a flashlight (turned on) at a piece of sodium, I could ionise it? Simply flashing a light over a piece of...

Hi all, I am studying in Raman spectra and I don't know that what's means r^t a r =1. r^t is r transpose, r^t=(x,y,z). And a is diagonalized polarizability tensor. Whats means that is equal 1? Just normailzation? Help me,and so sorry my english is too bad...

When you heat things up, they emit specific wavelengths of light, right? Like when you heat up sodium, it emits yellow. But don't things emit shorter wavelengths of light at higher temperatures? Like how hotter stars are blue and colder stars are yellow. Since stars are mostly hydrogen...

Hi all, In an x-ray spectrum, the curve part represents the bremsstrahlung part, and the spikes are the characteristics x-rays. Characteristic x-rays represent a discrete energy. However, in many textbooks, I noticed that the characteristic x-rays are often represented as a peak, which implies...

Consider a piece of pure Fe hot enough to have a bright white color (about 2 000 ºC, e.g.) and the characteristic yellow narrow yellow emission of the Na atom. Does the Na yellow band will be present at the thermal spectra of the pure Fe? My guess: Yes.

Homework Statement Hi! I have a a question regarding the Atomic Spectra of Hydrogen and Mercury. My problem involves the value of m and Rydberg's constant. I used a spectrometer for this lab and calculated all the necessary angles. Homework Equations See below The Attempt at a Solution...

Hi everibody. I have been tasked with finding out the spectral tipe of two stars; for that, I have processed the spectres. You can find them in the links. http://postimg.org/image/5a6w2pbf5/ http://postimg.org/image/71iehdz4h/ Now, I am a little lost, I am clueless about where to look for a...

Scientists have measured both the blackbody spectrum and also the atomic spectra of various elements in the Sun. How do they distinguish between the two and filter out the light from either one?

This should be easy but I'm totally stuck here. So I'm calculating the Kβ line (emitted energy) of Molybdenum (Mo 42). I'm using Moseley's law and am moving from the M-shell to the K-shell. Recall Moseley's law is E = 13.6 eV (Z-σ)2 *1/n2. The effective formula for the energy emitted is thus...

I am seeing units for atomic/molecular spectra listed as ##cm^{-1}##. Is this based on the wave number ##k## for ##\Psi=Asin(kx-\phi)##? Thanks, KQ6UP

Homework Statement I took 2 spectra (measuring intensity) of a blank cuvette with a spectrometer. The first time (a) I did not put a black cloth on top of cuvette/spectrometer. The second time (b) I did put a black cloth on the system. The baseline of (b) was notably higher than the baseline of...

My name is Nicholas Lee, and I am studying neuroscience, and I am trying to find a way to find better ways in neuroimaging, and microscopy to see the brain better, to find better cure for Parkinson's disease, and Alzheimer's, and epilepsy If you have a four inch cubic block of glass, and carbon...

When you look at the emission/absorption spectrum of a single element, you can clearly see various emission/absorption lines, which are characteristic of that element. However, radiation from stars/galaxies contains spectra of many elements. How do astronomers make sense of this jumbled-up...

So the prof shows us how to tell if an object is red shifted, by comparing two spectra (i assume of the same object). The emission lines had similar gaps but were shifted right, therefore moving away from us. How can you obtain two different spectra of the same object if it's constantly moving...

I'm looking for reliable data of the spectra of different stars, anyone know any good resouces? Quantitative data would be best because I want to analyze it myself (not just find out something that was already on the site). Thanks in advance :)

Hi, everyone! I was thinking about atomic absorption/emission of photons and how they all have specific locations in the frequency zones as "lines" of missing/peak emissions. I'm curious if there is a scientifically proven/hypothesis of how the physical oscillation of atoms in molecules due to...

Hello Everybody, I'm looking into spectral analysis, and I couldn't find anything online about the spectra of different isotopes in discharge tubes (i.e. neon signs and the like ). Do different hydrogen isotopes have different spectra? If so, where could I find the data on the spectra? Thanks...

Hi pf. As I understand we know what a star is made of by looking at the absorption spectrum from a star. Since a star is a black-body it gives out a continuous spectrum of light but as this light passes through the Sun's atmosphere, certain wavelengths are absorbed depending on what the star is...

Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...

I was wondering how Rotational Spectra of diatomic molecule can be related to Heisenberg Uncertainty principle (Qualitatively). Being a QM model where rotational energies are quantized, there should be a qualitative reasoning on lines of the uncertainty principle, right? Anyone can direct me to...

Absorbtion spectra can be be observed by passing a WHite light ( light containing Wavelength from appx. 400nm to 700nm). Now here's My confusion! if We pass this Light from Hydrogen, It should not show dark lines in continuous band. ... (as to obsorb the Light of Visible region, It's electron...

I have done basic experiments where a laser is shot thru a grating and a lens is inserted at the diffraction pattern to put the spectra back together and form an image of the grating. apart from this being the single most mind blowing experiment ever to witness I have some questions about the...

PF, I work as a researcher at my undergraduate institution. I have to give a presentation in a week and this question always gets me. What does learning the properties of these SNRs contribute to the overall body of knowledge? What does the scientific community gain from this knowledge...

So i have a question regarding the nature of the particle spectre at alice as a function of momentum. The spectre in question can be seen here. http://cerncourier.com/cws/article/cern/48325. My question is, why is it that the particle in the low momentum range are rising and the reaching a...

Hello PF'ers, I am doing an unbinned likelihood analysis where I am analyzing the ratio of two spectra: \[ \frac{S_{1}(E)}{S_{2}(E)} = F(E) \] and each spectra, \[ S_{1}, S_{2} \] has its own data set. My first idea was to take the function, \[ F(E) \] and divide by the integral of...

Hello All, In this recent Navy publication, a team of researchers said they have discovered cusp confinement. This could be a major step towards fusion power. I am working on a write up of this publication. I am trying to understand their inferometry data. As far as I can tell, the...

Homework Statement Strong emission lines from calcium were observed at ##422.7nm##, ##610.3nm##, ##612.3nm##, ##616.3nm##, ##1034.9nm##, from transitions between ##4s^2##, ##4s5s## and ##4s4p##. The transition of ##422.7nm## was also observed at absorption. The singlet-triplet splitting of...

Homework Statement When reacted with a small quantity of water, SiCl4 produces an oxychloride X, SixClyOz. The mass spectrum of X shows peaks at mass numbers 133, 149, 247, 263 and 396. You should assume that the species responsible for all these peaks contain the 16O, 35Cl and 28Si isotopes...

In examining the IR spectrum, I noted that there were peaks for CH2-x where x is bromine, methylene (2 peaks) and a peak corresponding to a methyl group; I concluded that I've synthesized n-bromobutane. Is the method I used to interpret my spectra sound? *CDCl3 was the IR solvent In addition...

Hello, I am interested in computing the optimal depth of a copper absorber for Sr-90 decay electrons. I want to find a way to simulate a beta decay spectrum in C++. Have you got any idea or possible documentation on where I could start?? Thank you!

Hi Here is the number for the measured frequency for hydrogen 1s to 2s transition: 2 466 061 413 187 035 Hz By way of interest, what is our most accurate theoretical calculation of this number? I've tried the ordinary Bohr formula and it is only accurate to about 4 places. I'm also...

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...