Spectra Definition and 285 Threads

The answer from answer key is electrons in gas absorb photon energy and causes electron to move to higher energy level. When electrons de-excite, photons emitted in all directions so dark lines occur. My question is if photons are emitted in all directions when electrons move from higher to...

I am now engaged in a study of real solids like Pu and Np. I need some knowledge of the X-ray photoemission spectra. Specifically, I need to understand the sudden approximation, the main and satellite peaks, etc. Is there any good reference on these topics? By the way, I do theory.

Hi Pfs I am reading this article: https://arxiv.org/abs/0810.2091 It is know that hearing the possible frequencies emitted by a drum are not enough to know its shape. Here the frequencies are the eigenvalues of the Dirac operator. the missing information is the unitary invariant of the title...

Basic stuff. Do emission and absorption spectra match? If so, why wouldn't hot stellar atmospheres exhibit both, cancelling? I'm a tourist...not physics minded..

Hello everyone, I have a small portable VIS-NIR spectrometer with a fiber cable connected to it to collect light and see the light spectrum on the screen. I have a question about the difference between collecting the so-called "unprocessed" intensity vs wavelength (counts vs lambda) spectrum...

Hello everybody! I have a silly question that is blowing my mind. When there is a circular polarized electric field, it can be interpreted as the real part of a complex field, for example $$E(t) = E_0( \hat{x}+i\hat{y}) e^{-i\omega t}$$ Now, for some selection rules it is useful to calculate the...

As suggested here http://svocats.cab.inta-csic.es/miles/index.php?action=search I tried downloading the VOTable, and FITS file (tried opening using Aladin and GIMP). However, when I open the file, I get a single line (I suppose the 2D spectra is contained in a single dimensional array?). Did I...

Hello! I have the spectra below measured, which shows transitions from a ##^{2}\Sigma_+## electronic level (the ground state) to an excited ##\Omega=3/2## level (there are several other level around it, so I decided that using Hund case c would be better, than Hund case a, but in Hund case a...

The definition of power spectrum of matter density field is given by eq(1). I have also seen definitions of power spectra given by eq(2) . Does this mean (2\pi^3) has been absorbed in the correlation function? $$P_{xx}(k)=(2\pi^3)\delta(k-k^\prime)<x(k)x(k^\prime)>$$ .. (1)...

Hi! I am doing some simple observations of different light sources with a simple DIY spectroscope. When I look at a computer screen I see what I believe to be an emission spectrum due to the dark spectrum with emission lines on it. Is this correct? And why does a computer screen emit an...

for undergraduate students how to explain this?

I'd like to compare 2 or more near-infrared spectra. The data consists of measured light intensity in different wavelengths (range 600 nm to 1100 nm). I'm wondering which statistical method would be appropriate? I noticed when searching online that pearson correlation might be inaccurate as...

Hi there, I am a physical oceanographer teaching an introductory undergraduate Earth science class that has a unit on astronomy. I have a physics undergraduate background, took a few astronomy classes at the undergraduate level back in the day, and did a bit of undergraduate research in...

According to this link you just have to anlayse the light that isn't coming from a place on the star that has a light the source directly behind it e.g wouldn't looking at light from the outer edge of star give you an emission spectrum? http://www.thestargarden.co.uk/Spectral-lines.html

What would be the best practices for comparing multiple NIRS spectra between each other? I’m working with NIRS data of multiple samples from different subjects, measured with the same measurement setup. The aim is in the end to analyse correlation between signals and anatomical differences...

In the context of Survey of Dark energy stage IV, I need to evaluate the error on a new observable called "O" which is equal to : \begin{equation} O=\left(\frac{C_{\ell, \mathrm{gal}, \mathrm{sp}}^{\prime}}{C_{\ell, \mathrm{gal}, \mathrm{ph}}^{\prime}}\right)=\left(\frac{b_{s p}}{b_{p...

Hello, I was wondering if someone could help clarifying this question. The question asks to estimate the energy state difference between the vibrational ground state of S0,v=0 and the first excited vibrational ground state S0,v=1 of the spectra below. The given solution: S1,v=1 -> S0,v=1 at...

I have the following equation, $$ C_\ell(z,z') = \int_0^\infty dkk^2 j_\ell(kz)j_\ell(kz')P(k),$$ where $$j_\ell$$ are the spherical Bessel functions. I would like to invert this relation and write P(k) as a function of C_l. I don't know if this is a well known result, but I couldn't find...

I was studying about atomic spectra of mono-electron species and in the pic it describes the ##4## series (principal, sharp, diffuse and fundamental). However I'm a little confused by the formula.Here my doubts are: Thanks for reading. [1]: [2]...

So tell me if I'm wrong, the left spectrum (white) and the right one (red) show spectra of two different galaxies (with different distances), right ? Why is it possible to know the velocity of the red-shifted spectrum by comparing it to the left one ??

Why do we see more absorption lines in stellar spectra than emission lines?

Hi, I really need your help. Suppose I have a Raman spectra of a hydroxyapatite, how do I calculate the bond length from the spectra? I've been trying to understand the concept of Badger's rule but I really cannot understand. Please help.

Hi I'm preparing some BCNO phosphor samples. Their basic structure is hexagonal Boron Nitride (h-BN) but it's doped with carbon and oxygen. The simplest BCNO phosphors are usually made from urea and boric acid alone, this already produces a BN structure with C and O impurities. I'm trying to...

I am trying to make a deconvolution of fluorescence spectra in Matlab. The original spectra is the yellow graph in the figure below. The other two graphs are Cauchy distributions, x and y, that I have manually added to the plot. I would like to write a program that could do this automatically...

My understanding of this is based upon the assumption that energy level transition is the only mechanism responsible for blackbody photons.

I understand that the intrinsic spin of an electron causes discrete differences in energy for transitions, due to the interaction of the magnetic dipole moment of the electron. Also, that this in turn creates the fine structure spectra. But what I am currently struggling to picture is why this...

In nuclear magnetic resonance, when should one process spectra in absorption mode and when - in magnitude mode? What is benefit of using the first one and the second one? For example, I need to integrate spectrum. In this case, what should I use - absorption or magnitude mode?

Hello guys (and girls), I'm trying to determine the dark phase of a type Ia supernovae. In order to do that I need to calculate the photosphere's velocity. So I'm trying to determine the redshift of the Si II in the spectra, by finding the minima in the absorption line. But what kind of...

In any quantum system, the differences of the energy levels (the eigenvalues of the Hamiltonian ##H##) are in principle directly observable, since they represent excitable oscillation frequencies of the system and thus can be probed by coupling the system to a harmonic oscillator with adjustable...

So I was taught in school that heated low density gases produce spectral lines and cool low density gases absorb their spectral lines. I mentioned this to my husband and he asked me what the definition of hot and cool were and I had no idea. The more I thought about it, the more confused I...

as homework, I have to do the following exercise: Bremstrahlung emission : We are interested in ionized plasma of density ##n##, at temperature ##T## with ions of charge number ##Z##. 1. Explain the physical origin of bremstrahlung radiation 2. Represent the expected spectra (shape and...

It doesn't make sense to me that absorption spectra are (mostly) continuous. Here are my beliefs. Please tell me which piece/pieces is a/are misconception(s). 1) When light is absorbed, the energy is used to excite an electron to some discrete energy level. 2) To get to this discrete energy...

I am trying to plot the absorption curve of a given sample using some spectrophotometric data. The data that I've collected are transmittance ##T## and reflectance ##R## – the ratios of transmitted and reflected light power to incident light power. However, using two different methods I got two...

I've been doing some spectrum extractions in IRAF, stellar and galactic, and I was wondering if anyone here had any ideas on how to tell if the extraction/calibration/etc went well? I have a bunch of finished projects but I'm not sure about how to tell if they're any good or not. Let me know if...

Hi! I'm trying to understand a perfectly black body. So the definition I have found is that a black body is one that absorbs radiation of ALL wavelengths and reflects NONE. Therefore it appears black at low temperatures. And when heated it emits radiation of all wavelengths making it appear...

My question is regarding absorption and emission lines. As far as I understand, when a photon of the "right" wavelength passes through an atom, an electron is excited and takes on a higher energy state, in proportion to the energy imparted by the photon. This is the "absorption" part. However...

Hello, I was wondering if anyone here had experience using the dataset of the Sloan Digital Sky Survey, i want to exract quasar's spectra (precise quasars of which I have the reference). Thanks

why pure rotational spectrum is almost always seen as absorption lines,and not as emission lines?

Hello, A low density gas, when heated at a temperature T, emits radiation having a line spectrum, i.e. having only discrete spectral lines. Each spectral line corresponds to a very specific energy transition (jump) for the electron in the atom. Some energy transitions are allowed, some are...

Hi, why do unbounded operators and bounded operators differ so much in terms of defining their spectra? 1. The unbounded operator requires a self-adjoint extension to define its spectrum. 2. A bounded one does not require a self-adjoint extension to define the spectral properties. 3. Still the...

Homework Statement [/B] The top spectrum shows part of the Sun's spectrum. State and explain which letter best represents the light from a star that is similar to the Sun. Homework Equations None. The Attempt at a Solution I originally was thinking A but my book says B but only gives...

I'm reading about star spectra, color, and temperature and have a question... I understand that very hot stars burn blue because a lot of the radiation is on the UV end so it appears more blue when its ran through several color filters. and the opposite applies for cool stars that are skewed...

Hello every one I deposited TiO2 thin layers on glass conductive substrate and then i took there absorption spectra. My question is why do i see interference fringes in the absorption spectra of my samples.

Is there a way to look at mass spectra and determine the method of ionization? I.e., whether it's electrospray, FAB, MALDI, etc.

The selection rule for rotational spectra ##ΔJ = ±1##. Is it always true for the emission part of rotation spectra ##ΔJ = -1## and how?

Hi all, I'm wondering how, for each peak in an x-ray spectra from a material (and using a crystal analyser), it is determined which energy level jump the peak corresponds to? How would you figure out the correct value of n to substitute into Bragg's Law to find the energy of the beam? Thank you!

Hi guys, Im new here so I am going to get right to it. Excuse my grammer I am on my mobile. So I am trying to understand the difference in absorbance spectra of NAD+ and NADH. I have seen this touched on on this site but not directly answered. NAD+, with an apparent two aromatic structures...

How hot does a gas have to be to achieve its emission spectrum with a glass prism?

In thermal imager vs IR spectroscopy, they both look at the IR radiation of an object. What is the difference between the two.. I know IR spectroscopy look at the dipole moments of molecules. But in thermal imager.. do they also image the dipole moments of molecules? Also why you see images in...