What is Spectral lines: Definition and 54 Discussions

A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected "fingerprints" of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible.

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  1. Z

    Comparing spectral lines between 2 stars to calculate the difference in temperature

    TL;DR Summary: A weak spectral line connecting levels in neutral iron has been observed for a number of solar-type stars. Its lower level has an excitation energy of 2 eV. If the line’s equivalent width is twice as large for star A as for star B, how great is the difference in temperature (in...
  2. starryexplorer

    I Obtaining Transit Spectrum for Celestial Bodies Using JWST NIRSPEC

    I've recently been tasked with obtaining transit spectrum data for some fascinating celestial bodies, including Ceres, Enceladus, Ganymede, Io, and Titan. The goal is to compare their transit spectra with that of Earth. However, I'm facing a bit of a challenge when it comes to using the Github...
  3. Pushoam

    Spectral lines in the emission spectrum for an electron at n= 3

    Since there is only one excited electron, it could come from n=3 to n =1directly or n=3 to n =2 and then n=2 to =1. Hence, there could be one or two lines depending upon the path taken by electron. Is this right?
  4. Yuras

    B Spectral lines and superposition of states

    Let's say atom has two energy levels, ##E_1## and ##E_2##. If atom is in the first state ##|E_1\rangle##, then it's able to absorb a photon with energy ##E_2-E_1##, while transitioning to the second state ##|E_2\rangle##. In atom's spectrum we can see an absorption line at the corresponding...
  5. O

    I Why are the spectral lines weak in my hydrogen Geissler tube?

    Using a hand spectroscope, I looked at the spectrum of two geissler tubes, helium and hydrogen. The helium spectrum is what I expected, dominated by five distinct lines. The hydrogen spectrum, however, is somewhat disappointing. It is dominated by an almost continuous spectrum, it is not evident...
  6. D

    I Find the interference function for different emission modes

    Homework Statement:: Find the interference function ##I(\delta)## where The emission is analyze by a Michelson interferometer. Relevant Equations:: ##I(\delta) = \frac{1}{2} \int_{-\infty}^{\infty} G(k) r^{ik \delta} dk## ##I(\vec{r}) = I_1 + I_i + 2 \sqrt(I_1 I_i) cos (k\delta)## I have 5...
  7. A

    How much does the equivalent width of a line change by the introduction of 5% scattered light?

    How much does the equivalent width of a line change by the introduction of 5% scattered light? We know the equivalent width is defined as We know the equivalent width is defined as $$W = \int_{-\infty}^{\infty} \bigg(\frac{1-F_{\nu}}{F_c}\bigg) \, d\nu$$ where ##F_{\nu}## represents the flux in...
  8. R

    B Spectral Lines: Scrambling & Differentiation

    How are different elements spectral lines naturally 'scrambled' and then differentiated by observation, into each and every element contained in a 'single' light beam emanating from a light source? Is the term 'single' correct in this context and if not can you explain why?
  9. B

    B How Can a Hydrogen Atom Emit Multiple Colors Simultaneously?

    If the spectral line of Hydrogen contains four colors, I don’t understand how the electron can jump four times to four different energy levels in the same moment?
  10. John Greger

    How Do You Identify Spectral Lines and Calculate Fine Structure Constants?

    Homework Statement The Ca spectrum below, recorded using a Fourier Transform Spectrometer (FTS), shows the resolved ##3d4s ^3D - 3d4p ^3D## multiplet. The wavenumbers and their relative intensities are given in the table. Identify all the lines and determine the fine structure constants in the...
  11. Andrew Church

    I Composition of the Sun: How We Know via Spectral Absorption Lines

    The question “how do we know the composition of the sun” falls shorts everywhere I look. 1. There is the spectral absorption lines. Explanations given how that works, indicate how we know the elements, but fails to tell us how we know about the preponderance of Hydrogen and Helium...
  12. P

    Interferometer- 2 spectral lines

    Homework Statement An interferometer is illuminated by light from a sodium lamp, which emits two narrow spectral lines at wavelengths of 589.0nm and 589.6nm, with the intensity of the 589.0nm line being twice that of the 589.6nm line. Show that there are values of d at which the visibility of...
  13. A

    I Rotational Spectra: ΔJ Selection Rule & Emission Part

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

    Calculation of no. of spectral lines for group of similar atoms

    Homework Statement The maximum no of spectral lines for a single atom during it's electron's transition is given by [∆n(∆n+1)]/2 . But I don't seem to arrive at the answer when a group of atoms are present . The question was - What is the maximum number of spectral lines possible for Balmer...
  15. P

    B Definition of unshifted spectral lines?

    Hi, N00b question :-) I have read articles about redshift and blueshift and have a good idea about them. What I would like to know is how you decide if something is "unshifted" - what is the definition of this? is there a standardized way of defining/mapping an element's unshifted spectral...
  16. J

    I How can I identify the appropriate spectral line for Doppler calculation?

    Hi, I was looking into Doppler shift calculations, and I came across this blog post. It gives a very simple and straight forward account of calculating the velocity of a star. Following is the summary the blog post: Spectrum of Alpha Centauri (A. Cen.) is obtained through Lhires III...
  17. Domenico94

    Continuous and discrete spectra

    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?
  18. victorhugo

    I Hyperfine splitting and relative intensity of spectral lines

    What is the cause of hyperfine line splitting? I saw somewhere that it was because of spin quantum number and somewhere else that it was because of how electrons interact in the atom. And relative intensity of spectral lines? I'd assume it's due to the probability of electron jumps being more...
  19. N

    Hydrogen, Deuterium, and Tritium Ionization Spectra

    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...
  20. G

    Xenon Spectral Lines: Exploring the Mystery

    spectral lines As far as I understand spectral lines represent allowed transitions between energy levels in a particular atom. And that the number of energy levels should increase with increase of a number of electrons, due to electron-electron and spin-angular-momentum couplings. Right...
  21. R

    Measuring redshift from type 1a supernova

    I know that you can measure redshift from stars by looking at the shift in there balmer lines or more generally there line absorption spectra and seeing how far these lines have shifted from actual balmer lines or line absorption spectra of the same elements on earth. But how would you...
  22. N

    Understanding Spectral Line Width and Causes | Optical Wavelengths

    Hi! I have two questions regarding spectral lines, in the optical wavelengths. Every line has a width. One reason is the uncertinity in energy of the atomic states according to Heisenberg uncertinity relation. But this is just a very small part of the width, I think. Are there other causes to...
  23. 2

    Question about spectral lines of stars?

    I can't seem to find an answer to this quick question: which part of the star causes the observed spectral lines? As I understand, the photosphere is the deepest visible layer of the star, and then light passes through the chromosphere and the corona. I would think that both the chromosphere and...
  24. G

    Why do we see spectral LINES, not circles/triangles etc?

    We were looking at the spectral lines of sodium in class and I was wondering, why do we see lines, and not any other shape like circles?
  25. neilparker62

    New Formula for Hydrogen Spectral Lines Wavelengths/Frequencies

    Hi I have a new formula (or at least I think it's new) for predicting the wavelengths/frequencies of hydrogen's spectral lines. Please take a look and tell me if it is new. I am quite confident that it works because Bohr's original formula 'falls out' if one approximates cos(x) as 1 + x^2/2...
  26. P

    Spectral lines and energy levels

    Homework Statement In the spectrum depicted bellow (see added picture) are spectral lines which resulted from emissions of a photon due to an electron decaying from a higher to a lower orbital in a Hydrogen-like atom (meaning- only one electron. No details about the nucleus) All lines in the...
  27. Absentee

    Sommerfeld model and fine spectral lines

    Hey guys! First time posting on this site. Been reading for quite a while and really loving it! :thumbs:! I'm a chemistry student and reading my book in general chemistry I couldn't understand two things about Sommersfeld's atomic model. I believe i understand the whole concept but what...
  28. E

    Observing Spectral Lines: The Highest Order & Color Sequence

    Homework Statement In a question I was asked, assuming a spectrometer reading of Hydrogen produced two strong spectral lines at 656.3nm and 410.1nm. And also assuming the diffraction grating had 500 lines/mm What is the highest order of spectrum which can be fully observed , i.e value of m...
  29. Einj

    Find atomic number from spectral lines

    Homework Statement An atom or ion with one electron has energy levels E_n=-A/n^2. Tw neighboring lines in its spectrum at room temperature have wavelengths \lambda_1=97.5 nm and \lambda_2=102.8 nm. (Note that hc=1.240\times 10^{-6} eV m). (a)What is the constant A? (b) Identify the atom...
  30. G

    Spectral lines from multiple atoms

    Homework Statement "A gas discharge tube contains H 1 , H2, He 3 , He4, Li6, and Li7 ions and atoms (the superscript is the atomic mass), with the last four ionized so as to have only one electron. (a) As the potential across the tube is raised from zero, which spectral line should appear...
  31. H

    Spectral Line Question: True or False?

    This lady who takes our class, she set this question in one of our papers: 'The wavelengths of the dark lines are exactly the same as those of bright lines in the absorption spectrum.' - True or false? I answered true. Have I been wrong?
  32. P

    Hydrogen Atoms and Spectral Lines

    We know that hydrogen atom has got one electron.But If we look a hydrogen spectrum there are lots of spectral line. How can that be possible? Because in Bohr's atomic model the spectral lınes mean, electrons energy levels.It shows there is possible energy levels which electrons can...
  33. S

    Spectral lines and absorption lines

    On PF, to answer why atmosphere is transparent, users explained that atmospheric gases such as oxygen do not have absorption lines in the visible spectrum. On UColorado website, under Spectral Lines, they show that Oxygen has many visible lines in its spectral signature. This confuses me...
  34. E

    Width of Spectral Lines: Explaining Main Sequence Star Determination

    It's given in my book that from the width of spectral lines you can determine whether or not it is a main sequence star... Not sure if astro-como or quantum.. Anyway, i need a detailed easy explanation of what is the width of spectral lines.. Secondly, if we know that how will we determine...
  35. B

    Excited electrons and spectral lines

    Homework Statement Well,the problem is such : There are two hydrogen atoms.In each atom electrons were excited to the same energy level.Lifetime of one of the excited electrons is t1,when lifetime of other is t2. The question is : Which on of them had more wider spectral line,when during...
  36. E

    Exploring the Last Four Jumps in Hydrogen's Spectral Lines

    When a completely ionized atom of hydrogen captures an electron, the latter may conceivably cascade toward the nucleus by jumping successively from one permitted orbit to the next. If we could watch the light emitted by this single atom, to what lines of the complete hydrogen spectrum will the...
  37. V

    What Energy Levels Create the Spectral Lines of Element Fb?

    Homework Statement A meteorite found in Antarctica contains a trace of a mysterious element. Its spectral lines are all multiples of a frequency f0. The multiples are: 1, 2, 3, 5, 6, 8, 10, 11, 13, 16, 18, 19, 21, 26, 29, 31, 32, 34, 42, 47, 50, 52, 53 . The frequencies in bold have...
  38. T

    What methods are used to CONFIRM the compisition of a star from spectral lines?

    So I know that we can use absorption or emission lines from a star or object emitting light to determine the composition of that object. But what methods are used to confirm that? We've been doing this in class and it seems rather primitive to eyeball the lines and compare them with example...
  39. O

    Emission Spectral Lines & the Rydberg Formula

    FIGURED IT OUT, PLEASE DISREGARD Homework Statement Find the shortest wavelength of the Lyman series for a triply-ionized beryllium atom (Be3+). Express your answer in nanometers using four significant digits. Homework Equations Rydberg's Formula: 1/\lambda=RZ2(1/n12 - 1/n22) The Attempt...
  40. R

    Electron Transitions and Spectral Lines Conceptual Question

    Homework Statement The spectrum of a hypothetical atom is shown in the figure. Three distinct spectral series are shown, with the center series corresponding to transitions to a final state of n_f = 3. (f is final) The indicated spectral line corresponds to the transition from an initial state...
  41. F

    Black body radiation verses spectral lines.

    When objects are heated they produce blackbody radiation which varies with their temperature, and when the electrons in the orbitals of atoms are given energy they produce radiation at specific frequencies known as spectral lines. My question is this. When an object, say a piece of mental is...
  42. K

    Why Does Hydrogen Emit a Line Spectrum Instead of a Continuous Spectrum?

    Homework Statement My Chemistry book says: "Before reading further about the details of Bohr's model, speculate as to how they explain the fact that hydrogen gas emits a line spectrum rather than a continuous spectrum." Homework Equations The Rydberg Equation, though I suppose this is more...
  43. M

    How does the spectral lines of Hydrogen occur?

    I'm not sure but I found this... [When an electron makes a transition from one energy level to another, the electron emits a photon with a particular energy. These photons are then observed as emission lines using a spectroscope. The Lyman series involves transitions to the lowest or ground...
  44. S

    Why do spectral lines only appear as a line?

    i'm a newbie to quantum theory so bear with me please :) when hydrogen is heated in a vaccuum, the electron gets excited and moves to a higher energy level right? and then emits light as a spectral line when it moves back down to the lower energy level. my question is, why does it only show up...
  45. S

    Find angular seperation of spectral lines with a grating spectrometer

    Homework Statement find the angular separation between the red hydrogen-alpha spectral line at 656nm and the yellow sodium line at 589nm if the two are observed in third order with a 3500-line/cm grating spectrometer. Homework Equations maximum equation for multi-slit interference d...
  46. N

    Please, will you explain the nature of spectral lines

    Hi, I was wondering what really ARE spectral lines? Are they electromagnetic waves? But still they are affected by magnetic & electric field in the Zeeman and Starks effect respectively, whereas the electromagnetic waves are not. so is there any theory explaining...
  47. Amith2006

    Fine structure of spectral lines

    While going through some concepts in spectroscopy, i got stuck in fine structure lines. So, i need some clarifications in this topic. Now, it is known fact that fine structure lines can be explained by the concept of electron spin. Aren't these lines as a result of spin orbit interaction? Apart...
  48. L

    Why Do Different Elements Have Unique Spectral Lines?

    why do different spectral lines appear for the excitation of different elements? I know that electrons jump to lower energy levels gives off photons of distinct frequencies but why characterizes them to be a certain frequency for each element? why doesn't an electron in a high orbital (say n=2)...