# Tag Info

3

The linewidths come out very naturally from Maxwell's Equations by treating the atom as a tiny classical antenna. I do the calculations for the 2p-1s transition in hydrogen on my blogsite here: The Semi-Classical Calculation The idea is that from the Schroedinger equation, the superposition of the s and p states gives you get a tiny oscillating dipole about ...

6

The answer is yes, the atom does absorb radiation that does not exactly match the transistion frequency. This is due to the Doppler effect that everyone knows from an ambulance with siren driving by. The frequency you hear is higher if the ambulance moves towards you and lower if it drives away from you. It's the same with the atom. If the atom moves (and ...

6

According to Bohr model, the absorption and emission lines should be infinitely narrow, because there is only one discrete value for the energy. There are few mechanism on broadening the line width - natural line width, Lorentz pressure broadening, Doppler broadening, Stark and Zeeman broadening etc. Only the first one isn't described in Bohr theory - it's ...

1

since every sample has both protons and electrons, and all have magnetic spin, But the electron spins cancel out usually, because normal matter only has electrons in Pauli pairs. EPR is restricted to radicals in organic chemistry or transition metal complexes, or O2 gas :=)

2

Spectroscopy: you pass the light through (or reflect from) a dispersive element (a prism or diffraction grating) and then you record the dispersed light. You have a record of the intensity of the light as a function of wavelength. Advantage: potentially you can record the light of one or more objects over a very wide wavelength range and have excellent fine ...

1

You are correct that time and frequency domains are just Fourier transforms of each other. However you only have full information if you have amplitude and phase information (as opposed to a power spectral density which is only amplitude information in the frequency domain). Frequency spectra might tell you that you have multiple modes that exist, but it ...

2

Fluorescence is mostly red-shifted with respect to the excitation wavelength, as part of the energy goes to excite molecular vibrations. However, the reverse process also happens: if a molecule was vibrationally excited before electronic excitation, it can contribute this energy to fluorescence, which in this case is blue-shifted (so-called hot bands). The ...

1

The normal nonresonant Raman scattering happens when a photon interacts with a molecule; the molecule absorbs the photon momentarily and re-emits it with slightly less energy. In an energy diagram, that looks like this. The frequency of the incoming photon is $\omega_i$, and the frequency of the scattered photon is $\omega_s$. The thick lined level is ...

1

I was unable to see any Fraunhofer lines with the sun light, despite using a focusing lens. However, I tried examining the light of a fluorescent bulb instead. I didn't manage to project the image on a sheet of paper, but I was able to take a direct picture of the image in the prism. The result is a bit more satisfying: / Are these four lines a ...

14

The resolving power of a prism is given by the formula $$\frac{\lambda}{\Delta \lambda} = b\ \frac{dn}{d\lambda},$$ where $b$ is the base length of the prism, $\lambda$ is the wavelength and $n(\lambda)$ is the refractive index. You don't say, but let's assume you are using a crown glass prism. According to this useful document, crown class has ...

3

The sodium line that is being referred to is a reasonably sharp, dark absorption feature that is seen in the orange part of the visible spectrum of the bulk of stars that make up the light from a distant galaxy. The absorption is caused because stars are hotter in the middle than they are on the outside. The relatively cool gas on the outside has sodium ...

1

It is a standard line in the atomic spectrum of sodium, that is used as a standard The line you refer to in nmeters is a standard line because of its strength for determining refractive indices of materials in the lab. A reference wavelength of 589.3 nm (the sodium D line) is most often used. T The evolution of the line due to the motion of the ...

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The emission spectrum of sodium contains two very bright yellow lines called the D lines. Since they are so bright and so easily seen they are something of a favourite for spectroscopic studies. In this case the question is referring to the D1 line, which has a wavelength of 588.9950nm (the D2 line at 589.5924nm is only half as bright as the D1 line). The ...

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Spectroscopy is used on solids to determine some of its properties, but it can be used on gas as well. The experiment (for UV light, using H, He, Ne and Ar) was done in 1941 by Takamine and Tanaka, and written up in Astrophysical Journal, vol. 93, p.386 (DOI 10.1086/144275). You can find the write up at this link Quoting just a short section: ...

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