Spectre de l'atome d'hydrogène

Résumé

Le spectre de l'hydrogène est l'ensemble des longueurs d'onde présentes dans la lumière que l'atome d'hydrogène est capable d'émettre. Ce spectre d'émission est composé de longueurs d'onde discrètes dont les valeurs sont données par la formule de Rydberg : : \frac{1}{\lambda} = R_{\mathrm{H}} \left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right) où :

\lambda est la longueur d'onde de la lumière dans le vide ;
R_{\mathrm{H}} est la constante de Rydberg de l'hydrogène ;
n_1 et n_2 sont des entiers tels que n_1 < n_2.

Interprétation L'hydrogène est le premier atome de la classification périodique. Il est formé d'un proton et d'un électron. L'énergie de l'électron dans le référentiel barycentrique ne peut prendre que quelques valeurs discrètes, appelées niveaux d'énergie (voir modèle de Bohr puis orbitale atomique). Lorsque l'électron passe d'un niveau élevé à un niveau plus bas, il émet un photon do

Source officielle

https://fr.wikipedia.org/wiki/Spectre_de_l'atome_d'hydrog%C3%A8ne

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IOP Science2019

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Carbon K-edge x-ray emission spectroscopy of gas phase ethylenic molecules

Camila Bacellar Cases Da Silveira, Thomas Roland Barillot, Majed Chergui, Rebecca Ann Ingle, Luca Longetti

We report on the C K-edge x-ray absorption spectra and the resonant (RXES) and non-resonant (NXES) x-ray emission spectra of ethylene, allene and butadiene in the gas phase. The RXES and NXES show clear differences for the different molecules. Overall both types of spectra are more structured for ethylene and allene, than for butadiene. Using density functional theory-restricted open shell configuration interaction single calculations, we simulate the spectra with remarkable agreement with the experiment. We identify the spectral features as being due to transitions involving localised 1s orbitals. For allene, there are distinct spectral bands that reflect transitions predominantly from either the central or terminal carbon atoms. These results are discussed in the context of ultrafast x-ray studies aimed at detecting the passage through conical intersections in polyatomic molecules.

IOP Publishing Ltd2022

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Because the spectral d. of Rydberg states scales with the third power of the principal quantum no. n, the region immediately below at. and mol. ionization thresholds is spectrally very dense. Studying the properties of high at. and mol. Rydberg states just below threshold (at n>100) thus represents a real exptl. challenge. At the same time, it offers the opportunity to obtain, by Rydberg series extrapolation, very detailed information on the energy level structure of mol. ions. Recent exptl. progress will be reviewed that have enabled us to obtain information on high at. and mol. Rydberg states at an unprecedented resoln. The methods we have developed rely on the use of a home-built broadly tunable near-Fourier-transform-limited pulsed extreme UV laser system with a bandwidth of better than 210 MHz and of double-resonance techniques with which the spectra of high Rydberg states can be measured at a spectral resoln. of 60 kHz. Recent applications of these methods to the study of the threshold ionization of small mol. systems will be presented. [on SciFinder (R)]

2001

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