If an atom absorbs an electron it must re radiate it but many times it is said that so along with absorption we must see emission lines but we see missing lines in abortion spectrum so where absorbed photon goes if it convert into heat energy how it take place
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1Possible duplicate of Why are there spectral lines at all? – John Rennie Aug 20 '17 at 05:30
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Related question by OP: https://physics.stackexchange.com/q/352652/2451 – Qmechanic Aug 20 '17 at 18:29
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If an atom absorbs a photon one of its electrons raises to an excited bound state (assuming, that the energy of the photon is insufficient for the atom be ionized). The relaxation occurs due to one of two processes:
- If the electron jumps to its original state, it emits the "same" photon (i.e the emitted photon has the same wavelength as the absorbed photon). However, it is very probable, that the direction in which the photon is emitted differs from the initial photon direction. Hence, the emitted photon does not reach the spectrum analyzer. Therefore, from the point of view of the analyses the photon is "lost".
- The electron falls into a different state of lower energy. Hence, it emits a photon of a different wavelength. Again it is improbable that the direction of the photon is equal to the initial direction. So this photon is probably "lost" as well.
So, it should not come as an surprise, that the emission lines of an atoms coincide with the absorption lines.
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