Energy transitions are classified according to spectral series such as Balmer, Lyman, Paschen, etc., which assume a single transition between two non-contiguous levels (except the first transition). What the question really means is, can cascading transitions from one level to another, emitting a photon at each contiguous level, occur or have been observed?
Yes, cascading transitions can be observed provided you have the option to detect the corresponding spectral region by a spectrograph. For example, if you excite the hydrogen atoms by a VUV source of radiation corresponding to a transition from n=1 to n=4, you will observe the fluorescence at 656 nm as well as 486 nm the member of the Balmer series in addition to the first member of the Pickering series (from n=4 to n=3 transition) that will be in the infra red region. Similarly, we have detected the cascading transition in sodium atomic spectra.
I hope my answer will be of any to you. If you need further help, please respond.
Muhammad: Thanks for your answer. I suspected that was the case, although the literature seems to focus on the transition series. Your answer leads to a few secondary questions. Do cascade transitions occur in all cases of excitation, but not always observed? Or do they occur under some circumstances and not others? If the latter, do we know why? I am doing investigative research on subatomic energy exchanges and your answers would be most helpful. Thank you.
Dear Bernardo,
The cascade transitions are are always present and they occur in accordance with the dipole selection rules. The simple example is the fluorescence spectrum or the Laser produced lithium plasma spectrum that we published last year in Physics of plasma. As I said earlier, one has to look in the corresponding wavelength region where the cascade transition occurs.I can send you the spectra of lithium and aluminum, both have been published in Phys. of Plasma in 2011.
best wishes,
Aslam
Dear Muhammad,
Thanks for your prompt and very helpful answer. I took this long to thank you because, since your answer had satisfied my inquiry, I was looking into closing the thread. I was informed by the Community Support Service at RG, that it is not possible to close a Q&A thread and was given some kind of reasonable justification for it. I'm glad I took this long because while searching the Internet further on the cascade transitions subject, I found a couple of places that mentioned that transitions from the first excited state of hydrogen to its ground state take about 10^-8 seconds. It is fascinating to me how a seemingly spontaneous event can take a repeatable amount of time. So if I may impose on your amiability once more, is this relaxation period a calculated value or an observed one? I would also appreciate if you can point me to any place that can inform me on the subject of hydrogen transition relaxation times as a treatise, if there is one, I tried for many hours searching the Internet to find more information on the subject to no avail. In any case, my thanks again. Bernardo.
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