[davidsha]

hi everyone,
i study to subject of atomic spectroscopy and i have difficulties understanding some principles.
1.what are the differences between emission and fluorescence? when i use each method?
2.when i measure emission, ain't i always measure fluorescence either?
3.atoms don't have vibrational nor rotational freedom degrees, so how come i saw on Harris book that there is a non radiative degradation at the electronic state?

[Corribus]

1.what are the differences between emission and fluorescence? when i use each method?

Usually used interchangeably. Technically, the latter is more specific, as there are many light emission mechanisms that are not fluorescence. In the broadest sense, "emission" doesn't even have to refer to light, so it's meaning has to be carefully inferred by context.

2.when i measure emission, ain't i always measure fluorescence either?

I don't understand the English.

3.atoms don't have vibrational nor rotational freedom degrees, so how come i saw on Harris book that there is a non radiative degradation at the electronic state?

Please elaborate. Atoms can still technically undergo nonradiative relaxation via photochemistry or energy transfer.

[davidsha]

thank you for your answers.
i will rephrase my second question..
i get the electrons to a higher level state, then i want to measure the emission/fluorescence.
how can i separate between the signals if they are both happening?

[kriggy]

Emmision is measured in the straight line from source-sample-detector while fluorescence is measured at angle - usualy 90°

[Corribus]

i get the electrons to a higher level state, then i want to measure the emission/fluorescence.
how can i separate between the signals if they are both happening?

How do you separate what signals? If you mean fluorescence from the incident radiation, you either take advantage of a combination of geometry, filters, or the Stokes shift (wavelength difference). If you mean emission from fluorescence, you don't - in most contexts they mean the same thing. Technically, emission can include some things that aren't fluorescence. E.g., a molecule can fluoresce and phosphoresce at the same time, and we'd refer to both of these as "light emission". You can distinguish these in a few easy ways, often just by inspection - what wavelength the signatures show up at. Phosphorescence is also often better observed at low temperature. The true way is to do time-resolved experiments, because the process rates are different.

If none of this is what you want to know, then you'll have to be more specific with the wording of your question.

[Enthalpy]

3. Atoms don't have vibrational nor rotational freedom degrees, so how come I saw on Harris book that there is a non radiative degradation at the electronic state?

During collisions among atoms maybe? Minimizing their effect is difficult.

At X-rays energy, more processes exist, for instance a higher electron can fill a lower vacancy, and an other electron be expelled, absorbing the energy difference. Though, I haven't heard of this in the visible spectrum.

[Irlanur]

During collisions among atoms maybe?

that's usually it.