why we always get band spectra instead of line spectra ?
Answers
Explanation:
Line spectrum(also called atomic spectrum) is produced when when atom of a particular element is irradiated with energy* ,causing excitation of outer shell electron(s) to higher state. When these electron(s) return to their ground state , they emit their excitation energies corresponding to a particular frequency(and hence a particular wavelength, for the medium). This in spectroscopy shows as line.(characteristic of an element)
However, if a Molecule(may be of same or different element) is irradiated, apart from the exitation- there will be additionally rotational or vibrational movements taking place(as is permitted by the degrees of freedom). This is what accounts to the several line spectrum combined as a Band Spectrum.
{Also to note here is that in case of heteroatomic molecule, there will be diffrent line spectrum characteristic of diffrent elements}.
| Note: An atom has a unique stable electronic cloud configuration known as ground state, the most distant electronic cloud being very loosely bound due to less binding energy|
*the energy input required should be minimally enough to make the electron in most distant cloud(or in outermost valence orbit) free of the Coulombic forces of Nucleus