Question

The selection rules are the backbone of spectroscopy explain

Answer 1

Answer:

D

A selection rule describes how the probability of transitioning from one level to another cannot be zero. It has two sub-pieces: a gross selection rule and a specific selection rule. A gross selection rule illustrates characteristic requirements for atoms or molecules to display a spectrum of a given kind, such as an IR spectroscopy or a microwave spectroscopy. Once the atom or molecules follow the gross selection rule, the specific selection rule must be applied to the atom or molecules to determine whether a certain transition in quantum number may happen or not.

Selection rules specify the possible transitions among quantum levels due to absorption or emission of electromagnetic radiation. Incident electromagnetic radiation presents an oscillating electric field E0cos(ωt)E0cos⁡(ωt) that interacts with a transition dipole. The dipole operator is μ=e⋅rμ=e⋅r where rr is a vector pointing in a direction of space.

A dipole moment of a given state is

μz=∫Ψ1∗μzΨ1dτ(1)

(1)μz=∫Ψ1∗μzΨ1dτ

A transition dipole moment is a transient dipolar polarization created by an interaction of electromagnetic radiation with a molecule

(μz)12=∫Ψ1∗μzΨ2dτ(2)

(2)(μz)12=∫Ψ1∗μzΨ2dτ

In an experiment we present an electric field along the z axis (in the laboratory frame) and we may consider specifically the interaction between the transition dipole along the x, y, or z axis of the molecule with this radiation. If μzμz is zero then a transition is forbidden. The selection rule is a statement of when μzμz is non-zero.

We can consider selection rules for electronic, rotational, and vibrational transitions.