Question

I'm doing Raman Spectroscopy in Physical Chemistry lab.

What physically is occurring to the solvated acetone molecules to cause the frequencies to shift?

Answer 1

Transition Dipole Moments

The transition dipole moment is regarded as a measure of charge redistribution that accompanies a transition. The intensity of a transition is directly proportional to the square of the transition dipole moment. This can be derived from the time-dependent perturbation theory, which states that for a molecule to interact with an electromagnetic field and absorb or emit a photon with a given frequency, it must possess a dipole oscillating at that same frequency. Spectroscopic transition rules can also be derived from the transition dipole moment, where a forbidden transition has a zero dipole moment, but an allowed transition has a non-zero dipole. The value and magnitude of the transition dipole moment are reflective of the strength with which a given molecule or complex couples with the electromagnetic field. Solvatochromic shifts are an indication of a large shift in electron density as a result of the transition, thus consistent with a large transition dipole moment

Charge Transfer Bands

Charge transfer (CT) bands exist in metal complexes when electrons flow between orbitals that are predominantly metal in character and orbitals that are predominantly ligand in character. Charge transfer transitions are often identified by their high intensities. If the electron migration is from the metal to the ligand, the transition is classified as a metal-to-ligand charge transfer (MLCT). Often, metals in low oxidation states with ligands having low-energy acceptor orbitals, such as those capable of ?-backbonding, exhibit MLCT bands, for example tris(2,2

Answer 2

physically is occurring to the solvated acetone molecules to cause the frequencies to shift

The transition dipole moment is regarded as a measure of charge redistribution that accompanies a transition. The intensity of a transition is directly proportional to the square of the transition dipole moment. This can be derived from the time-dependent perturbation theory, which states that for a molecule to interact with an electromagnetic field and absorb or emit a photon with a given frequency, it must possess a dipole oscillating at that same frequency. Spectroscopic transition rules can also be derived from the transition dipole moment, where a forbidden transition has a zero dipole moment, but an allowed transition has a non-zero dipole. The value and magnitude of the transition dipole moment are reflective of the strength with which a given molecule or complex couples with the electromagnetic field. Solvatochromic shifts are an indication of a large shift in electron density as a result of the transition, thus consistent with a large transition dipole moment

We studied solvated structures of jet-cooled pyrrole