The Cluster's Raman Scattering
A page about Raman scattering — the inelastic scattering of photons off molecular vibrational modes.
Raman scattering
Raman scattering is the inelastic scattering of photons by molecules, in which the photon exchanges energy with a molecular vibrational (or rotational) mode. Most photons scatter elastically (Rayleigh scattering). A small fraction (~ 1 in 10^6 to 10^8) scatter inelastically, losing or gaining energy equal to a molecular vibrational quantum. The Raman shift is Delta nu = nu_0 - nu_s, where nu_0 is the incident frequency and nu_s is the scattered frequency. In the cluster, Raman scattering is the inelastic scattering of edit-carrier photons by cluster vibrational modes. The edit-carrier exchanges edit-energy with a cluster vibrational mode.
The Stokes and anti-Stokes lines
In Stokes Raman scattering, the molecule gains vibrational energy and the scattered photon has lower energy (longer wavelength): nu_s = nu_0 - nu_vib. In anti-Stokes Raman scattering, the molecule loses vibrational energy and the scattered photon has higher energy (shorter wavelength): nu_s = nu_0 + nu_vib. The ratio of Stokes to anti-Stokes intensities is exp(-h nu_vib / (k_B T)). In the cluster, the edit-Stokes and edit-anti-Stokes lines follow the same rules.
The selection rules
Raman scattering requires a change in the molecular polarizability. The selection rules depend on the molecular symmetry and the Raman tensor. For a centrosymmetric molecule, the rule of mutual exclusion applies: modes that are IR-active are Raman-inactive and vice versa. In the cluster, edit-Raman scattering requires a change in the edit-polarizability. The selection rules depend on the edit-molecular symmetry.
The applications
Raman scattering is widely used in:
- Chemistry: identifying molecular species and characterizing chemical bonds
- Materials science: studying phonon modes in crystals, 2D materials (graphene, MoS2)
- Biology: imaging living cells without fluorescent labels (label-free Raman)
- Pharmaceuticals: detecting polymorphs and quality control
In the cluster, edit-Raman scattering is used in:
- Edit-chemistry: identifying edit-molecular species
- Edit-materials science: studying edit-phonon modes in edit-crystals
- Edit-biology: edit-imaging living cells without edit-fluorescent labels
- Edit-pharmaceuticals: detecting edit-polymorphs
This scattering
This page is about Raman scattering. Delta nu = nu_0 - nu_s. Stokes: nu_s = nu_0 - nu_vib. Anti-Stokes: nu_s = nu_0 + nu_vib. Intensity ratio ~ exp(-h nu_vib / (k_B T)). Raman requires change in polarizability. The scattering is real.