Definitions Flashcards
Describe Raman scattering.
We can see transitions between all the vibrational (and irrotational) modes in the infrared light through Raman spectroscopy. The sample is illuminated at IR light and the molecules transition between levels by absorbing one of these photons and emitting another photon of a different frequency.
Describe stokes and anti-stokes in Raman spectroscopy.
If the difference in energy between the final and initial photons are negative we get Stokes scattering and if positive we get anti-Stokes scattering
Describe X-ray spectroscopy.
We use an X-ray tube to accelerate electrons at a target of interest. Some accelerated electrons collide with the atoms of the target and eject an electron from one of their inner orbits. This leaves a hole. An electron from a higher orbital will jump down to fill this vacant spot emitting an X-ray.
Describe the Relativistic correction.
In the ground state of the hydrogen atom, the electron moves with speeds of approximately 0.01c. This is sufficiently fast that we need to correct for special relativistic effects.
Describe the spin orbit coupling correction.
Magnetic fields are generated by the charged electron and nucleus moving around each other, as described by the orbital magnetic moment. The electron is itself like a little bar magnet, and its spin magnetic moment interacts with these orbital magnetic fields, and vice-versa.
Describe the Darwin term.
The electron is constantly buffeted by electron-positron pairs appearing out of the quantum vacuum. The effect of this movement is to smear out the potential that the electron effectively “sees”. In the hydrogen atom, this effect is only important when the electron is very close to the nucleus.
Describe the Lamb shift.
There are a degeneracy of states with the same j. In reality these states are split. This is caused by the electron and the photon emitting and reabsorbing virtual particles on short timescales.
Describe Hyperfine correction.
The interaction of the orbital spin and magnetic moments. This leads to a tiny energy difference when the nuclear and electronic spins are aligned.
What are the two external perturbations?
The zeeman effect and the stark effect.
Describe the Stark effect.
The stark effect is the hydrogen atom’s orbital response to the external electric field.
Describe the Zeeman effect.
The Zeeman effect is the hydrogen atom’s orbital response to the external magnetic field.
Describe the Lande g factor.
A measure of how much the energy of the hydrogen atom shifts under a weak magnetic field compared to the classical expectation for an electron being whizzed around a string with z-component of total angular momentum.
Describe Pauli’s exclusion principle.
Pauli’s exclusion principle states that no two electrons can occupy the same state.
Describe Ionisation energy
Ionisation energy – Eion, the minimum energy required to remove an electron. Eion grows until the noble gases.
Describe electron affinity,
Electron affinity is the minimum energy released when adding an electron. Eaff grows until the halogens.
