Introduction to Spectroscopy¶
Definition¶
Spectroscopy - The study of matter and it’s interaction with light, sound or particles (radiation)
- Can be through absorption, emission or scattering
What is light?¶
- Light is EM radiation, consisting of an electric field and a perpendicular magnetic field
- Light travels at varying speed through a medium, being energy/wavelength dependent
What is matter?¶
- A substance that has inertia and occupies physical space
- Made up of particles with different mass, charge and size
Postulates of quantum mechanics¶
- Particles can only exist in discreet states, determined by their amount of energy
- Interactions of particles cause energy to be emitted or absorbed
\[
\Delta E=E_{excited}−E_{ground}
\]
- The frequency \(\nu\) and wavelength \(\lambda\) of the radiation is related to its energy
\[
\Delta E=h\nu=\frac{hc}{\lambda}
\]
Energy states¶
- Energy states arise from molecular/atomic orbitals.
- The ground state is the lowest energy configuration of the compound
- As energy is increased, the electrons can jump into a higher orbital with a discreet amount of energy, in what’s called the excited state.
- Rotational/vibrational states arise from energy in the bonds of the atom itself
Waves¶
Consist of four properties:
- \(\nu\) frequency
- \(\lambda\) wavelength
- \(A\) Amplitude
- \(T\) Period
Expressed by the formula:
\[
y=A\sin\bigg(\frac{2\pi x}{\lambda} + 2\pi \nu t\bigg)
\]
Energy equation¶
Where:
- \(c=3\times10^8 m\cdot s^{−1}\)
- \(h=4.135\times 10^{−15} \text{ or } 6.626×\times10^{−34} J\)
\[
\Delta E=h\nu=\frac{hc}{\lambda}
\]
Wavelength¶
\[
\lambda=\frac{c}{n\nu}\approxeq\frac{c}{\nu}
\]
Wavenumber¶
\[
\bar{\nu}=\frac{1}{\lambda}
\]