$$ c=λν $$
$$ c= \text {speed of light}= 2.99\times 10^8 \text{ m s}^{-1} $$
$$ E=hν $$
$$ h=\text{plancks constant}= 6.626\times 10^{-34} \text{J s} $$
we can use different strength electromagnetic radiation to perform different functions on molecules. the function will depend on the energy and thus the λ and ν
| molecular transition | energy range/ $kJ\; mol^{-1}$ | corresponding radiation |
|---|---|---|
| electronic transitions | 50-1000 | ultraviolet and visible |
| bond vibrations | 1-50 | infrared |
| molecular rotations | 0.01-1 | microwaves |
| electron spin | $5\times 10^{-4}$ - 0.01 | microwaves |
| nuclear spin | $1\times 10^{-6} - 1\times 10^{-4}$ | x-rays |
when mr de Broglie quantified the wave particle duality of an electron, he also did so for everything else ever
$$ λ=\frac{h}{mv} $$
in an atom, electrons are confined to a certain wavelength so that they fit into the relevant space in the orbitals.
this means only certain wavelengths are allowed and thus, as the only other variable, velocities
this shows how electrons in atoms are quantised into certain energies. we can exploit this quantisation by matching EM radiation to the gaps between quantised levels to see if we can get them to jump up a level
once we know the possible energies of an electron, or other thing, we can use the Schrödinger equation to find the relevant wavefunction, Ψ. the wavefunction can then be squared to find the probability of finding an electron in a particular position at a given energy state
for some reason, if we sum all the different energies we can get the total energy, i don’t even understand what the energy is of though
$$ E_{\text{total}}=E_{\text{electronic}}+E_{\text{vibration}}+E_{\text{rotation}}+E_{\text{translation}} $$
the total energy is the energy of the molecule and each individual one shows something that stores energy within the molecule
when exposed to the right energy radiation, molecules will transition to an excited state. you can either plot the radiation absorbed by the sample or you can plot the radiation that made it through the sample
in absorbtion, peaks rise up form the bottom as those are the energies at which radiation was absorbed
in transmission spectra, the peaks coem from the top down, s this energy of radiaion did not make it through the sample and is lower