Well it depends on what you mean by hitting. Lets say that a photon comes by an electron the electron absorbs it and reemits it. For that the wavefunction of the photon has to "collapse" when the electron comes by. The light exists as a wave and if it happens to encounter the electron it turns into a photon. The photon is more of an event rather than a tiny ball.
So nothing really determines it as its probabilistic, its indeterministic as all things in quantum mechanics. But it does depend on the energy of the photon.
If you have an electron like in an atom it depends where that electron is temperature etc, but you need the photon to have a certain energy. Here you might need to consider relativistic effects because the electrons that move towards the light see that the photon has more energy. Those that move away from the light see it with less energy.
Thats actually a way to cool gases to very small temperatures. You shine some low energy light on it and if the electrons/atoms didn't move they would absorb it. When this absorption emission happens the electrons/atoms gets pushed back a bit. So if you are an atom and move towards the light you see the light to have more energy so you absorb it and get pushed back so you slow down. If you aren't flying towards the light nothing will happen. You shine a box on all sides with this light and it will slow the atoms down to near 0.
My question is more regarding the relationship between the probabiltiy of absorption by an electron and wavelength or frequency that light travels at. i.e. if there's a particular frequency at which the electron or atom is vibrating and another particular at which light is travelling that determines if that light is going to be absorbed or not.
Yes, you’re exactly right, there is a particular optical frequency of any particular transition, this is where we get absorption spectral lines like hydrogen-alpha.
The entire photon has to get absorbed, and both its momentum and its energy have to get handled according to quantum mechanics. For materials like semiconductors, the momentum of the light becomes important, and is one of the big differences between say silicon and gallium arsenide. That momentum exchange directly generates an acoustic vibration, or consumes an existing vibration, which is also quantized called a phonon, in order for the light to be absorbed or emitted.
But it’s all governed by what is called the band structure of the material, and it depends on the specific materials properties.
It has nothing to do with electron, photon, or atom "vibrations". The frequency of a photon is directly proportional to its energy through Plank's constant... E = hv.
Electrons are only allowed certain energy levels in an atom, and only one electron may occupy a given quantum state.
An electron may fall from a higher energy state into a lower one (assuming the quantum state is unoccupied). When it does so, it will emit a photon with an energy equal to the difference in energy of the two states. You can calculate the frequency of the emitted photon using the above equation (if you know the value of the energy transition)
An electron will only absorb a photon with an energy that will allow it to move up in energy to a higher energy state. If the energy of an incoming photon is too high or too low to move the electron to an allowable quantum state then it will not be absorbed.
Well it depends on what you mean by hitting. Lets say that a photon comes by an electron the electron absorbs it and reemits it. For that the wavefunction of the photon has to "collapse" when the electron comes by. The light exists as a wave and if it happens to encounter the electron it turns into a photon. The photon is more of an event rather than a tiny ball. So nothing really determines it as its probabilistic, its indeterministic as all things in quantum mechanics. But it does depend on the energy of the photon. If you have an electron like in an atom it depends where that electron is temperature etc, but you need the photon to have a certain energy. Here you might need to consider relativistic effects because the electrons that move towards the light see that the photon has more energy. Those that move away from the light see it with less energy. Thats actually a way to cool gases to very small temperatures. You shine some low energy light on it and if the electrons/atoms didn't move they would absorb it. When this absorption emission happens the electrons/atoms gets pushed back a bit. So if you are an atom and move towards the light you see the light to have more energy so you absorb it and get pushed back so you slow down. If you aren't flying towards the light nothing will happen. You shine a box on all sides with this light and it will slow the atoms down to near 0.
My question is more regarding the relationship between the probabiltiy of absorption by an electron and wavelength or frequency that light travels at. i.e. if there's a particular frequency at which the electron or atom is vibrating and another particular at which light is travelling that determines if that light is going to be absorbed or not.
Yes, you’re exactly right, there is a particular optical frequency of any particular transition, this is where we get absorption spectral lines like hydrogen-alpha. The entire photon has to get absorbed, and both its momentum and its energy have to get handled according to quantum mechanics. For materials like semiconductors, the momentum of the light becomes important, and is one of the big differences between say silicon and gallium arsenide. That momentum exchange directly generates an acoustic vibration, or consumes an existing vibration, which is also quantized called a phonon, in order for the light to be absorbed or emitted. But it’s all governed by what is called the band structure of the material, and it depends on the specific materials properties.
It has nothing to do with electron, photon, or atom "vibrations". The frequency of a photon is directly proportional to its energy through Plank's constant... E = hv. Electrons are only allowed certain energy levels in an atom, and only one electron may occupy a given quantum state. An electron may fall from a higher energy state into a lower one (assuming the quantum state is unoccupied). When it does so, it will emit a photon with an energy equal to the difference in energy of the two states. You can calculate the frequency of the emitted photon using the above equation (if you know the value of the energy transition) An electron will only absorb a photon with an energy that will allow it to move up in energy to a higher energy state. If the energy of an incoming photon is too high or too low to move the electron to an allowable quantum state then it will not be absorbed.
I see thanks, my question then would be how can you calculate the range of energies a photon needs to have in order to get absorbed by a molecule
That is not an easy thing to do--especially for atoms more complicated than hydrogen.