(23) Physical basis of spectroscopy Flashcards
what is absorption?
a molecule absorbs the energy of a photon that moves from a low energy state to a high energy state
what is emission?
a molecule emits energy as a photon of EM radiation as it falls from a high energy state to a lower energy state
What energy is measured in radiowave spectroscopy?
Nuclear and electrical spin states (NMR)
What energy is measured in microwave spectroscopy?
Rotational modes
What energy is measured in IR spectroscopy?
Vibrational modes
What energy is measured in (UV) visible spectroscopy?
Valance electron orbitals
What energy is measured in X-Ray spectroscopy?
Core electron orbitals
What energy is measured in gamma-ray spectroscopy?
Nuclear energy levels
What is emission spectroscopy?
- Particle must be in excited state
- Excitation into the state can be thermal or electric energy
- When the particle relaxes, photon is emitted
- Photon energy is equal to the energy gap between initial and final states
How do we identify the frequency of photons during emission spectroscopy?
By identifying the colour
What does an atomic nucleus require to have nuclear spin?
An odd number of protons and neutrons
What does NMR spectroscopy measure ?
Measures the absorption of nuclei as they flip from low to high energy levels
name two ways of exciting an electron to an excited state
thermal or electronic energy
how can we calculate energy from hv
(delta)E = Eupper - Elower = hv
the energy of a photon of EM radiation can be calculated by calculating the difference in energy from the upper and lower energy level
what are the conditions of absorption and stimulated emission?
nlower>nupper = absorption
lower
