Spectroscopy Flashcards
spectro-
to look
photo
light
metry-
to measure
scopy
to examine
is spectrophotometry quantitative?
yes
spectroscopy is qualitative?
yes
highest to lowest energy light forms
Highest Energy: gamma rays
x-rays
UV
visible (V I B G Y O R)
IR
microwave
Lowest Energy: radio
relationship between energy, frequency, and wavelength
high energy = high frequency = low wavlength
nu = c / lambda
frequency = c over wavlength
absorption of energy outcomes: removal of an electron, rotational excitation, vibrational excitation, electronic excitation ranked requiring most energy to lowest energy
Needs Most Energy: removal of an electron
electronic excitation
vibrational excitation
Needs Least Energy: rotational excitation
Where does electronic excitation happen?
UV-Vis
where does vibrational excitation happen?
IR
where does rotational excitation happen?
Radio
Which transition involves a relaxation that does not give off either a photon or heat?
vibrational relaxation, it can disperse the energy throughout the molecule through it bond vibrations
similarities and differences of fluorescence and phosphorescence
both absorb photons, vibrational relaxation, then emit photons of a lower E
fluorescence emits from a singlet state + has no change in spin state, phosphorescence has an intersystem crossing from singlet to triplet, emits from a triplet; fluor. has faster time scale than phosph.
ground state + photon = excited singlet state
absorption
excited singlet state = ground state + photon
fluorescence / emission
excited singlet state = ground state + heat
internal conversion
excited singlet state = excited triplet state + heat
intersystem crossing
excited triplet state = ground state + photon
phosphorescence / emission
excited triplet state = ground state + heat
intersystem crossing
which transitions require a change in electron spin?
phosphorescence and intersystem crossing; T to S or S to T
For any fluorescence or phosphorescence process; which part involves higher energy?
absorption requires higher energy / shorter wavelength
emission involves lower energy / longer wavelength as there is a reduction of energy that occurs through vibrational relaxation between absorption and emission
the difference in energy b/w ground and excited states varies based on the structure of the molecule; how does this affect absorption of the molecule?
differences in band gaps lead to different amount of energy required for the absorption transition to occur, each molecule will have different wavelengths where it is more likely to absorb
what are the nonradiative types of transitions?
vibrational relaxation, internal conversion, and intersystem crossing
which transitions involve photons?
fluorescence, phosphorescence, and absorption
which transition has a change in spin state: intersystem crossing or internal conversion?
intersystem crossing
