4/23/24 Flashcards
(20 cards)
what is collisional broadening
the time between the collisions affects the excited state lifetime
when there is a short time between collisions, how is the peak width affected
the peak will be wider and more broad
when there is a long time between collisions, how is the peak width affected
the peak width will be more narrow and small
for a gas sample, how is the peak width affected for a higher pressure sample?
the collisional frequency is increased, the time between collisions is decreased so there is a larger/broader peak width
for a gas sample, how is the peak width affected for a low pressure sample
the collisional frequency is decreased, the time between collisions is decreased so there is a narrower/smaller peak width
between liquids and gases, how do they differ in terms of collisional broadening
liquids will have a higher collisional frequency, therefore less time between collisions and more collisional broadening
gases will have less collisional frequency, therefore more time between collisions and less collisional broadening
for the doppler effect, how does the observed frequency of a molecule vary when the molecule is moving away from the detector?
the observed frequency is less than the emitted frequency
for the doppler effect, how does the observed frequency of a molecule vary when the molecule is moving toward the detector
the observed frequency is greater than the emitted frequency
for molecules at higher temperatures, how is their doppler broadening affected?
the molecules move faster so there is larger doppler broadening
for molecules at lower temperatures, how is their doppler broadening affected?
the molecules move slower, so there is a smaller doppler broadening
do liquids or gases have more doppler broadening? Why?
gases have more doppler broadening because they have longer distances between collisions
liquids have less doppler broadening because they have shorter distances between collisions
how is the doppler effect related to the speed of the molecule
it is proportional to it
what is the rigid rotor model
we assume the bond length does not change during rotation
is the ground state energy for rotational motion non zero?
no, it is zero
which molecules give a rotational spectrum
polar molecules like H2O, CO, and NH3
which molecules are not rotationally active
nonpolar molecules like CO2, N2, C2H2
how many transitions can occur for a rotational spectrum
there is a limited number of transitions possible, the molecule can only go up or down 1 energy level
how do the energy requirements for an absorption or emission transition compare?
you require more energy to go up a level than down a level, the energy levels are not evenly spaces
for the energy levels of rotation, are the energy levels the same?
no, to go up a level at different transitions, it requires different amounts of energy
