Card Set Information
Inst390 sait clt2
Main terms and acronyms related to spectroscopy
A tungsten source produces light in the _____ range
A deuterium source produces light in the _____ range
Is the intensity of the light produced by a light source the same for each wavelength region it covers?
No. The intensity varies with wavelength
The cathode of a PMT is coated with a _____ material which emits electrons when struck by a photon
What kind of electrons does UV light interact with?
Which has higher energy: bonding or anti bonding molecular orbitals?
MO with single bonds
MO with double bonds
An asterisk * is used to denote
Anti bonding orbitals
Non bonding electrons
Which type of transition tends to have smaller epsilon values?
N transitions (non bonding electrons jumping up)
Highest occupied molecular orbital
Lowest Unoccupied Molecular Orbital
The most important transition is typically the one with the (highest/lowest) energy
What are the characteristics of molecules that can have an n to pi* transition?
They all have pi bonds and non-bonding electrons (ex. C=N, C=O, C=S)
A functional group that absorbs light and contributes to a molecule's color
A group which affects how a chromophore absorbs (give the name and an example of one)
: OH, halogens
The shift of absorption to a longer wavelength (red shift)
The shift of absorption to a shorter wavelength (blue shift)
When an auxochrome increases absorbance, this is called
When an auxochrome decreases absorbance, this is called
Choose your solvent carefully because it can affect:
The sharpness of peaks (polar solvents cause band broadening)
The wavelength of maximum absorbance
Charge Transfer Complex is another name for
A coordinate covalent compound
If you have two species that absorb at the same wavelength, what are two options for analysis?
Use a masking agent
Use simultaneous equations
A name for a double beam technique where you measure the difference in absorbance between two samples
Difference Spectrometry (see slide 55)
The name for titrations using spectrophotometry to detect the endpoint
When the actual absorbance is less than that predicted by Beer's law, this is called
Random thermal motion of electrons in the detector is called
Johnson's noise is typically more of a problem with
Movement of electrons in detector between anode and cathode without any incoming stimulation
Signal shot noise
The term for noise that occurs when the light source fluctuates
Two options to improve signal-noise ratio