Flashcards in Chapter 16 and 17 Deck (24):
most commonly used IR region
mid-IR, 2500 to 15000
when frequency of radiation matches the vibrational frequency of a molecule..
absorption occurs, changing the amplitude of the dipole moment
Ir plots ? vs ?
%t vs wavenumber
IR bands for linear molecule
IR bands for nonlinear molecule
Less bands produced in IR if
symmetry of molecule produces no change in dipole. energies of two vibration nearly identical
? can stick to gold
advantages of fourier transform IR spec
fast scanning, high res, surface confined materials, IR emission
IR sources produce ? radiation. Similar to ?
max IR radiation at ?
Ir sources consist of an inert solid heated to ?
three types of Ir sources
Nernts glower, Globar, CO2 laser
rare earth oxides in cyllinder
silicon carbide rod
CO2 laser tuning range
900 to 1100 cm^-1
two types of IR transducers
MCT and DTS
mercury cadmium telluride. semiconductor. absorbs radiation and promotes valence electrons to higher energy. high conductivity, low resistance. fast and sensitive. 1000-4000cm^-1
deuterated triglyceride sulfate. pyroelectric wafer insulator. electron field polarizes and material holds that polarization based on temperature. slower than MST but measures in Mid-IR.
solvents in mid-IR may have large IR bands. compensated for by?
subtracting out solvent blank
group function region?
3600 to 1250 cm^-1
1200 to 600 cm^-1
? identifiers are present in fingerprint region
IR hits sample at an angle. output reflection vs wavelength