Infrared Spectroscopy Flashcards
Infrared Process
Molecular Vibration
- Bond Stretching
- Bond Bending
As covalent bond oscillates due to oscillation of dipole of the molecule, ____ is produced
varying electromagnetic field is produced
The greater the dipole moment change through vibration, the ___ the EMF that us generated
more intense
when a wave of IR light encounters this oscillating EMF, the waves ___ and IR light is ___
coupled; absorbed
Coupled wave vibrates with ___ the amplitude
twice
Type of bond stretching
Symmetric and asymmetric
Types of bond bending
in-plane rocking
in-plane scissoring
out-of-plane wagging
out-of-plane twisting
a molecule can vibrate in many ways, and each way is called ___
vibrational mode
Vibrational modes for
linear?
non linear?
linear: 3x-5
nonlinear: 3x-6
Basic Instrumentation (IR)
Radiation source
Sample Holder
Wavelength Selector
Detector
inert solid that is electrically heated to a temperature between 1500 to 2200 K
blackbody sources
Common blackbody sources
Globar
Nernst Glower
Incandescent Wire Source
*** (others)
CO2 laser
Mercury Arc Lamp
Tubgsten Halogen Lamp
:rare earth oxides (Ze, Ce, Th) heated electrically formed into a cylinder having a diameter of 1 to 2 mm
: with platinum leads
Nernst Glower
Uses silicon carbide rod; water cooling is needed; more expensive
Globar
:lower intensity but longer life than globar and nernst glower
: a tightly wound spiral of nichrome wore or rhodium-wire heated to about 1100K by an electrical current
incandescent wire source
for far-infrared region; quartz-jacketed tube containing mercury vapor at a pressure greater than one atmosphere
Mercury Arc Lamp
CO2 laser consists of
70% He, 15% CO2, 15% N2
Liquid sample cells can be sandwiched using liquid sample cells of highly purified ____, such as ___
alkali halides; NaCl, KBr, CaF2
_____ cannot be used because they cannot dissolve alkali halides
Aqueous solvents
For most liquids, the sample cell thickness is ___
0.01-0.05 mm