Chapter 16 and 17 Flashcards Preview

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Flashcards in Chapter 16 and 17 Deck (24):
1

most commonly used IR region

mid-IR, 2500 to 15000

2

when frequency of radiation matches the vibrational frequency of a molecule..

absorption occurs, changing the amplitude of the dipole moment

3

Ir plots ? vs ?

%t vs wavenumber

4

IR bands for linear molecule

3N-5

5

IR bands for nonlinear molecule

3N-6

6

Less bands produced in IR if

symmetry of molecule produces no change in dipole. energies of two vibration nearly identical

7

? can stick to gold

thiols

8

advantages of fourier transform IR spec

fast scanning, high res, surface confined materials, IR emission

9

IR sources produce ? radiation. Similar to ?

continuum. blackbody

10

max IR radiation at ?

5900 cm^-1

11

Ir sources consist of an inert solid heated to ?

1500K

12

three types of Ir sources

Nernts glower, Globar, CO2 laser

13

nernst glower

rare earth oxides in cyllinder

14

globar

silicon carbide rod

15

CO2 laser tuning range

900 to 1100 cm^-1

16

two types of IR transducers

MCT and DTS

17

MCT

mercury cadmium telluride. semiconductor. absorbs radiation and promotes valence electrons to higher energy. high conductivity, low resistance. fast and sensitive. 1000-4000cm^-1

18

DTS

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.

19

solvents in mid-IR may have large IR bands. compensated for by?

subtracting out solvent blank

20

group function region?

3600 to 1250 cm^-1

21

fingerprint region?

1200 to 600 cm^-1

22

? identifiers are present in fingerprint region

halogen

23

Specular reflection

IR hits sample at an angle. output reflection vs wavelength

24

Attenuate total reflectance

good for samples that are difficult to deal with. sample is placed on opposite side of transparent crystalline material of high refractive index. adjust incident angle. multiple internal reflections before passing to detector.