L2 Rich: ir spectroscopy part 1 Flashcards Preview

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Flashcards in L2 Rich: ir spectroscopy part 1 Deck (24):
1

what does IR stand for?

infrared spectroscopy

2

what is shot through a sample?

IR radiation

3

what do molecules absorb and what does this promote?

absorbs certain frequencies which leads to a higher vibrational energy level

4

Historically IR spectra are shown as ______

transmission

5

Spectra can be plotted as _________

absorption

6

what can IR spectroscopy be preformed on?

Solids, Liquids and Gases

7

what type of techniques an be used on solids?


•KBr disc
•Nujol mull
•Attenuated Total Reflection (ATR)

8

what type of IR be done on liquids?

•Salt plates
•Attenuated Total Reflection (ATR)

9

what type of IR be done on gases ?

gas cell

10

how does sample preparation for KBr disc work?

solid sample ground with dry KBr
placed in mould and compressed
KBR shows cold flow and forms transparent disc

11

what are some issues with KBr?

fragile and difficult
sample recovery difficult

12

does KBr absorb IR?

no

13

how does sample preparation for Nujol mull work?

- sample ground and dispersed in mineral oil
- mixed
thin layer spread between polish sodium chloride plates

14

How many absorption bands does Nujol have?

3 major bands

15

Possible to run in _______________ as a supplement

hexachlorobutadiene

16

How is sample recovery with the Nujol Mull preparation?

difficult

17

whats used to analyse liquids?

two dismountable IR windows

18

what does qualitative analysis of liquids involve?

a drop of sample compressed between two NaCl or KBr discs without spacers to create a film

19

can salt plates be used for aqueous samples?

no

20

Quantitative analysis uses cells with?

a variable or fixed path length

21

Absorbances for gases can be weak, this means what is needed?

a long pathlength is often needed

22

what is needed for IR on gas cell?

- Glass gas cell with non IR absorbing windows at each end
- Single crystals of NaCl, KBr, CaF2 or even CsI cut shape and polished
-Possible to also use balloons and gas sampling bags

23

why is low pressure needed when finding IR of gas cells?

to avoid interactions

24

start back at

ATR