IR spectroscopy - long process??

[kenhung123]

In the book, they say there is a wavelength selector (monochromator) in the spectrophotometer in IR spec. Does that mean we need to pass every single wavelength separately through the sample?

I would also like to ask, what does the vibrational energy got to do with IR spec? Is it simply to explain the reason for absorption or does the detector actually detects the degree of vibration and calculate the absorption?

[crayolé]

Yeah, every wavelength is passed through, thats how you get the different readings (wave numbers)

Hmm, i thought vibrational energy was to do with NMR? Anyway, I guess infared deals with the amount of vibration caused when the bonds are stretched and bent as each bond will vibrate to a different degree.

Don't quote me on any of this though, I'm just getting my head around it too ;]

[m@tty]

NMR has to do with the 'spin' of the nucleons within each atom, whereas IR is concerned with changes in the bonds between atoms such as bending twisting stretching etc.

[kenhung123]

Yea but does the detector detect the stretching and bending of bonds or the energy absorbed?

[fady_22]

The detector detects transmittance, that is how much light gets through. So it ultimately measures how much light has been absorbed by the sample.
How would it be able to detect the bending and stretching anyway?

[kenhung123]

No idea, so does it pass a wavelength per time..?