Fourier transform infrared spectroscopy

Berezin DanilaMoscow 2013

Plan of a journey

Terahertz radiation

Its application

And research

FTIR spectroscopy

Terahertz radiation is an electromagnetic waves

Terahertz gap1011 – 1013 Hz

THz technology brings better sensing capabilities

cancer

cavity

Visible image THz image

THz technology brings better sensing capabilities

Visible image THz image

ceramicknife

The goal is to measure how well a sample absorbs light

sample light

Scanning spectroscopy is the most straightforward way

goal – spectrumof absorption

beam source sample detector

abso

rptio

n

It shines a monochromatic light beam…

beam source sample detector

abso

rptio

n

…and measures how much is absorbed

FT spectroscopy is a less intuitive way to obtain the same information

goal – spectrumof absorption

beam source sample detector

abso

rptio

n

beam number

A beam contains many frequencies of light atonce and absorption of that beam is measured

beam source sample detector

abso

rptio

n

beam number

Next, beam is modified to give a second data point

beam source sample detector

abso

rptio

n

beam number

Process is repeated many times

Afterwards, computer processing is required

There are still undiscovered nuances

How to generate and modify that special beam?

What computer processing is required?

moving mirror

Wave interference is a key to generate that special beam

Michelson interferometer

light source

beam for theexperiment

Processing required is Fourier transform

raw data desired result

FT spectroscopy has an advantage – Fellgett’s advantage

Scanningspectroscopy

Fourier transformspectroscopy

FTIR spectroscopy

– Possible applications– Technology– Advantage

Thank you

Back up

Fourier transformmirror 1

mirror 2

y1/2x/2

Monochromatic source

Polychromatic source

Fourier transform

Fourier transform