Very Rapid-Scan Time-Resolved FT-IR Spectrometry

This work was presented at the 2000 Pittcon Conference in
New Orleans, LA on March 16, 2000

Table of contents

Title Page

Picture of a Vibrational Spectroscopist on the Clearwater River

Outline

Conventional FT-IR spectrometer

Voice coil performance

Voice coil performance

Desired performance

Precessing Disk Interferometer

Top View of Rapid Scan Interferometer Breadboard Layout

Top View of Interferometer LN2 Cooled IR Detector

Top View of Laser and IR Sources w/ Suspended Beamsplitter

Stress: double-wedge

Two types of time-varying systems

Approaches to time-resolved IR spectroscopy

Scan time vs. modulation frequency

Dynamic range vs. scan time

Rapid-scan frequency spectrum

Retardation, velocity and duty cycle

Very-rapid-scan frequency spectrum

ADC resolution vs. frequency (1992)

ADC resolution vs. frequency (2000)

14 Bit 10 MHz ADC

Picture of Rapid Scan Interferometer Workstation

Picture of Disk Mirror and Drive Motor

Data acquisition

Bill Gate's Quote

Picture of Disk Motor Controller w/ Various Power Supplies and Function Generator

Instrument Specifications

Raw ADC output

Raw Infrared Data

Mirror Position vs. Time

Mirror Velocity vs. Time

Filtered Mirror Velocity

Signal Processing

Orthogonality of Components

Synthesized Interferogram

Lomb Periodogram of IR Signal

Lomb Periodogram of IR Signal

Theoretical SNR Performance (mid-IR)

Theoretical SNR Performance (NIR)

Actual SNR Performance (1997)

Actual SNR Performance (2000)

Estimate of Detector Bandwidth

Interferogram Noise Level

SNR performance

Single 50 ms Scan; SNR ~500:1

100% Line

Spectrum, 1.5 milliseconds, 8 cm-1

Picture of Chopper Wheel w/ Various Affixed Polymer Samples

Data of 85 Hz Chopper Wheel

5 ms Observation through Wheel

3 ms Scan Through Chopper

Conclusions

Acknowledgments

Contact Information

Author: Chris Manning
              Peter Griffiths
              Bryan Bowie

E-mail: chris@appl-tech.com

 
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