Optical Instrumentation
IMSERC houses all of the spectrometers used in the undergraduate teaching laboratories. These instruments have primarily been purchased to support the undergraduate classes, but are typically used heavily for only 4-5 weeks out of the year. The instruments are made available to the NU community when not in use for the classes. Other facilities maintain optical characterization instrumentation including NUANCE-KeckII and Keck Biophysics. Last year, Keck Biophysics (KBP) purchased a new UV-Vis spectrometer using core facilities funding, so new users of UV-Vis are now being directed to that facility. Due to the high time requirement needed to keep the IMSERC instrument running, new users are directed to KBP’s instrument.
Instrument |
Wavelength |
Sample Type |
Information |
PTI Spectrofluorimeter |
100-900 nm |
liquid/solution |
Electronic Structure |
Bruker Tensor 37 FTIR |
400-8000 cm-1 |
KBr pellet / liquid / Solid / Gas |
Bonding Structure |
Delta Nu Raman |
685nm excitation |
solid / solution |
Bonding Structure |
Instrumentation
PTI Flourimieter:
Photon Technology International model QM-2 is a modular spectrofluorimeter for recording excitation or emission spectra, synchronous scans, and lifetime phosphorescence studies. It is equipped with two lamps--a 75 watt Xenon arc lamp, used in steady state measurements, and a pulsed lamp, used for phosphorescence or gated and delayed fluorescence measurements. The system allows for addition and subtraction of data, spectral correction and output of files in ASCII and binary forms. The instrument ccepts 2mL samples. Excitation and emmission measurements from 190 -900 nm can be performed.
Bruker Tensor 37 FTIR Spectrometer
The Bruker Tensor 37 FTIR Spectrometer is equipped with an Mid IR detector and KBr beamsplitter for use between 400 and 7000 cm-1. Sample can be analyzed using the ATR attachment, a gas cell or by pressing KBr pellets. In addition to the Bruker software a ~50,000 sample library aids in the interpretation of spectra and identification of unknowns.
Raman vs FTIR
Raman and FTIR are generally complimentary techniques. IR selection rules require a change in electric dipole moment vs bond distance and have stongest signal when two atoms in a molecule have very different electronegativities. Raman selection rules require a change in polarizability vs bond distance. This difference in selection rules leads to many molecular vibrations that are IR inactive, but Raman active. For instance, many highly symmetrical vibrational modes result in no change in dipole and are IR inactive, but are Raman active
Delta Nu Raman Spectrometer
The DeltaNu Raman system uses a 785 nm CW laser and has a spectral range from ~200 to 2000 cm-1. The system is equipped with a polarizer and can be used with vials, NMR tubes and capllary tubes. The 785 nm laser was choosen as a compromise between optimizing sensitivity (Raman scattering increased with decreasing wavelength) and avoiding flourescence which overwhelms the Raman system. For systems which require very long collection times, users should switch to the NUANCE Raman microscope..
