Frequently Asked Questions
Q. Why do the amplitudes of fluorescence spectra change with integration time in Setup mode but not in Data Acquisition mode?A. Setup shows raw detector signals accumulated over the specified integration period. But the spectra in Data Acquisition are scaled to the specified integration time and display as emission per unit time. These amplitudes are characteristic of the sample rather than the experimental conditions.
Q. Why does my Graphene Sheet results plot look odd?
A. Deduced (n,m) distributions are sensitive to the fitting process and can be distorted by relatively small fitting errors. A suitable parameter template, experience with parameter control, and patience in spectral fitting are generally needed to obtain Graphene Sheet plots that reflect proper (n,m) distributions.
Q. My NS1 is equipped with the visible absorption option, but there are small discontinuities at the point when the visible and near-IR segments meet. Why?
A. A major cause can be sample cell path lengths that differ from their nominal values. In a standard 10 x 4 mm sample cell, the 10 mm dimension is accurate but the 4 mm dimension may not be. To account for this, enter slightly adjusted values for the visible (second) path length into the Absorption Configuration dialog box until the two segments match. If you are using disposable plastic sample cells, the mismatch may be more severe and variable because of refractive displacements caused by uncontrolled window angles along the visible path.
Q. Can I re-analyze data from an old file?
A. Yes. Just load the old file into the file name box on the main acquisition screen, select the type of fit to perform, and hit Start.
Q. I need to detect SWNTs with the highest possible sensitivity, without doing a detailed compositional analysis. What's the best approach?
A. Go into Setup mode and measure emission data while exciting the sample with all laser wavelengths at once. Of course, long integration times and a lot of averaging should be used, too.
Q. How can I get the lowest noise level for near-IR absorbance measurements?
A. Take the sample spectrum as soon as possible after the reference spectrum. As the delay between them increases, mechanical relaxation processes in the two optical fibers connecting the Main Optical Unit to the Spectrograph Unit cause spectral mismatches that show up as noise. For the best absorbance performance, be sure that these optical fibers remain physically stationary and untouched.