[RASMB] Intensity of the Xenon flash lamp

Borries Demeler demeler at biochem.uthscsa.edu
Mon Jul 12 12:24:00 PDT 2004


Karel,

there may be a problem with the monochromator or the data acquisition
board.  The wavelength should not change by itself if you leave it
constant throughout the run. See if Beckman Service would be willing to
loan you a different monochromator to see if the problem goes away. About
the intensity: Does your data look noisy? When I fit equilibrium data
from 230 nm between 0 and 0.9 OD I get a variance of ~ 1e-5 - 2e-5 for
a good fit. What do you get?

-Borries

> 
> Dear AUC user,
> Because various people say different things about what the intensity of the
> 229/230 nm peak in the Xenon flash lamp emission spectrum should be: some
> say it should be above 15.000, other say it should be above 4000 and the
> Beckman instruction manual says above 6000 (a graph is shown with an
> intensity of around 36.000), I would like to ask you what should it be and
> how do I check my Signal to Noise ratio? Our intensity at 229 nm in the
> emission spectrum of the Hamamatsu L 2435 '96-09 Xenon lamp is somewhat
> below 6000, which was recorded at 5.9, 6.5, and 7.1 cm from the axis of
> rotation through a windowless cell.
> The service engineer is not willing to do anything about it because
> according to him (and others he got in contact with) the intensity is within
> the machines limitation as long as it is above 4000 @ 229 nm! So what should
> I do (the lamp was cleaned over and over again as well as the slit
> assembly)? Another problem we experience is that sedimentation velocity
> profiles jump around despite that theyu are recorded at the same wavelength!
> I would like to know if anyone has seen this before and more important how
> can I solve my problem?
> 
> Thank you for your time and I will eagerly await your reply,
> 
> Karel Planken.
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