lasers

From: Michael Feldhaus (feldhaus@vengen.com)
Date: Wed Mar 24 1999 - 19:25:01 EST


Here is a question for the group.  We are currently using a Coulter
Elite ESP sorter with an air cooled argon laser and a water cooled Inova
90-5.  We are working with particles that have FITC and another similar
particle that has Rhodamine attached to the particle.  When we use our
air cooled laser at 10 mWatts of 488 we see about a three fold increase
in fluorescence of our rhodamine particle and about 2 log increase with
the FITC.  If I up the air cooled argon laser to 40mWatts we see a
100fold increase with the Rhodamine and a three log increase in
fluorescence with the FITC.  I assumed that the rhodamine, as well as
the FITC, was brighter simply because they were now absorbing more 488nm
light.  Here is my first question. Is our laser putting out only 488nm
light or are other wavelengths coming out as well (such as the 514 or
528 lines and are these wavelengths resposnsible for the rhodamnine
fluoresing brighter)???  As I understand lasers, the light output is
monochromatic and coherent. 

The second question:  I was thinking I could increase the fluorescence
of the Rhoadmaine by using a wavelenth of light closer to its excitation
maxima(around 550).   Therefore, i want to use the air cooled laser at
488nm and the water cooled innova 90-5 at 514 or 528.  Has anyone used a
488nm and a 514 or 528 at the same time?  Does it work well with the
gated amp?? Could I get by with just using the 514 for both fitc and
Rhodamine?  

I appreciate the input about the output:) Mike



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