I have been told that some compounds will react to laserlight but have no reaction to normal incandesant/florescent light --- I dont mean firing a 4kw
laser at something, the sheer heat and energy from that can cause practically anything to react. I'm talking about 200mw or less red bare-diode
lasers.
If this is true, what's the science behind it? does it have to do with the wavelength? the uniform dorection of the particles?Ozone - 19-8-2007 at 21:05
I'd think that intensity is not so much an issue as wavelength. So long as the wavelength is correct it (your photons) will be absorbed and something
will happen (be it dissipation of heat, singlet or triplet transitions, etc.). A compound readily absorbing at ~600nm will like your red laser diode
quite a bit. the laser has the advantages of being monochromatic (so, 200mW is 200mW of light that you want) and coherent (look it up).
For fun, also look up a very neat thing: it was observed that certain nanotubes (in bulk) will catch on fire if exposed to a photoflash. This was
discovered when a graduate student attempted to photograph the mass.
While you are at it, look up (well, quantum mechanics is a large field) UV-VIS, infrared, etc. spectroscopy (a detailed explanation of what happens
with irradiation at the continuum (look up) usually follows). MMM, ultraviolet catastrophe, black body radiation, electronic, vibrational and
rotational transition states, fluorescence, phosphorescence...
In otherwords, yes, it's true. Unfortunately, a complete answer to your question requires several years of chemistry and physics.
A more specific case might be helpful.
Cheers,
O3
[Edited on 19-8-2007 by Ozone]Faal - 20-8-2007 at 07:11
Specific case? dont have one, I was just following up on a rumor. I have a 200mw red diode laser and was curious if it had any practical application
in chemistry or if it reeally was nothing mroe than an 'expensive and dangerous toy' to expariment with light and optics.DrP - 20-8-2007 at 08:18
What is the wavelength of the light emited from your laser?Faal - 20-8-2007 at 09:17
Quote:
Originally posted by DrP
What is the wavelength of the light emited from your laser?
660nmfranklyn - 20-8-2007 at 09:24
Increasingly less common due to the advent of digital optical recording
silver halides which comprise photographic film are exquisitely tuned to
specific light frequencies for which the wavelength corresponds to the
particle size. This is why film development is done in a so called dark
room only illuminated with red light to which common film is insensitive.
.Ozone - 20-8-2007 at 19:22
660nm is not likely to do much. You really want something coherent at low wavelengths. Things start to get interesting ~380nm, and down.
Although, charge complexes absorb at 600-780nm...Irradiating the hell out of one of these in the presence of some substrate (other compound) might be
interesting--basically using a photosensitizer to transfer energy to an otherwise unreactive compound.
hmm,
O3not_important - 20-8-2007 at 20:43
Raman spectroscopy uses lasers these days. Shine a laser beam through a sample, catch off-axis scatter light and run it through a narrow band
blocking filter that blocks the laser frequency. Take the spectrum of the light that isn't blocked by the filter and you have something similar to
ordinary IR spectroscopy; the laser light is down-shifted (Stokes) or up-shifted (anti-Stokes) varying amounts depending on parts of the molecular
structure.
A diode laser might be a bit broad-band for this, unless you ran it through a narrow pass-band filter first. You do want a single spatial mode laser
for this to work well.
