1	Biophotonic Detection of N2 Tilden Hagan
2	Goal Precise detection of Nitrogen – N2 Preferably in living tissue Otherwise in solution or gaseous
3	The Bends Nitrogen buildup in the body increases with pressure, from depth If too much N2 is absorbed into the body, when the diver surfaces bubbles can form inside the body - just like carbonation when opening a can of soda The bends can be fatal in severe cases
4	Methods Used Absorbance In solution with white light Gaseous with white light, Ti-Saph laser, and HeNe laser Two photon with Ti-Saph laser Raman Scattering Gaseous with Ti-Saph laser and HeNe laser Both lasers also with acetone and ethanol
5	Absorbance Absorbance in Solution Bubbled pure N2 through water to increase the N2 absorbed by water Measured the spectrum of transmitted white light before and after increasing N2 levels
6	Ti-Saph Absorbance Absorbance Gaseous Measured the power of transmitted Ti-Saph laser beam at different wavelengths with atmospheric air and high pressure N2
7	Ti-Saph Two Photon Absorption Two Photon Absorption Two photons absorbed at almost the same moment, by one atom, excite it to an energy state equivalent to a single photon with twice the energy (half the wavelength) Focused Two Photon Gaseous Absorbance Focused laser beam in cell to induce two photon absorption and measured transmitted power
8	Raman Scattering Inelastic scattering of light A monochromatic light source excites the molecules Most of the absorbed energy excites electrons, but some causes vibrational motion or rotation This induces a virtual state where the electron resides, when it settles the emitted photon is at a different wavelength Stokes Raman Scattering will cause the photon to be at a higher wavelength (lower energy), equivalent to the energy lost in the vibrational transition Anti-Stokes Scattering will cause the photon to be at a lower wavelength (higher energy), due to the already vibrating molecule adding the additional energy to the emitted photon
9	Raman Scattering Ethanol and Acetone Excite with a 632nm HeNe laser to observe raman shifts
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12	"Acetone raman in quartz cuvette" Acetone raman in quartz cuvette Listed peaks are at 1700, 2950 cm-1 http://www.deltanu.com/labs/dnlab2.pdf http://www.deltanu.com/presentations/acswork2.pdf
13	Raman Scattering Nitrogen Excite with a 632nm HeNe laser to observe raman shifts
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15	Conclusion Research should continue on accurate nitrogen detection because it could be very useful in some applications. However, nitrogen’s symmetric nature and lack of a dipole makes detection very difficult We were unable to successfully detect N2 using any of the described methods Reasons for this include not having a sensitive enough spectrometer, or one with a tight enough bandwidth Interference from the strong raman spectra of glass Future Work Use a quartz cell instead of glass Build a better spectrometer suited for this specific task so the raman signal from nitrogen could be detected
16	Acknowledgements I would like to extend a thank you to my project advisor Adam Wax for the opportunity to conduct this research project I would also like to thank Nick Graff for the tremendous amount of time and help he gave me over the past two semesters This project was supported in part by NSF (BES 03-48204)