<p>ME770; Fall 2007; Prof. Sanders; Homework #4; Due Oct 31, 2007</p><p>We wish to measure the rotational Raman spectrum of nitrogen in room air In particular, we will consider spontaneous anti-Stokes rotational Raman scattering. Here is a previous measurement from Drake et. al.:</p><p>We will assume:  532 nm, TEM00 laser is used for excitation (if you are interested in why one might choose 532 nm vs. other wavelengths, see http://homepages.cae.wisc.edu/~ssanders/me_770/homework_assignments/home work_4_wavelength_scaling_raman_spectrometer_considerations.xls)  300 cm-1 coverage (523.5 – 532.0 nm coverage)  1 cm-1 spectral resolution  a grating spectrometer, at least initially  max integration time 5 minutes  max spatial resolution 5 cm  max collection lens / mirror NA = 0.5  max grating size = 5 cm (groove length) x 10 cm  a 2-D Si CCD camera for collection, assumed to be arbitrarily binnable so we can achieve arbitrary pixel size/shape (max 25 mm x 25 mm)  considering the entire anti-Stokes branch, 168 pW are scattered uniformly into 4π Sr for every 1mm of propagation through room air for every 1 W of excitation power (see http://homepages.cae.wisc.edu/~ssanders/me_770/homework_assignments/HW_4 _raman_power_calculations_XA.xls)  11% of the scattered anti-Stokes light will be in the strongest line at room temperature (see http://homepages.cae.wisc.edu/~ssanders/me_770/homework_assignments/HW_4 _raman_power_calculations_XA.xls)  We require a signal-to-noise ratio of at least 20 on this strongest line</p><p> A Rayleigh/Mie/stray rejection filter (perhaps I2 gas cell) is available Your goal will be to design the spectrometer, then indicate what laser power you require.</p><p>Finally, try to use Renata’s paper (http://homepages.cae.wisc.edu/~ssanders/me_770/supplemental_material/SHS_OH_fla me_ApplOpt_revision_RJB.doc) to determine whether an interferometric spectrometer would offer better performance</p>