Full set of Notes with Fill-Ins - San Jose State University

Chem 155 Unit 15 278 of 31617. A peak is observed in a fluorescence spectrometer whenanalyzing trace impurities in water. With the monochromatorexcitation source set to 250 nm, the mysterious weak peakappears at 274 nm, unusually close to the excitation band.When the excitation wavelength was changed to 300 nm, themystery bands moved to 335 nm.a. Calculate the Stokes shift for the mystery band in cm -1 forthe 250 nm excitation experiment.b. Calculate the Stokes shift for the mystery band in cm -1 forthe 300 nm excitation experiment.c. What might this ‘mystery peak’ be?10 7 10 7− = 3504250 27410 7 10 7− = 3483300 335The band moves with the excitation – it is the Ramanpeak for water OH stretch modes.Page 278 of 316