CHEM 4502 Lecture Notes - Lecture 14: Globar, Stokes Shift, Hydrogen Cyanide
Document Summary
Midterm 2: on ch 4 and 5not cumulative, but material builds on itself. Which of the following diatomics will be ir active? the derivative can"t be 0 integral gives selection rule dipole is along bond direction. For polyatomic molecules we can consider each of the nvib vibrational degrees of freedom as independent harmonic oscillators. We refer to the characteristic independent vibrational motions as normal modes. Since normal modes = independent, energy is just sum: For example, water has 3 normal modes: 3n - 6 = 3 bend (like flapping wings): 1595 cm-1 symmetric stretch: 3686 cm-1 asymmetric stretch: 3725 cm-1. The dipole now depends on displacement along each of the normal coordinates, qi: The transition dipole moment for excitation of a single mode: : for mode to be ir active, dipole must change with motion along normal coordinate. Ir spectroscopy: co2 look at spectrum on slide.
