Lab9. Prelab Questions.

Questions you NEED to answer in a written form before the Lab in your notebook. 

• How many normal vibrational modes are in CO₂, and C₂H₂ molecules? Which of them do you expect to see in IR absorption? in Raman spectra?
• Calculate B_e for ground state of ¹²CO₂, H³⁵Cl, D³⁵Cl, ¹²C₂H₂ and ¹²C₂D₂ using Eq.(6) in its convenient explicit expression:

  Be =	h		16.8576314	cm-1
  		=
  	8p2Ic		I(amu Å2)

  where masses are measured in atomic units and distances in Å ( 1Å = 10^-8 cm). Take for CO₂: r_CO = 1.16 Å; for HCl: r_HCl = 1.275 Å, for acetylene: R_CC = 1.2024 Å, R_CH = 1.0625 Å. Masses in atomic units are: H = 1.007825; D = 2.014102; ³⁵Cl = 34.968853. Use either Eq.(4) or (24) for calculation of I.

•  

What kind of questions you MAY be asked before the Lab.

• Explain Eq.(5) in introduction: which terms correspond to the energy of a harmonic oscillator, a rigid rotor, anharmonicity, centrifugal stretching, and the interaction between vibration and rotation.
• Describe the selection rules for vibration-rotational transitions
• What is an overtone, a hot band and a fundamental transition?

Last updated on 04/19/99
Email: snsm@nmsu.edu