Rotational and vibrating energy levels - find energy separation

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SUMMARY

The discussion focuses on calculating the energy separation between adjacent lines in the rotational-vibrational spectrum of H35Cl, given an equilibrium separation of 1.27 x 10-10 m. The relevant equation for energy, E = (n + 1/2)hω + h²/2I * l(l+1), is utilized, where I is the moment of inertia defined as I = μr2. The user contemplates simplifying the equation by assuming n = 0 and l = 0, while also seeking to determine angular momentum through frequency or force constant, which requires prior energy calculations.

PREREQUISITES
  • Understanding of quantum mechanics, specifically rotational and vibrational energy levels.
  • Familiarity with the moment of inertia and its calculation in molecular systems.
  • Knowledge of the principles of spectroscopy, particularly rotational-vibrational spectra.
  • Basic proficiency in using Planck's constant (h) and angular momentum concepts.
NEXT STEPS
  • Calculate the moment of inertia for H35Cl using I = μr2.
  • Explore the implications of selection rules in molecular transitions.
  • Learn how to derive frequency and force constants from energy levels in quantum systems.
  • Investigate the impact of temperature on the population of rotational levels in diatomic molecules.
USEFUL FOR

Students and researchers in physical chemistry, particularly those studying molecular spectroscopy and quantum mechanics, will benefit from this discussion.

bmarson123
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Homework Statement


The equilibrium separation of the atoms in H35CI equals 1.27 x 10-10m. Calculate the energy separation between adjacent lines in the rotational-vibrational spectrum


Homework Equations



E = (n + 1/2)[STRIKE]h[/STRIKE]\omega + [STRIKE]h[/STRIKE]2/ 2I * l(l+1)

I = \mur02 \mu = m1m2/ m1 + m2

The Attempt at a Solution



I am assuming the above equation for E is what I need to calculate to find the energy separation.

Using the above equation for inertia, I can find a value for it, meaning I can substitute it in.

I was wondering if it was possible for me to get rid of the n+1/2 and the l(l+1) parts from each bit if I assume n = 0 and l = 0?

\omega is obviously the angular momentum, but if I want to calculate that I either need to know the frequency or the force constant, but to calculate either of these, I need the energy. So I'm very confused with what to do!
 
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Think of the selection rules and find the energy of the absorbed
photons. You can assume that all molecules are in the vibrational ground state but the rotational levels are filled even a room temperature, so there can be transitions 1→2, 2→3, 3→4, and so on.

ehild
 

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