The differences in zero-point energy between isotopes

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Discussion Overview

The discussion centers on the differences in zero-point energy between the isotopes H2 and D2, specifically focusing on their vibrational energy at ground state, maximum vibrational quantum number, and equilibrium vibrational energy. The scope includes theoretical considerations of vibrational frequencies and quantum mechanics.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires about which isotope, H2 or D2, has higher vibrational energy at ground state and why.
  • Another participant explains that zero-point energy is proportional to the frequency of oscillation, which is influenced by the mass of the isotopes, suggesting that D2 will have a lower oscillation frequency due to its larger mass.
  • A participant questions the relationship between maximum vibrational quantum number and equilibrium vibrational energy, suggesting that since maximum vibrational quantum number does not depend on mass, it should remain unchanged.
  • There is a suggestion that equilibrium vibrational energy should be affected by oscillation frequency, which is mass-dependent.

Areas of Agreement / Disagreement

Participants express differing views on the implications of mass on maximum vibrational quantum number and equilibrium vibrational energy, indicating that the discussion remains unresolved regarding these relationships.

Contextual Notes

Participants have not reached a consensus on how mass influences maximum vibrational quantum number and equilibrium vibrational energy, and there are unresolved assumptions regarding the relationships between these quantities.

Chaste
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Hi all,

May I know which would have a higher vibrational energy at ground state, zero point energy, maximum vibrational quantum number, between the these 2 isotopes: H2 and D2

and why?
 
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The zero point energy is proportionate to the frequency of oscillation, and in the typical model system of masses connected by a spring, the oscillation frequency goes as \sqrt{k/m}. The spring constant k is determined by the chemistry and will be unaffected by the nuclear masses. So D<sub>2</sub> will have a lower oscillation frequency due to the larger mass.
 
kanato said:
The zero point energy is proportionate to the frequency of oscillation, and in the typical model system of masses connected by a spring, the oscillation frequency goes as \sqrt{k/m}. The spring constant k is determined by the chemistry and will be unaffected by the nuclear masses. So D<sub>2</sub> will have a lower oscillation frequency due to the larger mass.

thanks.
so what about it's maximum vibrational quantum number and it's equilibrium vibrational energy? are they the same? but thinking about ur statement, there's no mass to consider when relating to vmax and veq. so there shd be no change as well?
 
Chaste said:
thanks.
so what about it's maximum vibrational quantum number and it's equilibrium vibrational energy? are they the same? but thinking about ur statement, there's no mass to consider when relating to vmax . so there shd be no change as well?

and for veq it should be affected as it's related to the oscillation frequency as well.
 

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