Rotational and vibrational electric-dipole spectra
In an electric-dipole description, a pure rotational transition requires a molecular permanent dipole, while a normal-mode vibrational transition requires a changing dipole along that coordinate.
Key knowledge
In an electric-dipole description, a pure rotational transition requires a molecular permanent dipole, while a normal-mode vibrational transition requires a changing dipole along that coordinate. Thus a homonuclear diatomic has no ordinary pure electric-dipole rotational spectrum, even though it has rotational energy levels. Molecular symmetry and quantum matrix elements restrict allowed transitions.
Conditions and scope
- Electric-dipole restrictions do not exclude Raman, higher-multipole or collision-induced spectra.
- Actual intensities also depend on populations, transition strengths and experimental conditions.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read permanent-dipole and dipole-derivative criteria and molecular-symmetry context on pp.2–5; excluded categorical all-spectroscopy-is-dipole claim.
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Entry details
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- uni-chem-molecular-dipole-transitions
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- core.1
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- University core expansion