Herzberg–Teller approximation

E27647

spectroscopic approximation theoretical model in molecular spectroscopy

The Herzberg–Teller approximation is a refinement in molecular spectroscopy that accounts for vibronic coupling by allowing electronic transition dipole moments to depend on nuclear coordinates, explaining intensity in otherwise forbidden transitions.

Statements (46)

Predicate	Object
instanceOf	spectroscopic approximation → theoretical model in molecular spectroscopy →
addresses	breakdown of purely electronic selection rules → coupling between electronic and vibrational motion →
allows	non-zero intensity for electronically forbidden transitions → vibronically induced electronic transitions →
appliesTo	electronic absorption spectra of molecules → electronic emission spectra of molecules → vibronic spectra →
assumes	Born–Oppenheimer separation of electronic and nuclear motion as a starting point → electronic transition dipole moment depends on nuclear coordinates →
basedOn	expansion of transition dipole moment in normal coordinates →
category	molecular physics concept → quantum mechanical approximation → spectroscopy →
contrastsWith	Condon approximation →
describes	intensity borrowing in electronic transitions → intensity of vibronically allowed transitions → vibronic coupling →
enables	group-theoretical analysis of vibronically allowed transitions →
explains	intensity of symmetry-forbidden transitions → weak absorption bands in electronic spectra →
field	molecular quantum mechanics → molecular spectroscopy → quantum chemistry →
historicalContext	developed in mid-20th century molecular spectroscopy →
involves	breakdown of the Condon approximation → first-order dependence of transition dipole on vibrational coordinates →
mathematicalForm	Taylor expansion of transition moment around equilibrium geometry →
namedAfter	Edward Teller → Gerhard Herzberg →
refines	Franck–Condon approximation → Franck–Condon principle →
relatedTo	Born–Oppenheimer approximation → non-adiabatic coupling → vibronic coupling theory →
relevantFor	charge-transfer transitions → organic chromophores → polyatomic molecules → transition metal complexes →
usedFor	assignment of vibronic structure in spectra → simulation of absorption band shapes →
usedIn	analysis of vibronic progressions → calculation of transition intensities → computational spectroscopy → interpretation of molecular electronic spectra →

Referenced by (1)

Subject (surface form when different)	Predicate
Franck–Condon principle →	relatedTo