“…and agree with those obtained previously by analytical methods [12]. It should be noted that all the contributions to the above soRF come from the identity operator when the Green operator is simplified with the closure relation [10,16].…”
Section: Application To Cubic T ⊗ T Jt Systemssupporting
confidence: 90%
“…Since the JT systems considered here all involve the orbital triplet terms only, the Green operator can be simplified by writing it in terms of the ground electronic well state |ψ p using the closure relation as in [16]. However, the orbital operators after the introduction of the non-Condon correction do not satisfy the closure relation and thus G p (T 1 ) must be replaced by the standard form of second-order perturbation theory namely: (16) where E p m is the appropriate energy denominator including the non-Condon element. The general expression for the soRF within the corrected FC approximation thus becomes…”
Section: The Non-condon Perturbative Methodsmentioning
confidence: 99%
“…(2) p Mµ,corr ( l ⊗ m ) is now calculated with the corrected Green operator in equation (16). In this final result, we have terms independent of q p (which are the standard FC results) together with the non-Condon correction containing terms which are of order q 2 p .…”
Section: The Non-condon Perturbative Methodsmentioning
confidence: 99%
“…The FC approximation is an accurate analytical technique in the strong coupling regime. As emphasized in [10,16] for the octahedral T ⊗ t 2 and icosahedral T ⊗ h JT systems, respectively, the underlying physics is clearly exposed.…”
Section: The Franck-condon Approximation In the Theory Of Sorfs In Or...mentioning
It is well-known that vibronic interactions can be modelled in terms of an effective
Hamiltonian incorporating first and second-order reduction factors (RFs), particularly
when analysing the spectroscopic properties. Measurements and calculations of the RFs as
a function of the strength of vibronic coupling are therefore of much interest. In this paper,
we develop a new general method for determining second-order RFs (soRFs) from the
strength of the Jahn–Teller (JT) coupling for systems in which electron orbital degeneracy
or pseudo-degeneracy exists. These include in particular the fullerene molecule
C60, pseudo-Jahn–Teller molecules and impurity centres in crystals. In order to calculate the
important soRFs for intermediate to strong coupling, it is necessary to determine
non-Condon corrections to the strong coupling values obtained using the Franck–Condon
(FC) approximation. This gives an additional contribution to the nuclear polarizability of
the system, thus enabling the electrons to follow the nuclear vibrations. These non-Condon
corrections are derived using perturbation theory and are found to be inversely
proportional to the square of the JT energy. The validity of the approximation is first
tested in the cubic JT system due to its relative simplicity. It is found that the results are
closer to those obtained earlier by numerical methods than the analytical
FC values alone. Results are then presented that are applicable to
C60−
anions.
“…and agree with those obtained previously by analytical methods [12]. It should be noted that all the contributions to the above soRF come from the identity operator when the Green operator is simplified with the closure relation [10,16].…”
Section: Application To Cubic T ⊗ T Jt Systemssupporting
confidence: 90%
“…Since the JT systems considered here all involve the orbital triplet terms only, the Green operator can be simplified by writing it in terms of the ground electronic well state |ψ p using the closure relation as in [16]. However, the orbital operators after the introduction of the non-Condon correction do not satisfy the closure relation and thus G p (T 1 ) must be replaced by the standard form of second-order perturbation theory namely: (16) where E p m is the appropriate energy denominator including the non-Condon element. The general expression for the soRF within the corrected FC approximation thus becomes…”
Section: The Non-condon Perturbative Methodsmentioning
confidence: 99%
“…(2) p Mµ,corr ( l ⊗ m ) is now calculated with the corrected Green operator in equation (16). In this final result, we have terms independent of q p (which are the standard FC results) together with the non-Condon correction containing terms which are of order q 2 p .…”
Section: The Non-condon Perturbative Methodsmentioning
confidence: 99%
“…The FC approximation is an accurate analytical technique in the strong coupling regime. As emphasized in [10,16] for the octahedral T ⊗ t 2 and icosahedral T ⊗ h JT systems, respectively, the underlying physics is clearly exposed.…”
Section: The Franck-condon Approximation In the Theory Of Sorfs In Or...mentioning
It is well-known that vibronic interactions can be modelled in terms of an effective
Hamiltonian incorporating first and second-order reduction factors (RFs), particularly
when analysing the spectroscopic properties. Measurements and calculations of the RFs as
a function of the strength of vibronic coupling are therefore of much interest. In this paper,
we develop a new general method for determining second-order RFs (soRFs) from the
strength of the Jahn–Teller (JT) coupling for systems in which electron orbital degeneracy
or pseudo-degeneracy exists. These include in particular the fullerene molecule
C60, pseudo-Jahn–Teller molecules and impurity centres in crystals. In order to calculate the
important soRFs for intermediate to strong coupling, it is necessary to determine
non-Condon corrections to the strong coupling values obtained using the Franck–Condon
(FC) approximation. This gives an additional contribution to the nuclear polarizability of
the system, thus enabling the electrons to follow the nuclear vibrations. These non-Condon
corrections are derived using perturbation theory and are found to be inversely
proportional to the square of the JT energy. The validity of the approximation is first
tested in the cubic JT system due to its relative simplicity. It is found that the results are
closer to those obtained earlier by numerical methods than the analytical
FC values alone. Results are then presented that are applicable to
C60−
anions.
“…Thus the FC approximation is an accurate analytical technique in the strong coupling regime. As emphasized in [5] and [11] for the octahedral T ⊗ t 2 and icosahedral T ⊗ h JT systems respectively, the underlying physics of soRFs is clearly exposed by the FC analysis.…”
Section: Second-order Perturbation Theory Generates a Second-order Ha...mentioning
An effective Hamiltonian containing Jahn-Teller (JT) first-and secondorder vibronic reduction factors (RFs) is a convenient way of modelling the spectroscopic properties of solids and molecules in which vibronic interactions are important. It can act as a bridge between experimental data and basic theory. In particular, second-order RFs can give valuable information on many of the fundamental properties of strongly coupled systems. As interest in the icosahedral fullerene molecules and ions has grown over the last few years, it has become necessary to be able to calculate values for second-order RFs in icosahedral symmetry in terms of more fundamental vibronic coupling parameters. Following on from earlier work on the icosahedral T ⊗ h JT system, we present here results of such calculations of the second-order vibronic RFs for the icosahedral G ⊗ g, G ⊗ h, H ⊗ g and H ⊗ h JT systems. These systems are relevant for the ground and excited states of C 60 anions and cations. The calculations are based on the Franck-Condon approximation followed by additional non-Condon corrections. Previous work has demonstrated that such an approach can give values for the RFs close to those deduced from experiments.
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