Two‐Photon Spectroscopy of Perturbed Benzenes

Goodman, Lionel; Rava, Richard P.

doi:10.1002/9780470142783.ch2

Cited by 18 publications

(2 citation statements)

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“…In the past, several theoretical models have been proposed to explain the vibronic intensity gain in the 2PA spectrum. Most have focused on symmetric (namely, centrosymmetric or quasi-centrosymmetric) molecules, where the electronically forbidden by symmetry 2PA transition becomes allowed due to the Herzberg–Teller (HT) coupling of an electronic transition dipole moment ( μ ) to a vibration with an appropriate symmetry. − In this situation, in the expansion of transition dipole moment into the Taylor series over the vibrational coordinate, the second term, containing the first derivative of μ over the coordinate becomes the dominant one, resultung in the shift of the whole vibronic progression to higher frequencies by a vibrational quantum. However, the FP chromophore has very low symmetry, so these models do not apply.…”

Section: Introductionmentioning

confidence: 99%

Describing Two-Photon Absorptivity of Fluorescent Proteins with a New Vibronic Coupling Mechanism

et al. 2012

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Fluorescent proteins (FPs) are widely used in two-photon microscopy as genetically-encoded probes. Understanding the physical basics of their two-photon absorption (2PA) properties is therefore crucial for creation of two-photon brighter mutants. On the other hand, it can give us better insight into molecular interactions of the FP chromophore with complex protein environment. It is known that, compared to one-photon absorption spectrum, where the pure electronic transition is the strongest, the 2PA spectrum of a number of FPs is dominated by a vibronic transition. The physical mechanism of such intensity redistribution is not understood. Here we present a new physical model that explains this effect through the “Herzberg-Teller”-type vibronic coupling of the difference between the permanent dipole moments in the ground and excited states (Δμ) to the bond-length-alternating coordinate. This model also enables us to quantitatively describe a large variability of the 2PA peak intensity in a series of red FPs with the same chromophore through the interference between the “Herzberg-Teller” and Franck-Condon terms.

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Section: Introductionmentioning

confidence: 99%

Describing Two-Photon Absorptivity of Fluorescent Proteins with a New Vibronic Coupling Mechanism

et al. 2012

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“…The basic expression for the transition probability is the same in two cases, and in as much as Raman tensor has proved to be immensely useful in chemistry for structural studies and for identification of symmetries of states, it is * For correspondence pertinent to explore the full potentiality of TPA in providing information on molecular states. Excellent reviews on TPA are given in Swofford and Albrecht (1978), Friedrich and McClain (1980) and Goodman and Rava (1983).…”

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confidence: 99%

One- and two-photon spectra of some selected molecules: A comparative study

Chowdhury

Chakraborty

Kundu

et al. 1991

Proc. Indian Acad. Sci. (Chem. Sci.)

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The complementarity of one-and two-photon spectroscopy has been utilised for throwing light on the following problems of chemical interest: (1) Weak interaction between identical chromophores separated by insulating bridges gives rise to split states of different symmetries. Two-photon spectroscopy (TPA), in conjunction with one-photon absorption (OPA), has been used to identify the states and hence to estimate the magnitude of interaction in bimolecules and trimolecules. From the shifts between the one-and the two-photon spectra, the splittings have been estimated. Calculations confirm that the dominant interaction is the through-bond one. (2) The second type of problem is the identification of g and u vibrations in molecules. We have initiated studies on three molecules in jet-cooled conditions: 9,10-dihydro-anthracene (DHA). 9,10-dihydro-phenanthrene (DHP) and octa-fluoronaphthalene (OFN). Only the one-photon fluorescence excitation spectra have so far been obtained by us and the TPA spectra are under investigation. (3) The third class of molecules discussed here are the Ln 3 + complexes where f"~ f" transitions are intrinsically two-photon allowed. We have studied two GD 3 + single crystals. The CF-splittings, observed clearly in TPA, have been fitted with a parametric model. Some of our observations on the variations of TPA intensity patterns from crystal to crystal, such as circular:linear polarisation ratios, relative intensities of transitions to different J-states, do not quite fit in with the Axe-Judd-Downer model. The discrepancies call for a reappraisal of the role of ligand in the TPA process.

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