Nuclear Motions Associated with Electron Transitions in Diatomic Molecules

Condon, E. U.

doi:10.1103/physrev.32.858

Cited by 807 publications

(388 citation statements)

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“…Such localization leads to an appearance of a significant transition dipole moment (and oscillator strength, see Table 1) during excited state equilibration (S 1 → S 1′ ). This strongly violates the commonly used Condon approximation 38 stating that the dipole should be independent of the vibrational coordinates. Such excited state vibronic processes thus make large CPPs to be excellent fluorescent chromophores with quantum yields well exceeding 50% as observed in many experiments ( Table 1).…”

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confidence: 69%

Self-Trapping of Excitons, Violation of Condon Approximation, and Efficient Fluorescence in Conjugated Cycloparaphenylenes

et al. 2014

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Cycloparaphenylenes, the simplest structural unit of armchair carbon nanotubes, have unique optoelectronic properties counterintuitive in the class of conjugated organic materials. Our time-dependent density functional theory study and excited state dynamics simulations of cycloparaphenylene chromophores provide a simple and conceptually appealing physical picture explaining experimentally observed trends in optical properties in this family of molecules. Fully delocalized degenerate second and third excitonic states define linear absorption spectra. Self-trapping of the lowest excitonic state due to electron−phonon coupling leads to the formation of spatially localized excitation in large cycloparaphenylenes within 100 fs. This invalidates the commonly used Condon approximation and breaks optical selection rules, making these materials superior fluorophores. This process does not occur in the small molecules, which remain inefficient emitters. A complex interplay of symmetry, π-conjugation, conformational distortion and bending strain controls all photophysics of cycloparaphenylenes.

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confidence: 69%

Self-Trapping of Excitons, Violation of Condon Approximation, and Efficient Fluorescence in Conjugated Cycloparaphenylenes

et al. 2014

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“…[17][18][19][20] Even though the additional assignments in the first four bands have been debated in literature, Gouterman and Edwards made a key observation in 1970. They noted that the Q band, in particular, would be subject to Franck-Condon (FC) [21][22][23] vibrational displacement, and point to an earlier publication by Gouterman and Fulton, in which the higher energy bands were believed to take on much more peculiar shapes, especially at the investigated temperature of 0 K. 24 Some believe the four orbital model is simplistic, but the framework is generally still reliable for the major transitions, and is used in this present work. Most functionals used for time-dependent density functional theory (TDDFT) have not been extremely accurate, leading to low energy excitations that are usually blue shifted.…”

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confidence: 99%

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Theisen

Huang

Fleetham

et al. 2015

The Journal of Chemical Physics

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Articles you may be interested inGround and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis The electronic structure of eight zinc-centered porphyrin macrocyclic molecules are investigated using density functional theory for ground-state properties, time-dependent density functional theory (TDDFT) for excited states, and Franck-Condon (FC) analysis for further characterization of the UV-vis spectrum. Symmetry breaking was utilized to find the lowest energy of the excited states for many states in the spectra. To confirm the theoretical modeling, the spectroscopic result from zinc phthalocyanine (ZnPc) is used to compare to the TDDFT and FC result. After confirmation of the modeling, five more planar molecules are investigated: zinc tetrabenzoporphyrin (ZnTBP), zinc tetrabenzomonoazaporphyrin (ZnTBMAP), zinc tetrabenzocisdiazaporphyrin (ZnTBcisDAP), zinc tetrabenzotransdiazaporphyrin (ZnTBtransDAP), and zinc tetrabenzotriazaporphyrin (ZnTBTrAP). The two latter molecules are then compared to their phenylated sister molecules: zinc monophenyltetrabenzotriazaporphyrin (ZnMPTBTrAP) and zinc diphenyltetrabenzotransdiazaporphyrin (ZnDPTBtransDAP). The spectroscopic results from the synthesis of ZnMPTBTrAP and ZnDPTBtransDAP are then compared to their theoretical models and nonphenylated pairs. While the Franck-Condon results were not as illuminating for every B-band, the Q-band results were successful in all eight molecules, with a considerable amount of spectral analysis in the range of interest between 300 and 750 nm. The π-π * transitions are evident in the results for all of the Q bands, while satellite vibrations are also visible in the spectra. In particular, this investigation finds that, while ZnPc has a D 4h symmetry at ground state, a C 4v symmetry is predicted in the excited-state Q band region. The theoretical results for ZnPc found an excitation energy at the Q-band 0-0 transition of 1.88 eV in vacuum, which is in remarkable agreement with published gas-phase spectroscopy, as well as our own results of ZnPc in solution with Tetrahydrofuran that are provided in this paper. C 2015 AIP Publishing LLC. [http://dx

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“…The large calculated value of f (−2,−5) = 0.8(1) is surprising at first glance, since the wave function of v ′ = −5 shows 38 oscillations, while the wave function of v = −2 shows 61. However, according to the Franck-Condon principle [29], molecular transitions most readily occur between rovibrational levels of two different electronic states with nearly the same classical turning points. In the adiabatic picture the classical turning points of v ′ = −5 and v = −2 are very close, with their respective inner points at 7.1 and 7.5a 0 and outer points at 47.1 and 50.0a 0 .…”

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Optical Production of Stable UltracoldSr288Molecules

et al. 2012

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We have produced large samples of stable ultracold 88 Sr2 molecules in the electronic ground state in an optical lattice. The fast, all-optical method of molecule creation involves a nearintercombination-line photoassociation pulse followed by spontaneous emission with a near-unity Franck-Condon factor. The detection uses excitation to a weakly bound electronically excited vibrational level corresponding to a very large dimer and yields a high-Q molecular vibronic resonance. This is the first of two steps needed to create deeply bound 88 Sr2 for frequency metrology and ultracold chemistry.PACS numbers: 67.85. 34.50.Rk, 37.10.Jk, 37.10.Pq The rapid progress in laser cooling has given rise to many new fields of research. One important example is the study of ultracold, dense clouds of molecules. The molecules can exhibit new physical phenomena near quantum degeneracy [1][2][3]. For example, long-range anisotropic interactions are expected between heteronuclear polar molecules. Such molecules have also been explored as a paradigm for quantum information and computation [4]. On the other hand, homonuclear molecular dimers without a dipole moment present a metrological interest, for example in constraining the variation of the electron-proton mass ratio [5,6] or complementing atomic clocks by serving as time standards in the terahertz regime [6]. These molecules also provide an excellent testing ground for many possible approaches to creating large ultracold samples, trapping them to allow long interrogation times, and precisely controlling their quantum states. The four promising routes toward trapped neutral molecules [1] are direct control of polar molecule dynamics via electric fields; buffer gas cooling of magnetic species; direct laser cooling of a suitable class of molecules [7]; and using magnetic or optical fields to combine laser cooled atoms into dimers [8][9][10][11][12]. The latter process typically results in molecules with relatively small binding energies but nonetheless has played a major role in the study of new phenomena. These dimers are also most promising for quantum control, since they are routinely produced at sub-µK temperatures.In this Letter, we describe optical production of 88 Sr 2 in the electronic ground state in an optical lattice. In contrast to alkali-metal atoms, Sr atoms possess no electronic spin and cannot be combined into molecules via the magnetic Feshbach resonance technique [13]. However, Sr has the advantage of the intercombination (spinforbidden) transition from the ground state, 1 S 0 − 3 P 1 (7 kHz linewidth [14], 689 nm wavelength), which allows Doppler cooling to < 1 µK [15] and provides several features that enable efficient photoassociation (PA) into molecules [14,16]. The unusually fast time scale (0.25 s) of ultracold molecule production is particularly important for establishing a short duty cycle in metrological applications. Furthermore, there is active interest in exploring molecules of alkaline-earth-metal (and the isoelectronic Yb) atoms in various combina...

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Nuclear Motions Associated with Electron Transitions in Diatomic Molecules

Cited by 807 publications

References 21 publications

Self-Trapping of Excitons, Violation of Condon Approximation, and Efficient Fluorescence in Conjugated Cycloparaphenylenes

Self-Trapping of Excitons, Violation of Condon Approximation, and Efficient Fluorescence in Conjugated Cycloparaphenylenes

Ground and excited states of zinc phthalocyanine, zinc tetrabenzoporphyrin, and azaporphyrin analogs using DFT and TDDFT with Franck-Condon analysis

Optical Production of Stable UltracoldSr288Molecules

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