Dissection of Rovibronic Structure by Polarization-Resolved Two-Color Resonant Four-Wave Mixing Spectroscopy

Murdock, Daniel; Burns, Lori A.; Vaccaro, Patrick H.

doi:10.1021/jp903970d

Cited by 11 publications

(29 citation statements)

References 61 publications

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“…A detailed description of the TC-RFWM apparatus used in these investigations has been reported elsewhere, 47 consequently, only the most salient features will be presented here. Two moderate-resolution dye lasers (o0.15 cm À1 fundamental bandwidth which could be narrowed to o0.04 cm À1 by insertion of an intracavity etalon) were pumped by the second harmonics of separate injection-seeded Nd:YAG systems that were triggered externally to ensure temporal overlap of electromagnetic fields at the sample.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…To elucidate the influence of vibrational motion on large-amplitude hydron dynamics, the present work has implemented a fully coherent variant of the venerable stimulated emission pumping (SEP) technique 45 within the framework of two-color resonant four-wave mixing (TC-RFWM) spectroscopy. 46,47 This approach builds upon the basic paradigm of SEP, whereby two narrow-band sources of tunable laser light, commonly referred to as the PUMP and the DUMP, drive an inverted optical-optical double-resonance process designed to probe excited regions of the ground electronic manifold. For our TC-RFWM adaptation, a single PUMP field (i.e., having angular frequency o 1 and angular wavevector k 1 ) is fixed on a preselected rovibronic feature in the TrOH A ˜1B 48 This TC-RFWM scheme exhibits several unique characteristics, including laser-limited spectral resolution and true double-resonance response combined with high spatial, temporal, and polarization selectivity, which make it ideally suited for spectroscopic investigations of tropolone dynamics.…”

Section: Introductionmentioning

confidence: 99%

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Vibrational specificity of proton-transfer dynamics in ground-state tropolone

Murdock

Burns

Vaccaro

2010

Phys. Chem. Chem. Phys.

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The vibrational dependence of large-amplitude proton transfer taking place in the ground electronic state (X1A1) of tropolone has been explored by implementing a coherent variant of the stimulated emission pumping (SEP) technique within the framework of two-color resonant four-wave mixing (TC-RFWM) spectroscopy. The lowest 1700 cm(-1) portion of this potential surface has been interrogated under ambient bulk-gas conditions, enabling rotationless term energies (Tv+) and tunneling-induced bifurcations Delta(v)X to be extracted for 43 assigned vibrational features of a1 and b2 symmetry. The resulting values of Delta(v)X reflect the state-specificity long attributed to the hydron-migration pathways of tropolone and range in magnitude from 0.0 cm(-1) to 17.8 cm(-1), where the former implies essentially complete quenching of unimolecular dynamics whilst the latter represents nearly a twenty-fold increase in reaction rate over that of the zero-point level. This vibrational mediation of tunneling behavior is discussed in terms of attendant atomic displacements and permutation-inversion symmetries, with choreographed motion of the five-member reaction site (C-O-H...O=C) found to exert the most significant influence on the efficacy of proton transfer.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vibrational specificity of proton-transfer dynamics in ground-state tropolone

Murdock

Burns

Vaccaro

2010

Phys. Chem. Chem. Phys.

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“…Even though bright transitions might substantially broaden upon saturation, they are in general well separated from the “extra lines” that are made visible at increased laser powers. Furthermore, specific linear and circular polarisation configurations of the two resonant lasers allow further enhancement or discrimination of entire families of rovibronic transitions 25 for the characterisation of perturbation effects. Considering the quantum mechanical interference for perturbed levels involving perpendicular transitions, L -uncoupling is suggested for the system and consequently a 1 u symmetry label for the O 1 state.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic disentanglement of the quantum states of highly excited Cu2

et al. 2019

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Transition metals, characterised by their partially filled d orbitals, provide the basis for many of the most relevant processes in chemistry, biology, and physics. Embedded as single atoms or in small clusters, they give rise to exceptional optical, chemical, and magnetic properties. So far, it has proven impossible to disentangle the complex network of excited quantum states, which greatly hinders prediction and control of material properties. Here, we apply two-colour resonant four-wave mixing to quantitatively resolve the quantum states of the neutral copper dimer. This allows us to unwind the individual spectral lines by isotopic composition and rotational quantum number and reveals a rich network of bright and perturbing dark states. While this work presents a road map for the experimental study of the bonding between and with transition metal atoms, it also provides experimental reference data for prospective quantum chemical approaches on handling systems with a high density of states.

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“…Although many of these features are accompanied by modest CÀOÀH bending, one in particular, 16 ða 1 Þ, involves large-amplitude motion of both shuttling hydrons (dominantly H 1 ) perpendicular to the reaction coordinate. The latter can be correlated directly to the 15 ða 1 Þ mode of the bare TrOH substrate which markedly enhances the rate of single proton transfer [49]. The methine frequencies are predicted to be very stable upon complexation (retaining 99-108% of TrOH values), the lone exception being 17 ða 1 Þ, where an inflated TrOH fundamental arises from the coupling of carbon backbone deformations.…”

Section: Calculated Vibrational Frequenciesmentioning

confidence: 96%

Double proton transfer in the and states of the tropolone • HF complex

2010

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The ground (X 1 A 1 ) and first excited singlet (Ã 1 B 2 ) states of the binary tropolone Á HF complex have been examined computationally by exploiting minimal Hartree-Fock (HF/CIS), density functional (DFT/TDDFT), and coupled-cluster (CC/EOM-CC) schemes in conjunction with the aug-cc-pVDZ basis set. This adduct, formed by introducing a hydrogen fluoride ligand into the reaction cleft of the tropolone substrate, affords a model system for probing the nature of double proton-transfer events. Ab initio studies built upon the coupled-cluster ansatz predict a synchronous ground-state reaction barrier of DEX pt ¼ 1740:5 cm À1 height, which represents a 30% drop from the analogous quantity in bare tropolone. Redistribution of charge density upoñ A 1 B 2 ÀX 1 A 1 ( Ã ) electronic excitation transforms the potential energy landscape markedly, yielding a pronounced tightening of the critical O 1 ÀH Á Á Á FÀH Á Á Á O 2 interaction region (e.g., key heavy-atom distances decrease from rX O1ÁÁÁF ¼ 2:89 Å and rX O2ÁÁÁF ¼ 2:54 Å to rÃ O1ÁÁÁF ¼ 2:67 Å and rÃ O2ÁÁÁF ¼ 2:48 Å ) and a commensurate reduction in the impediment for hydron migration to DEÃ pt ¼ 1292:8 cm À1 . Intriguingly, the double proton transfer pathway inÃ 1 B 2 tropolone Á HF shows evidence of non-planarity, notably the presence of twisted transition-state (C 2 ) and global-minimum (C 1 ) configurations, that can be addressed within the framework of the encompassing G 4 molecular-symmetry group.

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Dissection of Rovibronic Structure by Polarization-Resolved Two-Color Resonant Four-Wave Mixing Spectroscopy

Cited by 11 publications

References 61 publications

Vibrational specificity of proton-transfer dynamics in ground-state tropolone

Vibrational specificity of proton-transfer dynamics in ground-state tropolone

Spectroscopic disentanglement of the quantum states of highly excited Cu2

Double proton transfer in the and states of the tropolone • HF complex

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