Bond-Selected Chemistry:  Vibrational State Control of Photodissociation and Bimolecular Reaction

Crim, F. Fleming

doi:10.1021/jp9604812

Cited by 353 publications

(240 citation statements)

References 68 publications

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“…Table I clearly shows that the more strongly interacting solvents accelerate the intramolecular relaxation at all excitation levels but does not indicate the IVR times in the absence of solvent. The 2 s overtone relaxation measurements 61 in supercritical CO 2 give a relaxation time of 15 ps that is comparable to our measurement of 12 ps in CCl 4 , the most weakly interacting solvent studied. This similarity suggests that the intramolecular energy transfer time of isolated CH 2 I 2 may not be very different, but measurements in the gas phase are necessary to completely separate the solvent environment from the IVR process.…”

Section: Solvent Dependencesupporting

confidence: 84%

“…Since nuclear motion transforms reactants into products, the rate, and even the outcome, of a reaction depends on the amount and distribution of vibrational energy. 1,2 The vibrational dynamics are therefore ultimately responsible for the evolution of a reactive system, and the processes that move energy within and out of a molecule play an essential role. Short-pulse lasers can directly follow this flow of energy by exciting a specific vibrational motion and monitoring the transient response of the molecule, [3][4][5] providing a test for theoretical treatments of vibrational energy transfer.…”

Section: Introductionmentioning

confidence: 99%

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Vibrational relaxation of CH2I2 in solution: Excitation level dependence

Elles

Bingemann

Heckscher

et al. 2003

The Journal of Chemical Physics

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Transient electronic absorption monitors the flow of vibrational energy in methylene iodide (CH 2 I 2 ) following excitation of five C-H stretch and stretch-bend modes ranging in energy from 3000 to 9000 cm Ϫ1 . Intramolecular vibrational relaxation ͑IVR͒ occurs through a mechanism that is predominantly state-specific at the C-H stretch fundamental but closer to the statistical limit at higher excitation levels. The IVR times change with the excitation energy between the fundamental and first C-H stretch overtone but are constant above the overtone. The intermolecular energy transfer ͑IET͒ times depend only weakly on the initial excitation level. Both the IVR and the IET times depend on the solvent ͓CCl 4 , CDCl 3 , C 6 D 6 , C 6 H 6 , or (CD 3 ) 2 CO] and its interaction strength, yet there is no energy level dependence of the solvent influence.

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Section: Solvent Dependencesupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Vibrational relaxation of CH2I2 in solution: Excitation level dependence

Elles

Bingemann

Heckscher

et al. 2003

The Journal of Chemical Physics

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“…It is well-known that the vibrational quantum state on a reactant surface can severely influence the ensuing excited state dynamics. [30][31][32][33][34] Indeed, we find in our ultrafast experiments that the CSSs are formed on two distinct timescales representing ET from a hot 3 MLCT ( 3 MLCT*) ( hot = 3.6 ps) and a relaxed 3 MLCT ( cool = 14.7 ps). Note however that we do not find any evidence of (C C) v>0 population in the TRIR data beyond the instrument-limited time resolution of ca.…”

Section: Excited State Dynamics Without Ir Excitationmentioning

confidence: 99%

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

et al. 2017

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Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer Donor-Bridge-Acceptor-Bridge-Donor "fork" system: asymmetric 13 C isotopic labelling of one of the two -C≡C-bridges makes the two parallel and otherwise identical Donor→Acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV pump (excitation)-IR pump (perturbation)-IR probe (monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron-transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices. Main TextControlling the function of future advanced materials demands a profound understanding of energymatter interactions in molecular systems at the quantum level. 1 There is a growing consensus that energy-and electron-transfer processes occurring far away from equilibrium in condensed-phase systems on femto-to-picosecond timescales do not conform to the Born-Oppenheimer approximation. Indeed, nuclear and electronic wave functions often strongly interact with each other, leading to exotic phenomena whereby vibrational motion can mediate and dictate the rate and efficiency of electronic transitions. [2][3][4][5] With overwhelming evidence that nuclear-electronic (vibronic) interactions play a crucial role in a broad range of systems, including light harvesting and conversion in photosynthetic organisms, 6-11 this phenomenon represents a tremendous opportunity to acquire deeper knowledge and control over the structural traits that govern molecular function and reactivity.Recent efforts led by Rubtsov et al.,12,13 Bakulin et al., 14 and our group 15,16 have shown that one way to experimentally exploit vibronic coupling to modulate molecular function is to introduce targeted vibrational excitation along specific reaction co-ordinates using ultrafast mid-infrared (IR) pulses. This approach enables promoting or suppressing electronic transitions, notably photo-induced electron transfer (ET), an elementary process that pervades the natural world. Although the demonstrated excited state modulations have been remarkably efficient, up to 100% suppression in one case, 15 predictive and directive control of electron transfer in the condensed phase has not been achieved yet.

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“…[1][2][3] Photons are directed to a selected chemical bond in a molecule to achieve a highefficiency energy coupling into a physical or chemical process. The purpose of the resonant excitation is to realize selective bond breaking and control reaction pathways.…”

Section: Introductionmentioning

confidence: 99%

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

Líu

Xie

Gao

et al. 2009

Journal of Applied Physics

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Wavelength-matched vibrational excitations of ethylene ͑C 2 H 4 ͒ molecules using a tunable carbon dioxide ͑CO 2 ͒ laser were employed to significantly enhance the chemical vapor deposition ͑CVD͒ of diamond in open air using a precursor gas mixture of C 2 H 4 , acetylene ͑C 2 H 2 ͒, and oxygen ͑O 2 ͒. The CH 2 -wag vibration mode ͑ 7 ͒ of the C 2 H 4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 m were applied to the CVD processes to compare the C 2 H 4 excitations and diamond depositions. Compared with 10.591 m produced by common CO 2 lasers, the laser wavelength of 10.532 m is much more effective to excite the C 2 H 4 molecules through the CH 2 -wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 m, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced.

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Bond-Selected Chemistry: Vibrational State Control of Photodissociation and Bimolecular Reaction

Cited by 353 publications

References 68 publications

Vibrational relaxation of CH2I2 in solution: Excitation level dependence

Vibrational relaxation of CH2I2 in solution: Excitation level dependence

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

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