Resolved: Electronic states underneath broad absorptions

Cardoza, Job D.; Weber, Peter M.

doi:10.1063/1.2751189

Cited by 21 publications

(19 citation statements)

References 12 publications

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“…As we showed specifically on trimethylamine, the ionization from a Rydberg state to the associated state of the ion satisfies this condition 20. We have applied this idea to develop a molecular shape fingerprint spectroscopy,21 which has found useful applications in, among other areas, the identification of the charge center in a bifunctional molecule,22 the determination of chemical reaction pathways,23 and the observation of the conformeric dynamics in hot hydrocarbons 19.…”

Section: Introductionmentioning

confidence: 96%

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the Lowest Rydberg States of Trimethylamine

2008

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Resonance-enhanced multiphoton ionization photoelectron spectroscopy has been applied to study the electronic spectroscopy and relaxation pathways amongst the 3p and 3s Rydberg states of trimethylamine. The experiments used femtosecond and picosecond duration laser pulses at wavelengths of 416 nm, 266 nm, and 208 nm, and employed two-photon and three-photon ionization schemes. The binding energy of the 3s Rydberg state was found to be 3.087 ± 0.005 eV. The degenerate 3p x,y states have binding energies of 2.251 ± 0.005 eV, and 3p z is at 2.204 ± 0.005 eV. Using picosecond and femtosecond time-resolved experiments we spectrally and temporally resolved an intricate sequence of energy relaxation pathways leading from the 3p states to the 3s state. With excitation at 5.96 eV, trimethylamine is found to decay from the 3p z state to 3p x,y in 539 fs. The decay to 3s from all the 3p states takes place with a 2.9 ps time constant. On these time scales, trimethylamine does not fragment at the given internal energies, which range from 0.42 to 1.54 eV depending on the excitation wavelength and the electronic state.

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Section: Introductionmentioning

confidence: 96%

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the Lowest Rydberg States of Trimethylamine

2008

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“…The vibrational eigenfunctions do not change upon photoionization and most of the Franck-Condon envelope is enclosed in a narrow band. [12][13][14][15] Consequently, the spectra are largely insensitive toward internal vibrational energy. The sensitivity toward molecular structure coupled with the insensitivity toward vibrational excitation makes photoionization out of a Rydberg state an ideal tool to study ultrafast structural changes in large molecules.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast structural and isomerization dynamics in the Rydberg-exited Quadricyclane: Norbornadiene system

Rudakov

Weber

2012

The Journal of Chemical Physics

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The quadricyclane-norbornadiene system is an important model for the isomerization dynamics between highly strained molecules. In a breakthrough observation for a polyatomic molecular system of that complexity, we follow the photoionization from Rydberg states in the time-domain to derive a measure for the time-dependent structural dynamics and the time-evolving structural dispersion even while the molecule is crossing electronic surfaces. The photoexcitation to the 3s and 3p Rydberg states deposits significant amounts of energy into vibrational motions. We observe the formation and evolution of the vibrational wavepacket on the Rydberg surface and the internal conversion from the 3p Rydberg states to the 3s state. In that state, quadricyclane isomerizes to norbornadiene with a time constant of τ(2) = 136(45) fs. The lifetime of the 3p Rydberg state in quadricyclane is τ(1) = 320(31) and the lifetime of the 3s Rydberg state in norbornadiene is τ(3) = 394(32).

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“…[9] From the time sequence of the scattering patterns (Figure 2), we infer that the observed reaction is complete at 1ns. [9] From the time sequence of the scattering patterns (Figure 2), we infer that the observed reaction is complete at 1ns.…”

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confidence: 86%

“…In general, dissociation reactions can be difficult to study spectroscopically,s ince spectroscopic properties change between reactant and products. [9] At higher energy,reached by two-photon excitation with 400 nm, aslightly faster 3s internal conversion time constant of 2.0 ps was found. [8] Internal conversion leads to the 3p x and 3p y states with at ime constant of 540 AE 75 fs and then to the 3s state with atime constant of 2.9 AE 0.2 ps,asshown in Figure 1.…”

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confidence: 87%

“…[8] Internal conversion leads to the 3p x and 3p y states with at ime constant of 540 AE 75 fs and then to the 3s state with atime constant of 2.9 AE 0.2 ps,asshown in Figure 1. [9] At higher energy,reached by two-photon excitation with 400 nm, aslightly faster 3s internal conversion time constant of 2.0 ps was found. [8] Using time-of-flight photoionization with excitation at 193 nm, Forde et al [10,11] found three dissociative channels:adominant (72 AE 9%)channel involving asequential reaction to N-methylmethanimine (NMMA);aminor channel (27 AE 9%)r esulting in dimethylamine (DMA) and methyl radicals ejected with higher kinetic energy;a nd, possibly,at race amount of at hird channel involving as econdary dissociation of DMA resulting in NC 2 H 4 and molecular hydrogen with low kinetic energy.Inthe dominant pathway,the initially excited TMA first dissociates into DMA and CH 3 ,a nd then DMA fragments to form NMMA and hydrogen atoms.Because the experiments by Forde et al only identified the final reaction products,they could not measure the time scales of the kinetic steps nor confirm the electronic or geometrical structures of the DMA transients.T he intermediate reaction steps and the nature of the transient species therefore remain largely unknown.…”

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Simplicity Beneath Complexity: Counting Molecular Electrons Reveals Transients and Kinetics of Photodissociation Reactions

et al. 2019

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Time-resolved pump-probe gas-phase X-rays cattering signals,e xtrapolated to zero momentum transfer, provideameasure of the number of electrons in as ystem, an effect that arises from the coherent addition of elastic scattering from the electrons.T his allows to identify reactive transients and determine the chemical reaction kinetics without the need for extensive scattering simulations or complicated inversion of scattering data. We examine the photodissociation reaction of trimethylamine and identify two reaction paths upon excitation to the 3p state at 200 nm:afast dissociation path out of the 3p state to the dimethyl amine radical (16.6 AE 1.2 %) and aslower dissociation via internal conversion to the 3s state (83.4 AE 1.2 %). The time constants for the two reactions are 640 AE 130 fs and 74 AE 6ps, respectively.A dditionally,i ti sf ound that the transient dimethyl amine radical has aN ÀCb ond length of 1.45 AE 0.02 and aC ÀNÀCbond angle of 1188 8 AE 48 8.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Resolved: Electronic states underneath broad absorptions

Cited by 21 publications

References 12 publications

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the Lowest Rydberg States of Trimethylamine

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the Lowest Rydberg States of Trimethylamine

Ultrafast structural and isomerization dynamics in the Rydberg-exited Quadricyclane: Norbornadiene system

Simplicity Beneath Complexity: Counting Molecular Electrons Reveals Transients and Kinetics of Photodissociation Reactions

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