The role of novel Rydberg-valence behaviour in the non-adiabatic dynamics of tertiary aliphatic amines

Thompson, Jason; Klein, Liv B.; Sølling, Theis I.; Paterson, Martin J.; Townsend, David

doi:10.1039/c5sc03616j

Cited by 36 publications

(60 citation statements)

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“…in o1 ps) and the other at B2.9 eV that has a delayed onset from zero pump-probe delay and subsequently decays on a very extended timescale. Based on several previous photoelectron studies of tertiary amine systems at comparable excitation wavelengths, 1,26,[28][29][30] the lower and higher binding energy peaks may be attributed to ionization from an initially prepared 3p state and the 3s state (populated subsequently via internal conversion), respectively.…”

Section: Resultsmentioning

confidence: 88%

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The effects of symmetry and rigidity on non-adiabatic dynamics in tertiary amines: a time-resolved photoelectron velocity-map imaging study of the cage-amine ABCO

Klein

Morsing

Livingstone

et al. 2016

Phys. Chem. Chem. Phys.

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The non-adiabatic relaxation dynamics of the tertiary cage-amine azabicyclo[2.2.2]octane (ABCO, also known as quinuclidine) have been investigated following 3p Rydberg excitation at 201 nm using femtosecond time-resolved photoelectron imaging (TRPEI). The aim of the study was to investigate the influence of the rigid and symmetric cage structure found in ABCO on the general non-adiabatic relaxation processes commonly seen in other tertiary aliphatic amines (TAAs). Our data is compared with TRPEI results very recently obtained for several structurally less rigid TAA systems [J. O. F. Thompson et al., Chem. Sci., 2016, 7, 1826-1839] and helps to confirm many of the previously reported findings. The experimental results for ABCO in the short-time (<1 ps) regime strongly support earlier conclusions suggesting that planarization about the N-atom is not a prerequisite for efficient 3p-3s internal conversion. Additionally, individual photoelectron peaks within our ABCO data show no temporal shifts in energy. As confirmed by our supporting quantum mechanical calculations, this demonstrates that neither internal conversion within the 3p manifold or significant conformational re-organization are possible in the ABCO system. This result therefore lends strong additional support to the active presence of such dynamical effects in other, less conformationally restricted TAA species, where photoelectron peak shifts are commonly observed. Finally, the extremely long (>1 ns) 3s Rydberg state lifetime seen in ABCO (relative to other TAA systems at similar excitation energies) serves to illustrate the large influence of symmetry and conformational rigidity on intramolecular vibrational redistribution processes previously implicated in mediating this aspect of the overall relaxation dynamics.

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Section: Resultsmentioning

confidence: 88%

“…The time-dependence of the photoelectron data was examined by undertaking a sequential global fit using a Levenberg-Marquardt routine, as previously used for the analysis of TRPEI data obtained for other TAA systems. 1,31 The 2D data S(E, Dt) are described using the following:…”

Section: Resultsmentioning

confidence: 99%

The effects of symmetry and rigidity on non-adiabatic dynamics in tertiary amines: a time-resolved photoelectron velocity-map imaging study of the cage-amine ABCO

Klein

Morsing

Livingstone

et al. 2016

Phys. Chem. Chem. Phys.

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“…Ther emaining 17 %o ft he molecules dissociate in the faster channel, with atime constant of 640 AE 130 fs.This can be seen by the kink in the curve of Figure 4, intercepted by the black dashed line,b efore the curve continues to decrease to À38.9 %a t1ns.T he 640 fs time constant is close to the previously observed 540 fs time constant for internal conversion within the 3p manifold, suggesting that both processes have ar elated dynamic origin that remains to be explored. [25,26] Here we observe that in traversing the conical intersection with other 3p states along this bond stretching coordinate,17% of the population dissociates while the rest undergoes internal conversion, as observed in the photoelectron spectra. 0scales as the square of the number of electrons of amolecule, ar esult of the coherent addition of scattering amplitudes.…”

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confidence: 51%

“…In previous studies of tertiary amines,i thas been noted that one of the 3p states is dissociative along the NÀCcoordinate. [25,26] Here we observe that in traversing the conical intersection with other 3p states along this bond stretching coordinate,17% of the population dissociates while the rest undergoes internal conversion, as observed in the photoelectron spectra. [11,12] This result also highlights that X-ray scattering provides ad irect measurement of populations in competing reaction channels without areliance on knowledge of photoionization cross-sections.…”

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confidence: 51%

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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“…Time-resolved photoelectron imaging (TRPEI) is a powerful variant of this general approach, yielding highly differential energy-and angle-resolved information that offers deep insight into the complex molecular photophysics. [8][9][10][11][12][13][14][15][16] A key requirement for time-resolved electronic spectroscopy is the generation of broadly tuneable UV femtosecond pulses. Commercial femtosecond laser systems, however, typically produce output centred in the near infrared (NIR).…”

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confidence: 99%

Ultrafast Molecular Spectroscopy Using a Hollow-Core Photonic Crystal Fiber Light Source

Kotsina

Belli

Gao

et al. 2019

J. Phys. Chem. Lett.

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We demonstrate, for the first time, the application of rare-gas filled hollow-core photonic crystal fibres (HC-PCFs) as tuneable ultraviolet light sources in femtosecond pump-probe spectroscopy. The time-resolved photoelectron imaging technique reveals non-adiabatic dynamical processes operating on three distinct timescales in the styrene molecule following excitation over the 242-258 nm region. These include ultrafast (<100 fs) internal conversion between the S2(ππ*) and S1(ππ*) electronic states and subsequent intramolecular vibrational energy redistribution within S1(ππ*). Compact, cost-effective and highly efficient bench-top HC-PCF sources have huge potential to open up many exciting new avenues for ultrafast spectroscopy in the ultraviolet and vacuum ultraviolet spectral regions. We anticipate that our initial validation of this approach will generate important impetus in this area. a Corresponding author: d.townsend@hw.ac.uk

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The role of novel Rydberg-valence behaviour in the non-adiabatic dynamics of tertiary aliphatic amines

Abstract: Time-resolved photoelectron imaging was used to study non-adiabatic relaxation dynamics in N,N-dimethylisopropylamine, N,N-dimethylpropylamine and N-methylpyrrolidine following excitation at 200 nm.

Cited by 36 publications

References 60 publications

The effects of symmetry and rigidity on non-adiabatic dynamics in tertiary amines: a time-resolved photoelectron velocity-map imaging study of the cage-amine ABCO

The effects of symmetry and rigidity on non-adiabatic dynamics in tertiary amines: a time-resolved photoelectron velocity-map imaging study of the cage-amine ABCO

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

Ultrafast Molecular Spectroscopy Using a Hollow-Core Photonic Crystal Fiber Light Source

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