Two-photon spectroscopy of Rydberg states of jet-cooled C2H4 and C2D4

Williams, Bradley A.; Cool, Terrill A.

doi:10.1063/1.460314

Cited by 88 publications

(69 citation statements)

References 46 publications

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“…However, the quantitative agreement between the experimentally determined time constants and the corresponding parameters extracted from the spectrum generated from high level ab initio dynamics engender confidence in the present assignment. The main products observed in previous studies of the gas-phase photolysis, C 2 H 4 + CH 2 , have ionization energies of 10.40 eV 47 and 10.51 eV, 48 respectively, and would thus require ionization with 3 probe photons from their ground state. For the low probe laser intensities used in the current experiments, such channels were not observed.…”

Section: Discussionmentioning

confidence: 99%

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics

Coates

Larsen

Forbes

et al. 2018

The Journal of Chemical Physics

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The vacuum-ultraviolet photoinduced dynamics of cyclopropane (C 3 H 6) were studied using timeresolved photoelectron spectroscopy (TRPES) in conjunction with ab initio quantum dynamics simulations. Following excitation at 160.8 nm, and subsequent probing via photoionization at 266.45 nm, the initially prepared wave packet is found to exhibit a fast decay (<100 fs) that is attributed to the rapid dissociation of C 3 H 6 to ethylene (C 2 H 4) and methylene (CH 2). The photodissociation process proceeds via concerted ring opening and CC bond cleavage in the excited state. Ab initio multiple spawning simulations indicate that ring-opening occurs prior to dissociation. The dynamics simulations were subsequently employed to simulate a TRPES spectrum, which was found to be in excellent agreement with the experimental result. On the basis of this agreement, the fitted time constants of 35 ± 20 and 57 ± 35 fs were assigned to prompt (i) dissociation on the lowest-lying excited state, prepared directly by the pump pulse, and (ii) non-adiabatic relaxation from higher-lying excited states that lead to delayed dissociation, respectively.

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Section: Discussionmentioning

confidence: 99%

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics

Coates

Larsen

Forbes

et al. 2018

The Journal of Chemical Physics

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“…Additional assignments have been made in later work. [49][50][51][52] A large number of references to prior theoretical work are given by Lindh and Roos. 53 The major feature of the spectrum is the broad band with a maximum at 7.66 eV, which arises from the →* transition ͑also known as the N→V transition or, in terms of electronic states, the 1 1 A g →1 1 B 1u transition͒.…”

Section: A Ethylenementioning

confidence: 99%

Coupled-cluster calculations of the excitation energies of ethylene, butadiene, and cyclopentadiene

Watts

Gwaltney

Bartlett

1996

The Journal of Chemical Physics

151

127

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The equation-of-motion coupled-cluster ͑EOM-CC͒ method has been used to calculate the vertical excitation energies of ethylene, trans-butadiene, cis-butadiene, and cyclopentadiene. The approximations used were the EOM-CC singles-and-doubles ͑EOM-CCSD͒ method and EOM-CCSD with a noniterative treatment of triple excitations, EOM-CCSD͑T͒, EOM-CCSD͑T͒. The basis sets were atomic natural orbital sets augmented with diffuse functions. Comparisons have been made with a series of complete active space second-order perturbation theory ͑CASPT2͒ results, which used the same basis sets and geometries, and experiment. For the Rydberg states the EOM-CCSD results were in good agreement with experiment and CASPT2. The results for the valence states show more variation. For ethylene CASPT2 exaggerates the Rydberg character of the V state, while EOM-CCSD provides a better description. For the valence states of the other molecules the EOM-CCSD excitation energies tend to be too high, but considerable improvements are given by EOM-CCSD͑T͒. For the 1 1 B u /1 1 B 2 states of butadiene and cyclopentadiene EOM-CCSD͑T͒ agrees well with experiment and CASPT2. The agreement for the 1 1 A g →2 1 A g and 1 1 A 1 →2 1 A 1 transitions for trans-butadiene and cis-butadiene, which are not known experimentally, is not so good, with the EOM-CC results significantly higher than the CASPT2 ones. However, the EOM-CCSD͑T͒ and CASPT2 energies for the 1 1 A 1 →2 1 A 1 transition in cyclopentadiene are in quite close agreement and both agree well with experiment. EOM-CCSD͑T͒ shows an average error in vertical excitation energies for all states of all molecules of 0.12 eV, and improves those for valence states from an error of 0.26 eV for EOM-CCSD to 0.13 eV.

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“…(1) The species ionization energy is 410.5 eV, as in the case of CH 4 (12.6 eV 52 ), C 2 H 4 (10.51 eV 53 ) and C 2 H 6 (11.5 eV 54 ).…”

Section: Modelling Of Flash Photolysis With Mbmsmentioning

confidence: 99%

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Buras

Chu

Jamal

et al. 2018

Phys. Chem. Chem. Phys.

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The C9H11 potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C9H11 PES has already been extensively studied both experimentally (under single-collision and thermal conditions) and theoretically, new insights were made in this work by taking a new experimental approach: flash photolysis combined with time-resolved molecular beam mass spectrometry (MBMS) and visible laser absorbance. The C9H11 PES was experimentally accessed by photolytic generation of the phenyl radical and subsequent reaction with excess propene (C6H5 + C3H6). The overall kinetics of C6H5 + C3H6 was measured using laser absorbance with high time-resolution from 300 to 700 K and was found to be in agreement with earlier measurements over a lower temperature range. Five major product channels of C6H5 + C3H6 were observed with MBMS at 600 and 700 K, four of which were expected: hydrogen (H)-abstraction (measured by the stable benzene, C6H6, product), methyl radical (CH3)-loss (styrene detected), H-loss (phenylpropene isomers detected) and radical adduct stabilization. The fifth, unexpected product observed was the benzyl radical, which was rationalized by the inclusion of a previously unreported pathway on the C9H11 PES: aromatic-catalysed 1,2-H-migration and subsequent resonance stabilized radical (RSR, benzyl radical in this case) formation. The current theoretical understanding of the C9H11 PES was supported (including the aromatic-catalyzed pathway) by quantitative comparisons between modelled and experimental MBMS results. At 700 K, the branching to styrene + CH3 was 2-4 times greater than that of any other product channel, while benzyl radical + C2H4 from the aromatic-catalyzed pathway accounted for ∼10% of the branching. Single-collision conditions were also simulated on the updated PES to explain why previous crossed molecular beam experiments did not see evidence of the aromatic-catalyzed pathway. This experimentally validated knowledge of the C9H11 PES was added to the database of the open-source Reaction Mechanism Generator (RMG), which was then used to generalize the findings on the C9H11 PES to a slightly more complicated alkylaromatic system.

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Two-photon spectroscopy of Rydberg states of jet-cooled C2H4 and C2D4

Abstract: Resonant two-photon ionization spectroscopy of jet-cooled tantalum carbide, TaC

Cited by 88 publications

References 46 publications

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics

Coupled-cluster calculations of the excitation energies of ethylene, butadiene, and cyclopentadiene

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

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