Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical

Röder, Anja; Humeniuk, Alexander; Giegerich, Jens; Fischer, Ingo; Poisson, L.; Mitrić, Roland

doi:10.1039/c7cp01437f

Cited by 10 publications

(25 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…23,46,47 Although originally assigned to a ππ* excitation, the D 3 state was recently reassigned to a C 2 A 1 3s Rydberg state. 22 In benzyl, a correct assignment required multi-reference configuration interaction (MRCI) calculations with a large basis set; an approach that is beyond our means in the present work. We therefore assume that the description obtained for benzyl also holds for both xylyl isomers.…”

Section: Rempi-and H-atom Action Spectramentioning

confidence: 99%

“…[18][19][20] The nonradiative deactivation after UV excitation was studied by time-resolved spectroscopy and a fast deactivation of the UV excited states through conical intersections was identified. [21][22][23] In contrast, work on the three xylyl radical isomers has been limited so far. Only the D 1 ← D 0 transition (A 2 A 2 ← X 2 B 2 in C 2v symmetry) has been studied by laser induced fluorescence.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Photodissociation dynamics of the ortho- and para-xylyl radicals

Pachner

Steglich

Hemberger

et al. 2017

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

The photodissociation dynamics of the CH isomers ortho- and para-xylyl are investigated in a free jet. The xylyl radicals are generated by flash pyrolysis from 2-(2-methylphenyl)- and 2-(4-methylphenyl) ethyl nitrite and are excited into the D state. REMPI- spectra show vibronic structure and the origin of the transition is identified at 32 291 cm for the para- and at 32 132 cm for the ortho-isomer. Photofragment H-atom action spectra show bands at the same energy and thus confirm H-atom loss from xylyl radicals. To gain further insight into the photodissociation dynamics, velocity map images of the hydrogen atom photofragments are recorded. Their angular distribution is isotropic and the translational energy release is in agreement with a dissociation to products in their electronic ground state. Photodissociation of para-xylyl leads to the formation of para-xylylene (CH), while the data for ortho-xylyl agree much better with the isomer benzocyclobutene as the dominant molecular fragment rather than ortho-xylylene. In computations we identified a new pathway for the reaction ortho-xylyl → benzocyclobutene + H with a barrier of 3.39 eV (27 340 cm), which becomes accessible at the employed excitation energy. It proceeds via a combination of scissoring and rotational motion of the -CH and -CH groups. However, the observed rate constants measured by delaying the excitation and ionization laser with respect to each other are significantly faster than computed ones, indicating intrinsic non-RRKM behaviour. A comparably high value of around 30% of the excess energy is released as translation of the H-atom photofragment.

show abstract

Section: Rempi-and H-atom Action Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photodissociation dynamics of the ortho- and para-xylyl radicals

Pachner

Steglich

Hemberger

et al. 2017

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Strong fluorescence has been observed between 400-600 nm and attributed to the lowest excited A 2 B2-state [143][144][145][146][147] , which couples strongly to the nearly isoenergetic B 2 A2-state 148 , whose symmetries have been reassigned recently 120 . These two states have been confirmed by various theoretical approaches to be of valence * character 120,149,150 . The next higher C state lies at 4.06 eV 151 152 and was recently reassigned to a Rydberg-type 2 A1 (3s) state 120 .…”

Section: Electronic Structurementioning

confidence: 99%

“…With To attribute this change to specific excited states of the benzyl radical, we simulated the nonadiabatic relaxation dynamics employing the surface hopping approach outlined in the Computational section. According to ab initio calculations employing the complete active space self-consistent field method (CASSCF) combined with multireference configuration interaction (MRCI) 120 , 3p…”

Section: Relaxation Dynamicsmentioning

confidence: 99%

“…Our work on the benzyl radical shows beautifully how different probe wavelengths illuminate different timescales, but they also illustrate how involved and non-"black-box" the description of its excited states are: in the benzyl case TDDFT descriptions of the excited states consistently failed to reproduce the energetic ordering of the Rydberg states relative to the *-states (cf. Supplementary Material to Ref 120. ), showing that the electronic method has to be chosen with care.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals, and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations

et al. 2019

Self Cite

View full text Add to dashboard Cite

Reactive hydrocarbon molecules like radicals, biradicals and carbenes are not only key players in combustion processes and interstellar and atmospheric chemistry, but some of them are also important intermediates in organic synthesis. These systems typically possess many low-lying, strongly coupled electronic states. After light absorption, this leads to rich photodynamics characterized by a complex interplay of nuclear and electronic motion, which is still not comprehensively understood and not easy to investigate both experimentally and theoretically. In order to elucidate trends and contribute to a more general understanding, we here review our recent work on excitedstate dynamics of open-shell hydrocarbon species using time-resolved photoelectron spectroscopy and field-induced surface hopping simulations, and report new results on the excited-state dynamics of the tropyl and the 1-methylallyl radical. The different dynamics are compared, and the difficulties and future directions of time-resolved photoelectron spectroscopy and excited state dynamics simulations of open-shell hydrocarbon molecules are discussed.

show abstract

Dimerization of the Benzyl Radical in a High‐Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy

Hirsch

Constantinidis

Fischer

et al. 2018

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

We investigate the self-reaction of benzyl, C H , in a high-temperature pyrolysis reactor. The work is motivated by the observation that resonance-stabilized benzyl radicals can accumulate in reactive environments and contribute to the formation of polycyclic aromatic hydrocarbons (PAHs) and soot. Reaction products are detected by IR/UV ion dip spectroscopy, using infrared radiation from the free electron laser FELIX, and are identified by comparison with computed spectra. Among the reaction products identified by their IR absorption are several PAHs linked to toluene combustion such as bibenzyl, phenanthrene, diphenylmethane, and fluorene. The identification of 9,10-dihydrophenanthrene provides evidence for a mechanism of phenanthrene formation from bibenzyl that proceeds by initial cyclization rather than an initial hydrogen loss to stilbene.

show abstract

Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical

Abstract: We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C7H7, after UV excitation.

Cited by 10 publications

References 61 publications

Photodissociation dynamics of the ortho- and para-xylyl radicals

Photodissociation dynamics of the ortho- and para-xylyl radicals

Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals, and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations

Dimerization of the Benzyl Radical in a High‐Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy

Contact Info

Product

Resources

About