Conical intersection and coherent vibrational dynamics in alkyl iodides captured by attosecond transient absorption spectroscopy

Chang, Kristina F.; Wang, H.; Poullain, Sonia Marggi; González‐Vázquez, Jesús; Bañares, Luis; Neumark, Daniel M.; Leone, Stephen R.

doi:10.1063/5.0086775

Cited by 13 publications

(18 citation statements)

References 48 publications

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“…At long time delays (Δ t > 100 fs), the differential absorption displayed in Figure (and in Figure S3 as an outline) shows bleach features (defined as a negative absorption change) at 50.6, 52.2, 54.3, and 56 eV associated with the depletion of ground-state AcI and induced absorption features (defined as positive absorption changes) associated with atomic resonances of iodine previously assigned to transitions in ground-state I from 2 P 3/2 → 2 D 5/2 at 46.1 eV, 2 P 3/2 → 2 D 3/2 at 47.8 eV, and 4 d → 6 p /7 p at 55.5 and 57.5 eV and spin–orbit excited I*( 2 P 1/2 → 2 D 3/2 ) at 46.8 eV . The atomic iodine features show a spectral width of ∼300 meV FWHM, and the experimentally measured branching ratio of I*( 2 P 1/2 → 2 D 3/2 ):I( 2 P 3/2 → 2 D 5/2 ) is 1:1.1, after taking into account the differences in the oscillator strengths between the core-level transitions of I and I*. , For comparison, in AcCl, the ratio Cl*:Cl is reported to be 3.3:1, and in AcBr, the ratio Br*:Br is 1:2 . Dissociation of the C–I bond in methyl iodide has been reported to yield a I*:I ratio of 3:1, whereas in i-C 3 H 7 I (nearly the same molecular mass as acetyl iodide), an I*:I ratio of 1:2 was observed .…”

Section: Results and Discussionmentioning

confidence: 93%

“…40 Dissociation of the C−I bond in methyl iodide has been reported to yield a I*:I ratio of 3:1, 26 whereas in i-C 3 H 7 I (nearly the same molecular mass as acetyl iodide), an I*:I ratio of 1:2 was observed. 36 In alkyl iodides, trends in this ratio as a function of alkyl substitution have been attributed to differences in wavepacket bifurcation at a conical intersection between two electronic states along the dissociation coordinate. 36 In AcI, however, cuts through the potential energy surfaces, as shown in Figure S11, reveal the involvement of multiple electronic states in the dissociation dynamics.…”

Section: Iiic Transient Xuv Absorption Spectra and Photodissociation ...mentioning

confidence: 99%

“…Excitation to these dissociative states ultimately leads to the ultrafast dissociation of the C–X bond, yielding an alkyl radical and a halogen atom. The halogen is typically formed in both its ground and spin–orbit excited states due to bifurcation of the excited-state wavepacket at conical intersections along the dissociation coordinate …”

Section: Introductionmentioning

confidence: 99%

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Excited-State Dynamics during Primary C–I Homolysis in Acetyl Iodide Revealed by Ultrafast Core-Level Spectroscopy

et al. 2023

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In typical carbonyl-containing molecules, bond dissociation events follow initial excitation to nπ C�O * states. However, in acetyl iodide, the iodine atom gives rise to electronic states with mixed nπ C�O * and nσ C−I * character, leading to complex excited-state dynamics, ultimately resulting in dissociation. Using ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy and quantum chemical calculations, we present an investigation of the primary photodissociation dynamics of acetyl iodide via time-resolved spectroscopy of core-to-valence transitions of the I atom after 266 nm excitation. The probed I 4d-to-valence transitions show features that evolve on sub-100-fs time scales, reporting on excited-state wavepacket evolution during dissociation. These features subsequently evolve to yield spectral signatures corresponding to free iodine atoms in their spin−orbit ground and excited states with a branching ratio of 1.1:1 following dissociation of the C−I bond. Calculations of the valence excitation spectrum via equation-of-motion coupled cluster with single and double substitutions (EOM-CCSD) show that initial excited states are of spin-mixed character. From the initially pumped spinmixed state, we use a combination of time-dependent density functional theory (TDDFT)-driven nonadiabatic ab initio molecular dynamics and EOM-CCSD calculations of the N 4,5 edge to reveal a sharp inflection point in the transient XUV signal that corresponds to rapid C−I homolysis. By examining the molecular orbitals involved in the core-level excitations at and around this inflection point, we are able to piece together a detailed picture of C−I bond photolysis in which d → σ* transitions give way to d → p excitations as the bond dissociates. We also report theoretical predictions of short-lived, weak 4d → 5d transitions in acetyl iodide, validated by weak bleaching in the experimental transient XUV spectra. This joint experimental−theoretical effort has thus unraveled the detailed electronic structure and dynamics of a strongly spin−orbit coupled system.

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Section: Results and Discussionmentioning

confidence: 93%

Section: Iiic Transient Xuv Absorption Spectra and Photodissociation ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Excited-State Dynamics during Primary C–I Homolysis in Acetyl Iodide Revealed by Ultrafast Core-Level Spectroscopy

et al. 2023

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“…ATAS indirectly probes the NAP through the evolution of absorption peaks, such as the bifurcation or the appearance of new peaks. ,, This is caused by the nuclear WP, initially located in a single electronic state, bifurcating at the NAP and generating new absorption lines. These may evolve independently thereafter due to different gradients in the electronic PESs of the valence states.…”

Section: Probing Nonadiabatic Passages In the Photodissociation Of Th...mentioning

confidence: 99%

Attosecond Monitoring of Nonadiabatic Molecular Dynamics by Transient X-ray Transmission Spectroscopy

Cavaletto

Nam

Rouxel

et al. 2023

J. Chem. Theory Comput.

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Tracing the evolution of molecular coherences can provide a direct, unambiguous probe of nonadiabatic molecular processes, such as the passage through conical intersections of electronic states. Two techniques, attosecond transient absorption spectroscopy (ATAS) and Transient Redistribution of Ultrafast Electronic Coherences in Attosecond Raman Signals (TRUECARS), have been used or proposed for monitoring nonadiabatic molecular dynamics. Both techniques employ the transmission of a weak attosecond extremeultraviolet or X-ray probe to interrogate the molecule at controllable time delays with respect to an optical pump, thereby extracting dynamical information from transient spectral features. The connection between these techniques has not been firmly established yet. In this theoretical study, we provide a unified description of both transient transmission techniques, establishing their relationship as limits of the same pump−probe spectroscopy technique for different pulse parameter regimes. We demonstrate this by quantum dynamical simulations of thiophenol photodissociation and show how complementary coherence information can be revealed by the two techniques.

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“…2021年, Boyer等 [257] 基于pump-probe开展了多 FSSH) [261] 分子动力学计算估计的时间(13 fs)基本一致 [262] . 同时, 测量得到分子基态波包振动频率( cm -1 )也与早期工作测量结果相符合.…”

Section: 阿秒电荷迁移unclassified

Development of attosecond pulses and their application to ultrafast dynamics of atoms and molecules

Tao¹,

Lei²,

Xuan³

et al. 2023

Acta Phys. Sin.

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In the past two decades,the development of laser technology has made attosecond science become a cutting-edge research field,providing various novel perspectives for the study of quantum few-body ultrafast evolution.The attosecond pulses prepared in the current laboratory are widely used in experimental research in the form of isolated pulses or pulse trains.The ultrafast changing light field allows people to control and track the motion of electrons at the atomic-scale,and realizes real-time tracking of electron dynamics on the sub-femtosecond time-scale.This review focuses on the progress in the study of ultrafast dynamics of atoms and molecules,which is an important part of attosecond science.Firstly,the generation and development of attosecond pulses are reviewed,mainly including the principle of high-order harmonic and the separation method of single-attosecond pulses.Then the applications of attosecond pulses are systematically introduced,including photo-ionization time delay,attosecond charge migration,non-adiabatic molecular dynamics and so on.Finally,the summary and outlook of the application of attosecond pulses are presented.

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Conical intersection and coherent vibrational dynamics in alkyl iodides captured by attosecond transient absorption spectroscopy

Cited by 13 publications

References 48 publications

Excited-State Dynamics during Primary C–I Homolysis in Acetyl Iodide Revealed by Ultrafast Core-Level Spectroscopy

Excited-State Dynamics during Primary C–I Homolysis in Acetyl Iodide Revealed by Ultrafast Core-Level Spectroscopy

Attosecond Monitoring of Nonadiabatic Molecular Dynamics by Transient X-ray Transmission Spectroscopy

Development of attosecond pulses and their application to ultrafast dynamics of atoms and molecules

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