Resonance-enhanced multiphoton ionization spectra of jet-cooled methanol and ethanol

Philis, John G.

doi:10.1016/j.cplett.2007.10.089

Cited by 12 publications

(7 citation statements)

References 33 publications

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“…32,33 Analysis of the fragment kinetic energy distributions for the O-H and C-O dissociation channels revealed that most of the available energy is channeled into translational kinetic energy, which also supports the possible mechanism of prompt fragmentation on the S 1 PES, which connects asymptotically to the CH 3 O + H and CH 3 + OH thermodynamic limits. 32,33,[35][36][37] In the valence isoelectronic system CH 3 SH, the S 1 and S 2 surfaces were previously explored by neutral fragment velocity map imaging 38 and ab initio theory. 8,39,40 In CH 3 SH, a conical intersection between the S 2 and S 1 PESs, involving C-S bond stretch and S-H motion, enables dissociation.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Champenois

Greenman

Shivaram

et al. 2019

The Journal of Chemical Physics

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The electronic and nuclear dynamics in methanol, following 156 nm photoexcitation, are investigated by combining a detailed analysis of time-resolved photoelectron spectroscopy experiments with electronic structure calculations. The photoexcitation pump pulse is followed by a delayed 260 nm photoionization probe pulse, to produce photoelectrons that are analyzed by velocity map imaging. The yield of mass-resolved ions, measured with similar experimental conditions, are found to exhibit the same time-dependence as specific photoelectron spectral features. Energy-resolved signal onset and decay times are extracted from the measured photoelectron spectra to achieve high temporal resolution, beyond the 20 fs pump and probe pulse durations. When combined with ab initio calculations of selected cuts through the excited state potential energy surfaces, this information allows the dynamics of the transient excited molecule, which exhibits multiple nuclear and electronic degrees of freedom, to be tracked on its intrinsic few-femtosecond timescale. Within 15 fs of photoexcitation, we observe nuclear motion on the initially bound photoexcited 2 1 A (S 2 ) electronic state, through a conical intersection with the 1 1 A (S 3 ) state, which reveals paths to photodissociation following C-O stretch and C-O-H angle opening.

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Section: Introductionmentioning

confidence: 99%

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Champenois

Greenman

Shivaram

et al. 2019

The Journal of Chemical Physics

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“…In the case of NO, lengthening of the fluorescence lifetime of a molecular Rydberg state when going from isolation to condensed media points to the fact that the local structure of the solvent environment has considerable influence on the transition dipole. Furthermore, because of mixing of Rydberg orbitals with the solvent continuum, the characterization of these orbitals below the VIE provides invaluable information on the competing ionization and dissociation channels. ,, Albrecht and coworkers considered liquid benzene and benzene diluted in hexane via two-photon excitation spectra. , This study pointed out that the dominance of a Rydberg excitation between 6 and 7 eV, which was well known in the gas phase, also played an important role in the liquid solution. The favorable selection rules for two-photon excitation were important in uncovering this state.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure of Liquid Methanol and Ethanol from Polarization-Dependent Two-Photon Absorption Spectroscopy

et al. 2019

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Two-photon absorption (2PA) spectra of liquid methanol and ethanol are reported for the energy range 7–10 eV from the first electronic excitation to close to the liquid-phase ionization potential. The spectra give detailed information on the electronic structures of these alcohols in the bulk liquid. The focus of this Article is to examine the electronic structure change compared with water on substitution of a hydrogen by an alkyl group. Continuous 2PA spectra are recorded in the broadband pump–probe fashion, with a fixed pump pulse in the UV region and a white-light continuum as a probe. Pump pulses of two different energies, 4.6 and 6.2 eV, are used to cover the spectral range up to 10 eV. In addition, theoretical 2PA cross sections for both molecules isolated in the gas phase are computed by the equation-of-motion coupled-cluster method with single and double substitutions (EOM-CCSD). These computational results are used to assign both the experimental 2PA and literature one-photon linear absorption spectra. The most intense spectral features are due to transitions to the Rydberg states, and the 2PA spectra are dominated by the totally symmetric 3p z ← 2p z transition in both alcohols. The experimental 2PA spectra are compared with the simulated 2PA spectra based on ab initio calculations that reveal a general blue shift of the excited transitions upon solvation. The effective 2PA thresholds in methanol and ethanol decrease to 6.9 eV compared with 7.8 eV for water. The analysis of the 2PA polarization ratio leads us to conclude that the excited states of ethanol deviate more markedly from water in the lower energy region compared with methanol. The polarization dependence of the 2PA spectra reveal the symmetries of the excited states within the measured energy range. Natural transition orbital calculations are performed to visualize the nature of the transitions and the orbitals participating during electronic excitation.

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“…The slower CH 3 + products could also be generated from the photodissociation of CH 3 O + , which is produced from the multiphoton ionization of CH 3 OH by the 157 nm laser. 43 However, the contribution of this possible process to the slower CH 3 signals, and the ratio of signal strength for CH 3 arising from CH 3 O versus CH 3 OH cannot be evaluated quantitatively.…”

Section: Resultsmentioning

confidence: 99%

Product pair correlation in CH₃OH photodissociation at 157 nm: the OH + CH₃channel

Chen

Eppink

Jiang

et al. 2011

Phys. Chem. Chem. Phys.

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The OH + CH 3 product channel for the photodissociation of CH 3 OH at 157 nm was investigated using the velocity map imaging technique with the detection of CH 3 radical products via (2+1) resonance-enhanced multiphoton ionization (REMPI). Images were measured for the CH 3 formed in the ground and excited states (v 2 = 0, 1, 2, and 3) of the umbrella vibrational mode and correlated OH vibrational state distributions were also determined. We find that the vibrational distribution of the OH fragment in the OH + CH 3 channel is clearly inverted. Anisotropic distributions for the CH 3 (v 2 = 0, 1, 2, and 3) products were also determined, which is indicative of a fast dissociation process for the C-O bond cleavage. A slower CH 3 product channel was also observed, that is assigned to a two-step photodissociation process, in which the first step is the production of a CH 3 O(X 2 E) radical via the cleavage of the O-H bond in CH 3 OH, followed by probe laser photodissociation of the nascent CH 3 O radicals yielding CH 3 (X 2 A 1 , v = 0) products.

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Resonance-enhanced multiphoton ionization spectra of jet-cooled methanol and ethanol

Cited by 12 publications

References 33 publications

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Electronic Structure of Liquid Methanol and Ethanol from Polarization-Dependent Two-Photon Absorption Spectroscopy

Product pair correlation in CH₃OH photodissociation at 157 nm: the OH + CH₃channel

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Resonance-enhanced multiphoton ionization spectra of jet-cooled methanol and ethanol

Cited by 12 publications

References 33 publications

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Ultrafast photodissociation dynamics and nonadiabatic coupling between excited electronic states of methanol probed by time-resolved photoelectron spectroscopy

Electronic Structure of Liquid Methanol and Ethanol from Polarization-Dependent Two-Photon Absorption Spectroscopy

Product pair correlation in CH3OH photodissociation at 157 nm: the OH + CH3channel

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Product pair correlation in CH₃OH photodissociation at 157 nm: the OH + CH₃channel