Vibrationally assisted below-threshold ionization

Horton, Spencer; Liu, Yusong; Chakraborty, Pratip; Matsika, Spiridoula; Weinacht, Thomas

doi:10.1103/physreva.95.063413

Cited by 9 publications

(4 citation statements)

References 29 publications

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“…AKEs were computed on top of the triplet state minima for the first time, triplet to doublet gaps being extremely large, making the probe pulses here employed (5.2 eV) unable to ionise the systems (Cyd being the only case ionised with an AKE B 0.08 eV) and thus suggesting the move to even more energetic probe pulses (vacuum UV) for their characterization. 103 The CT state, on the other hand, shows smaller singlet to doublet gaps, readily accessible for photoelectron studies with less energetic probe pulses. Our estimates reveal larger AKEs to those found in the FC region for all systems, being B3 eV and over an eV larger than those registered for FC, and even larger towards the CI with the ground state, thus being a unique fingerprint for their characterization.…”

Section: Spectral Signalsmentioning

confidence: 99%

UV-induced long-lived decays in solvated pyrimidine nucleosides resolved at the MS-CASPT2/MM level

Pepino

Segarra‐Martí

Nenov

et al. 2018

Phys. Chem. Chem. Phys.

114

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The most relevant 'dark' electronic excited states in DNA/RNA pyrimidine nucleosides are mapped in water employing hybrid MS-CASPT2/MM optimisations with explicit solvation and including the sugar. Conical intersections (CIs) between initially accessed bright ππ* and the lowest energy darknπ* excited states, involving the lone pair localised on the oxygen and/or nitrogen atoms are characterised. They are found in the vicinities of the Franck-Condon (FC) region and are shown to facilitate non-adiabatic population transfer. The excited state population of the nπ* state, localised in the carbonyl moiety on all pyrimidine nucleosides, is predicted to rapidly evolve to its minimum, displaying non-negligible potential energy barriers along its non-radiative decay, and accounting for the ps signal registered in pump-probe experiments as well as for an efficient population of the triplet state. Cytidine displays an additional nπ* state localised in the N3 atom and that leads to its excited state minimum displaying large potential energy barriers in the pathway connecting to the CI with the ground state. Sugar-to-base hydrogen/proton transfer processes are assessed in solution for the first time, displaying a sizable barrier along its decay and thus being competitive with other slow decay channels in the ps and ns timescales. A unified deactivation scheme for the long-lived channels of pyrimidine nucleosides is delivered, where the nπ* state is found to mediate the long-lived decay in the singlet manifold and act as the doorway for triplet population and thus accounting for the recorded phosphorescence and, more generally, for the transient/photoelectron spectral signals registered up to the ns timescale.

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Section: Spectral Signalsmentioning

confidence: 99%

UV-induced long-lived decays in solvated pyrimidine nucleosides resolved at the MS-CASPT2/MM level

Pepino

Segarra‐Martí

Nenov

et al. 2018

Phys. Chem. Chem. Phys.

114

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“…The ring-opening dynamics of CHD after excitation from the HOMO to the lowest unoccupied molecular orbital via one-photon absorption (1PA) is one of the most actively studied dynamics in time-resolved spectroscopy [26,27,[29][30][31][32][33][34][35][36][37][38][39][40]. Most studies reported that the ring-opening step in the isomerization process is completed in less than 200 fs after photoexcitation.…”

Section: Ultrafast Photo-isomerization Of 13-cyclohexadienementioning

confidence: 99%

Time-resolved high-harmonic spectroscopy of ultrafast photoisomerization dynamics

Kaneshima¹,

Ninota²,

Sekikawa³

2018

Opt. Express

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We report the first time-resolved high-harmonic spectroscopy (TR-HHS) study of a chemical bond rearrangement. We investigate the transient change of the high-harmonic signal from 1,3-cyclohexadiene (CHD), which undergoes ring-opening and isomerizes to 1,3,5-hexatriene (HT) upon photoexcitation. We associated the harmonic yield variation with the changes in the molecule's electronic state and vibrational frequencies, which are caused by isomerization. This showed us that the electronic excited state of CHD created through two-photon absorption of 3.1 eV photons relaxes almost completely within 100 fs to the electronic ground state of CHD with vibrational excitation. Subsequently, the molecule isomerizes to HT (i.e., ring-opening occurs, around 400 fs after the excitation). The present results demonstrate that TR-HHS, which can track both electronic and nuclear dynamics, is a powerful tool for studying ultrafast photochemical reactions.

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“…76 This makes use of an established methodology producing the fifth harmonic of a Ti:Sapphire laser (160 nm) in a static gas cell via non-collinear four-wave mixing. 77,78 Such an approach has also been demonstrated previously for use as a probe in other time-resolved studies of non-adiabatic molecular processes, [79][80][81][82] as have related variations employing the sixth harmonic (133 nm) [83][84][85][86] and ninth harmonic (90 nm). 87 To undertake experiments using a VUV probe beam, an auxiliary differentially pumped vacuum chamber is incorporated into the existing VMI spectrometer from Fig.…”

Section: Extending the View Along The Reaction Coordinatementioning

confidence: 92%