Predicting the photodynamics of cyclobutanone triggered by a laser pulse at 200 nm and its MeV-UED signals -- a trajectory surface hopping and XMS-CASPT2 perspective
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2024
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| _version_ | 1866913496417959936 |
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| author | Janoš, Jiří Nunes, Joao Pedro Figueira Hollas, Daniel Slavíček, Petr Curchod, Basile F. E. |
| author_facet | Janoš, Jiří Nunes, Joao Pedro Figueira Hollas, Daniel Slavíček, Petr Curchod, Basile F. E. |
| contents | This work is part of a prediction challenge that invited theoretical/computational chemists to predict the photochemistry of cyclobutanone in the gas phase, excited at 200 nm by a laser pulse, and the expected signal that will be recorded during a time-resolved megaelectronvolt ultrafast electron diffraction (MeV-UED). We present here our theoretical predictions based on a combination of trajectory surface hopping with XMS-CASPT2 (for the nonadiabatic molecular dynamics) and Born-Oppenheimer molecular dynamics (BOMD) with MP2 (for the athermal ground-state dynamics following internal conversion), coined (NA+BO)MD. The initial conditions were sampled from BOMD coupled to a quantum thermostat. Our simulations indicate that the main photoproducts after 2 ps of dynamics are CO + cyclopropane (50%), CO + propene (10%), and ethene and ketene (34%). The photoexcited cyclobutanone in its second excited electronic state S$_2$ can follow two pathways for its nonradiative decay: (i) a ring-opening in S$_2$ and a subsequent rapid decay to the ground electronic state, where the photoproducts are formed, or (ii) a transfer through a closed-ring conical intersection to S$_1$, where cyclobutanone ring opens and then funnels to the ground state. Lifetimes for the photoproduct and electronic populations were determined. We calculated a stationary MeV-UED signal [difference pair distribution function - $Δ$PDF$(r)$] for each (interpolated) pathway as well as a time-resolved signal [$Δ$PDF$(r,t)$ and $ΔI/I(s,t)$] for the full swarm of (NA+BO)MD trajectories. Furthermore, our analysis provides time-independent basis functions that can be used to fit the time-dependent experimental UED signals and potentially recover the population of photoproducts. We also offer a detailed analysis of the limitations of our model and their potential impact on the predicted experimental signals. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2402_05801 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Predicting the photodynamics of cyclobutanone triggered by a laser pulse at 200 nm and its MeV-UED signals -- a trajectory surface hopping and XMS-CASPT2 perspective Janoš, Jiří Nunes, Joao Pedro Figueira Hollas, Daniel Slavíček, Petr Curchod, Basile F. E. Chemical Physics This work is part of a prediction challenge that invited theoretical/computational chemists to predict the photochemistry of cyclobutanone in the gas phase, excited at 200 nm by a laser pulse, and the expected signal that will be recorded during a time-resolved megaelectronvolt ultrafast electron diffraction (MeV-UED). We present here our theoretical predictions based on a combination of trajectory surface hopping with XMS-CASPT2 (for the nonadiabatic molecular dynamics) and Born-Oppenheimer molecular dynamics (BOMD) with MP2 (for the athermal ground-state dynamics following internal conversion), coined (NA+BO)MD. The initial conditions were sampled from BOMD coupled to a quantum thermostat. Our simulations indicate that the main photoproducts after 2 ps of dynamics are CO + cyclopropane (50%), CO + propene (10%), and ethene and ketene (34%). The photoexcited cyclobutanone in its second excited electronic state S$_2$ can follow two pathways for its nonradiative decay: (i) a ring-opening in S$_2$ and a subsequent rapid decay to the ground electronic state, where the photoproducts are formed, or (ii) a transfer through a closed-ring conical intersection to S$_1$, where cyclobutanone ring opens and then funnels to the ground state. Lifetimes for the photoproduct and electronic populations were determined. We calculated a stationary MeV-UED signal [difference pair distribution function - $Δ$PDF$(r)$] for each (interpolated) pathway as well as a time-resolved signal [$Δ$PDF$(r,t)$ and $ΔI/I(s,t)$] for the full swarm of (NA+BO)MD trajectories. Furthermore, our analysis provides time-independent basis functions that can be used to fit the time-dependent experimental UED signals and potentially recover the population of photoproducts. We also offer a detailed analysis of the limitations of our model and their potential impact on the predicted experimental signals. |
| title | Predicting the photodynamics of cyclobutanone triggered by a laser pulse at 200 nm and its MeV-UED signals -- a trajectory surface hopping and XMS-CASPT2 perspective |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2402.05801 |