Interconnection between Polarization-Detected and Population-Detected Signals: Theoretical Results and Ab Initio Simulations

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(17), P. 7560 - 7573

Published: Aug. 26, 2024

Most of spectroscopic signals are specified by the nonlinear laser-induced polarization. In recent years, population-detection becomes a trend in femtosecond spectroscopy. Polarization-detected (PD) and population-detected fundamentally different, because they determined photoinduced processes acting on disparate time scales. this work, we consider fluorescence-detected (FD) N-wave-mixing (NWM) signal as representative example signals, derive rigorous expression for signal, discuss its approximate variants suitable numerical simulations. This leads us to definition phenomenological FD (PFD) which contains special case all definitions available literature. Then formulate prove population-polarization equivalence (PPE) theorem, states that PFD NWM produced (possibly strong) laser pulses can be evaluated conventional PD effective polarization is transition dipole moment operator. We use PPE theorem construction ab initio protocol simulation 4WM signals. As an example, calculate electronic two-dimensional (2D) spectra gas-phase pyrazine compare them with corresponding 2D spectra.

Language: Английский

---

Study on the Photoinduced Isomerization Mechanism of Isatin N²-diphenylhydrazones Molecular Switch

Acta Physica Sinica, Journal Year: 2024, Volume and Issue: 73(17), P. 173101 - 173101

Published: Jan. 1, 2024

Hydrazone molecular switches have significant application value in supramolecular chemistry. A new type of hydrazone switch, named isatin N²-diphenylhydrazone, has been synthesized. Owing to its cis-trans isomerization characteristics under visible light excitation, ease synthesizing derivatives, and sensitivity external stimuli, it important the field biochemistry. Because forward backward excitation characteristics, is considered a class compound that very suitable for switches, wide fields such as biotechnology. In addition, derivatives exhibits strong interactions with negative ions, which enhances function making four-state switch can be achieved by single molecule. However, photo-induced mechanism these not yet clear, whether there are novel phenomena process also unknown. this work, semi empirical OM2/MRCI based trajectory surface hopping dynamics method adopted systematically study photo induced on E-Z N²-diphenylhydrazones switch. Optimization configuration average lifetime first excited S₁ state obtained using semi-empirical It found E-configuration about 107 fs, quantum yield 16.01%. By calculating two different mechanisms identified. addition traditional revolving around C=N bond, mechanism, i.e. face-to-face twisting rotor part elucidated. time-resolved fluorescence radiation spectrum, predicted may fast quenching phenomenon occurring 75 fs process, slightly faster than decay events (107 fs). The information wavelength-resolved attenuation at times calculated, reflects ultrafast accompanied red shift, ranging from 2.1 × 10⁴ cm^–1 3.4 cm^–1. comparing calculated spectra states, existence “dark states” proposed, possible explanations provided, those related lower yields. research results provide theoretical guidance design switches. synthesis stimuli make compounds extremely valuable switching measurement applications.

Language: Английский

---

Discriminating Clockwise and Counterclockwise Photoisomerization Paths in Achiral Photoswitches by Excited-State Electronic Circular Dichroism

The Journal of Physical Chemistry B, Journal Year: 2024, Volume and Issue: 128(35), P. 8303 - 8312

Published: Aug. 22, 2024

Despite the numerous investigations of photoisomerization reactions from both computational and experimental points view, even in complex environments, to date there is no direct demonstration direction rotation retinal chromophore, initiating vision process several organisms, occurring upon light irradiation. In literature, many proposals have been formulated shed on details this process, most which are extracted semiclassical simulations. Although high hopes held development time-resolved X-ray spectroscopy, I argue work that simpler but less known techniques can be used unravel fascinating photochemical process. fact, chiroptical spectroscopy would unambiguously prove rotatory motion chromophore during by probing excited state chirality, a piece information that, so far, has exclusively atomistic demonstrate statement computing expected response along pathways for models chromophores found nature bound rhodopsins, including nuclear ensemble spectra dynamics simulations, compared with experiments.

Language: Английский

---

Tracking the Electron Density Changes in Excited States: A Computational Study of Pyrazine

The Journal of Physical Chemistry Letters, Journal Year: 2024, Volume and Issue: 15(42), P. 10609 - 10613

Published: Oct. 15, 2024

The development of X-ray free-electron lasers has enabled ultrafast diffraction (XRD) experiments, which are capable resolving electronic and vibrational transitions structural changes in molecules or capturing molecular movies. While time-resolved XRD attracted more attention, the extraction information from signals is challenging requires theoretical support. In this work, we combined scattering theory a trajectory surface hopping approach to resolve dynamical structure photoexcited by studying time evolution electron density between excited states ground state. Using pyrazine molecule as an example, show that key features reaction pathways can be identified, enabling capture associated with for molecule.

Language: Английский

---