Valence and Rydberg excitations of 3-fluorotoluene in the 4.4–10.8 eV photoabsorption energy region

Funding Information: EB, ASB and MHFB acknowledge support from the Brazilian agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ( CAPES ) and the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico ( CNPq ). EB, ASB and MHFB also acknowledge Prof. Carlos de Carvalho for computational support at LFTC-DFis-UFPR and at LCPAD-UFPR. The authors wish to acknowledge the beam time at the ISA synchrotron, Aarhus University, Denmark. PLV also acknowledges his visiting professor position at Federal University of Paraná, Curitiba, Brazil. This contribution is also based upon work from the COST Action CA18212-Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology). Publisher Copyright: © 2023 The AuthorsThe absolute photoabsorption cross sections for 3-fluorotoluene in the 4.4–10.8 eV energy-range were obtained for the first-time using a synchrotron radiation light source. New theoretical calculations, providing vertical excitation energies and oscillator strengths, were performed at the time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations to qualitatively support the experimental data. The electronic transitions discernible in the photoabsorption spectrum have been assigned to valence, mixed valence-Rydberg and Rydberg transitions. Additionally, a comprehensive assignment of the vibronic structure was performed with the main contribution of C–H in plane bending mode progressions dictating the spectroscopy of the lowest-lying absorption band. From the absolute photoabsorption cross sections, the photolysis lifetimes of 3-fluorotoluene in the Earth's atmosphere were also obtained.publishersversionpublishe

Valence and Rydberg excitations of 2-fluorotoluene in the 4.4–10.8 eV photoabsorption energy region

Funding Information: PASR acknowledges support from the Brazilian agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). ASB and MHFB acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). PASR, ASB and MHFB also acknowledge Prof. Carlos de Carvalho for computational support at LFTC-DFis-UFPR and at LCPAD-UFPR. The authors wish to acknowledge the beam time at the ISA synchrotron, Aarhus University, Denmark. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. SK, AIL and PLV acknowledges the Portuguese National Funding Agency (FCT) through research grant CEFITEC (UIDB/00068/2020) . PLV also acknowledges his visiting professor position at Federal University of Paraná, Curitiba, Brazil. This contribution is also based upon work from the COST Action CA18212-Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology). Funding Information: PASR acknowledges support from the Brazilian agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). ASB and MHFB acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). PASR, ASB and MHFB also acknowledge Prof. Carlos de Carvalho for computational support at LFTC-DFis-UFPR and at LCPAD-UFPR. The authors wish to acknowledge the beam time at the ISA synchrotron, Aarhus University, Denmark. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. SK, AIL and PLV acknowledges the Portuguese National Funding Agency (FCT) through research grant CEFITEC (UIDB/00068/2020). PLV also acknowledges his visiting professor position at Federal University of Paraná, Curitiba, Brazil. This contribution is also based upon work from the COST Action CA18212-Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology). Publisher Copyright: © 2023 The Author(s)The electronic state spectroscopy of 2-fluorotoluene in the gas phase has been investigated for the first time using high-resolution vacuum ultraviolet photoabsorption experiments in the 4.4–10.8 eV energy-range, with absolute cross-section measurements obtained. Additionally, we also present a novel set of ab initio calculations (vertical excitation energies and oscillator strengths) at two different levels of theory, equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) and time-dependent density functional theory (TD-DFT). These are used in the assignment of valence, mix valence-Rydberg and Rydberg transitions, with the associated vibronic series analysed. The measured absolute photoabsorption cross-sections have been used to calculate the photolysis lifetime of 2-fluorotoluene in the Earth's atmosphere.publishersversionpublishe

Dynamics of mulatto grass regrowth depending on rotational cattle grazing management.

This study was carried out to characterize the dynamics of forage accumulation during the regrowth of Mulatto grass submitted to rotational grazing strategies. The treatments corresponded to combinations between two pre-grazing conditions (95% and a maximum light interception during regrowth—LI95% and LIMax) and two post-grazing conditions (post-grazing heights of 15 and 20 cm), according to a 2 × 2 factorial arrangement and randomized complete block design, with four replications. Rates of leaf growth (LGR), stems growth (SGR), total growth (TGR), leaf senescence (LSR), grass accumulation (GAR) (kg·ha−1 ·day−1 ), and the senescence/canopy growth ratio during different stages of regrowth. There was no difference between the management strategies for TGR. However, a higher GAR was reported for pastures managed with LI95% relative to LIMax, of 161.7 and 120.2 kg DM ha−1 ·day−1 , respectively. Pastures managed with LI95% have a lower SGR in the intermediate and final regrowth period, reflecting the efficient control in the stalks production. On the other hand, in pastures managed, the LIMax showed higher SGR and LSR in the final regrowth phase. Thus, the LAI was higher in pastures managed at LI95% compared to those managed at LIMax, of 163.9 and 112.7 kg DM ha−1 ·day−1 , respectively. Mulatto grass pastures, which were managed at LI95% pre-grazing, corresponded to approximately 30 cm in height, showed higher LAI, and ensured a low SGR throughout the regrowth period, constituting a more efficient management strateg

Stabilities of nanohydrated thymine radical cations: insights from multiphoton ionization experiments and ab initio calculations

Multi-photon ionization experiments have been carried out on thymine-water clusters in the gas phase. Metastable H2O loss from T+(H2O)n was observed at n ≥ 3 only. Ab initio quantum-chemical calculations of a large range of optimized T+(H2O)n conformers have been performed up to n = 4, enabling binding energies of water to be derived. These decrease smoothly with n, consistent with the general trend of increasing metastable H2O loss in the experimental data. The lowest-energy conformers of T+(H2O)3 and T+(H2O)4 feature intermolecular bonding via charge-dipole interactions, in contrast with the purely hydrogen-bonded neutrals. We found no evidence for a closed hydration shell at n = 4, also contrasting with studies of neutral clusters

The VUV electronic spectroscopy of acetone studied by synchrotron radiation

The electronic state spectroscopy of acetone (CH3)2CO has been investigated using high-resolution VUV photoabsorption spectroscopy in the energy range 3.7–10.8 eV. New vibronic structure has been observed, notably in the low energy absorption band assigned to the 11A1 → 11A2 (ny → π*) transition. The local absorption maximum at 7.85 eV has been tentatively attributed to the 41A1 (π → π*) transition. Six Rydberg series converging to the lowest ionisation energy (9.708 eV) have been assigned as well as a newly-resolved ns Rydberg series converging to the first ionic excited state (12.590 eV). Rydberg orbitals of each series have been classified according to the magnitude of the quantum defect (δ) and are extended to higher quantum numbers than in the previous analyses

The electronic states of pyrimidine studied by VUV photoabsorption and electron energy-loss spectroscopy

The electronic state spectroscopy of pyrimidine C4H4N2 has been investigated using both high resolution VUV photoabsorption in the energy range 3.7 to 10.8 eV (335 to 115 nm) and lower resolution electron energy loss in the range 2 to 15 eV. The low energy absorption band, assigned to the (*) 7b2(nN) (11B1 11A1) transition, at 3.85(4) eV and the vibrational progressions superimposed upon it have been observed for the first time, due to the availability of a high-resolution photon beam (0.075 nm), corresponding to 3 meV at the midpoint of the energy range studied. Vibronic coupling has been shown to play an important role dictating the nature of the observed excited states, especially for the lowest 1B1 state. The 21B1 state is proposed to have its origin at 7.026 eV according to the vibrational excitation reported in this energy region (7.8–8.4 eV). New experimental evidence of 41A1 state with a maximum cross section at 8.800 eV is supported by previous ab initio quantum chemical calculations. Rydberg series have been assigned converging to the three lowest ionisation energy limits, 9.32 eV (2B2), 10.41 eV (2B1) and 11.1 eV (2A1 + 2A2) with new members reported for the first time and classified according to the magnitude of the quantum defects (). Additionally, the absolute differential cross section for inelastic electron scattering has been measured for the most intense band from 6.9 to 7.8 eV assigned to 1* (31A1 + 21B2)

Photoabsorption measurements and theoretical calculations of the electronic state spectroscopy of propionic, butyric, and valeric acids

Absolute photoabsorption cross sections of propionic (C2H5COOH), butyric (C3H7COOH), and valeric (C4H9COOH) acids have been measured from the dissociative * nO transition (beginning around 5.0 eV) up to 10.7 eV. This constitutes the first study of the neutral electronic states of propionic and butyric acids at energies above the * nO band, while no previous spectroscopic data is available for valeric acid in the present range. The present assignments are supported by the first theoretical calculations of electronic transition energies and oscillator strengths for these organic acids. In addition, the excitation energies of the vibrational modes of propionic acid in its neutral electronic ground state and the vertical ionisation energies of all three molecules have been calculated for the first time. The He(I) photoelectron spectroscopy of propionic acid has been measured from 10 to 16 eV, revealing new fine structure in the first ionic band

Electronic excitation of tetrafluoroethylene, C2F4

The VUV photoabsorption spectrum of tetrafluoroethylene is reported in the wavelength range; 115–320 nm (10.8–3.9 eV). The result is compared with high-energy electron energy loss spectra (EELS). Electrons of incident energy 100 and 30 eV are analysed post-interaction at scattering angles of 5°, 15° and 30° in the energy loss range; 3.0–15.7 eV. Both the photoabsorption and EELS measurements represent the highest resolution data yet reported. The spectra are found to be in good agreement with each other and generally consistent with previous experimental and theoretical work. New photoabsorption features are observed and Rydberg and vibrational assignments suggested. The He(I) photoelectron spectrum is recorded from 9.7 to 20.9 eV and compared to earlier work. New vibrational structure is observed in the first photoelectron band. Implications relevant to the production of CF2 radicals by photon and electron impact are discussed