Femtosecond XUV induced dynamics of the methyl iodide cation

Ultrashort XUV wavelength-selected pulses obtained with high harmonic generation are used to study the dynamics of molecular cations with state-to-state resolution. We demonstrate this by XUV pump - IR probe experiments on CH3I+ cations and identify both resonant and non-resonant dynamics

A detailed experimental and theoretical study of the femtosecond A -band photodissociation of C H3I

The real time photodissociation dynamics of C H3I from the A band has been studied experimentally and theoretically. Femtosecond pump-probe experiments in combination with velocity map imaging have been carried out to measure the reaction times (clocking) of the different (nonadiabatic) channels of this photodissociation reaction yielding ground and spin-orbit excited states of the I fragment and vibrationless and vibrationally excited (symmetric stretch and umbrella modes) C H3 fragments. The measured reaction times have been rationalized by means of a wave packet calculation on the available ab initio potential energy surfaces for the system using a reduced dimensionality model. A 40 fs delay time has been found experimentally between the channels yielding vibrationless CH3(ν=0) and I(2P3/2) and I*(2P1/2) that is well reproduced by the calculations. However, the observed reduction in delay time between the I and I* channels when the C H3 fragment appears with one or two quanta of vibrational excitation in the umbrella mode is not well accounted for by the theoretical model. © 2008 American Institute of Physics.This work has been financed by the Spanish MEC through Grant Nos. CTQ2005-08493-C02-01, FIS-2007- 62002, and Consolider program “Science and Applications of Ultrafast Ultraintense Lasers” No. CSD2007-00013.Peer Reviewe

Factores de influencia en la intención de abandono escolar temprano: perspectiva del estudiantado

En la actualidad, reducir la tasa de abandono escolar temprano continúa siendo una línea de acción prioritaria para los sistemas educativos de todo el mundo. En este sentido, parece conveniente avanzar en la comprensión de los motivos que predisponen al estudiantado a tomar esta decisión con efectos perturbadores tanto a nivel personal como social. Sensibles con su importancia, este trabajo tiene como objetivo identificar factores de influencia en la intención de abandono escolar temprano. Para ello, adoptamos un enfoque metodológico de carácter cuantitativo a través del procedimiento de encuesta. Su aplicación tuvo lugar en la Comunidad Autónoma de La Rioja (España), donde el problema del abandono escolar temprano constituye un área clave de trabajo en su agenda política. La encuesta se realizó mediante la administración de un cuestionario ad hoc a la población de estudiantes escolarizados en los últimos cursos de la etapa obligatoria y primer curso de la etapa no obligatoria. La muestra participante estuvo constituida por 1157 estudiantes. Los resultados indican que la utilidad atribuida a la actividad de estudio y la facilidad relativa percibida para conseguir el título académico son dos factores de influencia significativa en la intención de abandono escolar temprano. En otro orden, el contexto sociofamiliar del estudiantado y los recursos humanos del centro también son predictores significativos de esta misma intención. Concluimos subrayando la necesidad de abordar el problema del abandono escolar temprano desde un enfoque multidimensional que ayude al estudiantado a tomar conciencia de la utilidad y significado profundo de la tarea educativa, promoviendo al mismo tiempo y de forma relacionada creencias motivacionales positivas sobre el valor del esfuerzo para afrontar con éxito metas educativas valiosas y desafiantes.Reducing early school dropout rates continues to be a priority line of action for education systems worldwide. In this sense, it seems appropriate to advance in the understanding of the factors that predispose students to make this decision, which can have disruptive effects on both personal and social levels. Sensitive to its importance, this work aims to identify factors that influence the intention to drop out of school early. To do so, we adopted a quantitative methodological approach through a survey procedure. Its application took place in the Autonomous Community of La Rioja (Spain), where the problem of early school leaving is a key area of work in its political agenda. The survey was carried out by administering an ad hoc questionnaire to the population of students in the last years of compulsory education and the first year of non-compulsory education. The participating sample consisted of 1157 students. The results indicate that the usefulness attributed to the study activity and the perceived relative ease of obtaining the academic qualification are two factors of significant influence on the intention to drop out of school early. Additionally, the socio-familial context of the students and the human resources of the school are also significant predictors of this same intention. We conclude by stressing the need to address the problem of early school leaving from a multidimensional approach that helps students to become aware of the usefulness and deep meaning of the educational task, while at the same time promoting positive motivational beliefs about the value of effort in order to successfully face valuable and challenging educational goals

Structural dynamics effects on the ultrafast chemical bond cleavage of a photodissociation reaction

The correlation between chemical structure and dynamics has been explored in a series of molecules with increasing structural complexity in order to investigate its influence on bond cleavage reaction times in a photodissociation event. Femtosecond time-resolved velocity map imaging spectroscopy reveals specificity of the ultrafast carbon–iodine (C–I) bond breakage for a series of linear (unbranched) and branched alkyl iodides, due to the interplay between the pure reaction coordinate and the rest of the degrees of freedom associated with the molecular structure details. Full-dimension time-resolved dynamics calculations support the experimental evidence and provide insight into the structure–dynamics relationship to understand structural control on time-resolved reactivity

Femtochemistry under scrutiny: Clocking state-resolved channels in the photodissociation of CH3I in the A -band

The following article appeared inThe Journal of Chemical Physics 152.1 (2020): 014304 and may be found at https://doi.org/10.1063/1.5134473Clocking of electronically and vibrationally state-resolved channels of the fast photodissociation of CH3I in the A-band is re-examined in a combined experimental and theoretical study. Experimentally, a femtosecond pump-probe scheme is employed in the modality of resonant probing by resonance enhanced multiphoton ionization (REMPI) of the methyl fragment in different vibrational states and detection through fragment velocity map ion (VMI) imaging as a function of the time delay. We revisit excitation to the center of the A-band at 268 nm and report new results for excitation to the blue of the band center at 243 nm. Theoretically, two approaches have been employed to shed light into the observations: first, a reduced dimensionality 4D nonadiabatic wavepacket calculation using the potential energy surfaces by Xie et al. [J. Phys. Chem. A 104, 1009 (2000)]; and second, a full dimension 9D trajectory surface-hopping calculation on the same potential energy surfaces, including the quantization of vibrational states of the methyl product. In addition, high level ab initio electronic structure calculations have been carried out to describe the CH3 3pz Rydberg state involved in the (2 + 1) REMPI probing process, as a function of the carbon-iodine (C–I) distance. A general qualitative agreement is obtained between experiment and theory, but the effect of methyl vibrational excitation in the umbrella mode on the clocking times is not well reproduced. The theoretical results reveal that no significant effect on the state-resolved appearance times is exerted by the nonadiabatic crossing through the conical intersection present in the first absorption band. The vibrationally state resolved clocking times observed experimentally can be rationalized when the (2 + 1) REMPI probing process is considered. None of the other probing methods applied thus far, i.e., multiphoton ionization photoelectron spectroscopy, soft X-ray innershell photoelectron spectroscopy, VUV single-photon ionization, and XUV core-to-valence transient absorption spectroscopy, have been able to provide quantum state-resolved (vibrational) clocking times. More experiments would be needed to disentangle the fine details in the clocking times and dissociation dynamics arising from the detection of specific quantum-states of the molecular fragmentsM.L.M.-S. acknowledges financial support through a predoctoral contract from Universidad Complutense de Madrid. M.E.C. is grateful to the Spanish MINECO for a contract through Programa de Técnicos de Apoyo a Infraestructuras. This work was financially supported by the Spanish MINECO and MICIU (Grant Nos. CTQ2016-75880-P, FIS2016-77889-R, and PGC2018-096444- B-I00). This research was carried out within the Unidad Asociada Química Física Molecular between the Departamento de Química Física of Universidad Complutense de Madrid and CSIC. The facilities provided by the Center for Ultrasfast Lasers of Universidad Complutense de Madrid are acknowledge

Femtosecond XUV–IR induced photodynamics in the methyl iodide cation

The time-resolved photodynamics of the methyl iodide cation (CH3I+) are investigated by means of femtosecond XUV-IR pump-probe spectroscopy. A time-delay-compensated XUV monochromator is employed to isolate a specific harmonic, the 9th harmonic of the fundamental 800 nm (13.95 eV, 88.89 nm), which is used as a pump pulse to prepare the cation in several electronic states. A time-delayed IR probe pulse is used to probe the dissociative dynamics on the first excited state potential energy surface. Photoelectrons and photofragment ions - and I+ - are detected by velocity map imaging. The experimental results are complemented with high level ab initio calculations for the potential energy curves of the electronic states of CH3I+ as well as with full dimension on-the-fly trajectory calculations on the first electronically excited state, considering the presence of the IR pulse. The and I+ pump-probe transients reflect the role of the IR pulse in controlling the photodynamics of CH3I+ in the state, mainly through the coupling to the ground state and to the excited state manifold. Oscillatory features are observed and attributed to a vibrational wave packet prepared in the state. The IR probe pulse induces a coupling between electronic states leading to a slow depletion of fragments after the cation is transferred to the ground states and an enhancement of I+ fragments by absorption of IR photons yielding dissociative photoionization. © 2021 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft

Femtosecond XUV–IR induced photodynamics in the methyl iodide cation

The time-resolved photodynamics of the methyl iodide cation (CH3I+) are investigated by means of femtosecond XUV–IR pump–probe spectroscopy. A time-delay-compensated XUV monochromator is employed to isolate a specific harmonic, the 9th harmonic of the fundamental 800 nm (13.95 eV, 88.89 nm), which is used as a pump pulse to prepare the cation in several electronic states. A time-delayed IR probe pulse is used to probe the dissociative dynamics on the first excited $\tilde {A}\enspace {}^{2}\mathrm{A}_{1}$ state potential energy surface. Photoelectrons and photofragment ions—${\mathrm{C}\mathrm{H}}_{3}^{+}$ and I+—are detected by velocity map imaging. The experimental results are complemented with high level ab initio calculations for the potential energy curves of the electronic states of CH3I+ as well as with full dimension on-the-fly trajectory calculations on the first electronically excited state $\tilde {A}\enspace {}^{2}\mathrm{A}_{1}$, considering the presence of the IR pulse. The ${\mathrm{C}\mathrm{H}}_{3}^{+}$ and I+ pump–probe transients reflect the role of the IR pulse in controlling the photodynamics of CH3I+ in the $\tilde {A}\enspace {}^{2}\mathrm{A}_{1}$ state, mainly through the coupling to the ground state $\tilde {X}\enspace {}^{2}\mathrm{E}_{3/2,1/2}$ and to the excited $\tilde {B}\enspace {}^{2}\mathrm{E}$ state manifold. Oscillatory features are observed and attributed to a vibrational wave packet prepared in the $\tilde {A}\enspace {}^{2}\mathrm{A}_{1}$ state. The IR probe pulse induces a coupling between electronic states leading to a slow depletion of ${\mathrm{C}\mathrm{H}}_{3}^{+}$ fragments after the cation is transferred to the ground $\tilde {X}\enspace {}^{2}\mathrm{E}_{3/2,1/2}$ states and an enhancement of I+ fragments by absorption of IR photons yielding dissociative photoionization

Mindchanger identification, analysis and recognition: youth perceptions

Youth participation and activism are considered key factors in making the world a fairer, more inclusive, and sustainable place. In line with this idea, in this work, we aim to understand how young people who actively participate in social organizations perceive the characteristics that define young mindchangers. By this concept, we refer to a young citizen who is committed to social justice and willing to change societys mindsets and catalyse active participation among their peers. In our research design, we adopted a quantitative methodological approach using a survey procedure. The results reveal a high level of agreement on the traits that define a Mindchanger. We conclude by emphasizing that the characteristics to which young respondents attribute the highest importance, such as promoter of change, open-minded, interest in global issues, open to international solidarity and empathy, appear to have the greatest influence on the likelihood of becoming a Mindchanger

Newborn Screening for SCID: Experience in Spain (Catalonia)

Linfocitos T; Cribado de recién nacidos; Inmunodeficiencia combinada severaLimfòcits T; Cribratge de nounats; Immunodeficiència combinada severaT-lymphocytes; Newborn screening; Severe combined immunodeficiencyNewborn screening (NBS) for severe combined immunodeficiency (SCID) started in Catalonia in January-2017, being the first Spanish and European region to universally include this testing. In Spain, a pilot study with 5000 samples was carried out in Seville in 2014; also, a research project with about 35,000 newborns will be carried out in 2021–2022 in the NBS laboratory of Eastern Andalusia. At present, the inclusion of SCID is being evaluated in Spain. The results obtained in the first three and a half years of experience in Catalonia are presented here. All babies born between January-2017 and June-2020 were screened through TREC-quantification in DBS with the Enlite Neonatal TREC-kit from PerkinElmer. A total of 222,857 newborns were screened, of which 48 tested positive. During the study period, three patients were diagnosed with SCID: an incidence of 1 in 74,187 newborns; 17 patients had clinically significant T-cell lymphopenia (non-SCID) with an incidence of 1 in 13,109 newborns who also benefited from the NBS program. The results obtained provide further evidence of the benefits of early diagnosis and curative treatment to justify the inclusion of this disease in NBS programs. A national NBS program is needed, also to define the exact SCID incidence in Spain