Inverting Singlet and Triplet Excited States using Strong Light-Matter Coupling

In organic microcavities, hybrid light-matter states can form with energies that differ from the bare molecular excitation energies by nearly 1 eV. A timely question, given recent advances in the development of thermally activated delayed fluorescence materials, is whether strong light-matter coupling can be used to invert the ordering of singlet and triplet states and, in addition, enhance reverse intersystem crossing (RISC) rates. Here, we demonstrate a complete inversion of the singlet lower polariton and triplet excited states. We also unambiguously measure the RISC rate in strongly-coupled organic microcavities and find that, regardless of the large energy level shifts, it is unchanged compared to films of the bare molecules. This observation is a consequence of slow RISC to the lower polariton due to the delocalized nature of the state across many molecules and an inability to compete with RISC to the dark exciton reservoir, which occurs at a rate comparable to that in bare molecules

Triplet harvesting in the polaritonic regime: a variational polaron approach

We explore the electroluminescence efficiency for a quantum mechanical model of a large number of molecular emitters embedded in an optical microcavity. We characterize the circumstances under which a microcavity enhances harvesting of triplet excitons via reverse intersystem-crossing (R-ISC) into singlet populations that can emit light. For that end, we develop a time-local master equation in a variationally optimized frame which allows for the exploration of the population dynamics of chemically relevant species in different regimes of emitter coupling to the condensed phase vibrational bath and to the microcavity photonic mode. For a vibrational bath that equilibrates faster than R-ISC (in emitters with weak singlet-triplet mixing), our results reveal that significant improvements in efficiencies with respect to the cavity-free counterpart can be obtained for strong coupling of the singlet exciton to a photonic mode, as long as the singlet to triplet exciton transition is within the inverted Marcus regime; under these circumstances, we show the possibility to overcome the detrimental delocalization of the polariton states across a macroscopic number of molecules. On the other hand, for a vibrational bath that equilibrates slower than R-ISC (i.e., emitters with strong singlet-triplet mixing), we find that while enhancemnents in photoluminiscence can be obtained via vibrational relaxation into polaritons, this only occurs for small number of emitters coupled to the photon mode, with delocalization of the polaritons across many emitters eventually being detrimental to electroluminescence efficiency. These findings provide insight on the tunability of optoelectronic processes in molecular materials due to weak and strong light-matter coupling

Can ultrastrong coupling change ground state chemical reactions?

Recent advancements on the fabrication of organic micro- and nanostructures have permitted the strong collective light-matter coupling regime to be reached with molecular materials. Pioneering works in this direction have shown the effects of this regime in the excited state reactivity of molecular systems and at the same time has opened up the question of whether it is possible to introduce any modifications in the electronic ground energy landscape which could affect chemical thermodynamics and/or kinetics. In this work, we use a model system of many molecules coupled to a surface-plasmon field to gain insight on the key parameters which govern the modifications of the ground-state Potential Energy Surface (PES). Our findings confirm that the energetic changes per molecule are determined by single-molecule-light couplings which are essentially local, in contrast with those of the electronically excited states, for which energetic corrections are of a collective nature. Still, we reveal some intriguing quantum-coherent effects associated with pathways of concerted reactions, where two or more molecules undergo reactions simultaneously, and which can be of relevance in low-barrier reactions. Finally, we also explore modifications to nonadiabatic dynamics and conclude that, for this particular model, the presence of a large number of dark states yields negligible changes. Our study reveals new possibilities as well as limitations for the emerging field of polariton chemistry

Infrared Irradiation, an Excellent, Alternative Green Energy Source

In this chapter, attending the request by the UNESCO, Decade to Educate in the Sustainability, a green-chemical approach is offered. Thus, the most recent advances using the infrared irradiation as alternative energy source are given; this is in order to activate an organic reaction in addition to conveniently perform the extractions of secondary metabolites. It is worth noting that this manuscript is an improved extent of a review previously reported by our group. The chapter is accomplished considering two sections, displaying a comprehensive overview: in a first instance, after a deep search in the literature, a broad compilation of suitable information is presented; in a second landscape, recent unpublished results from our and other laboratories are described

Polariton-assisted Singlet Fission in Acene Aggregates

Singlet fission is an important candidate to increase energy conversion efficiency in organic photovoltaics by providing a pathway to increase the quantum yield of excitons per photon absorbed in select materials. We investigate the dependence of exciton quantum yield for acenes in the strong light-matter interaction (polariton) regime, where the materials are embedded in optical microcavities. Starting from an open-quantum-systems approach, we build a kinetic model for time-evolution of species of interest in the presence of quenchers and show that polaritons can decrease or increase exciton quantum yields compared to the cavity-free case. In particular, we find that hexacene, a typically poor singlet-fission candidate, can feature a higher yield than cavity-free pentacene when assisted by polaritonic effects. Similarly, we show that pentacene yield can be increased when assisted by polariton states. Finally, we address how various relaxation processes between bright and dark states in lossy microcavities affect polariton photochemistry. Our results also provide insights on how to choose microcavities to enhance similarly related chemical processes.Comment: 12 pages, 4 figure

La inimputabilidad de las personas con discapacidad

La Convención Internacional de los derechos de las personas con discapacidad ha promovido en su artículo 12 la capacidad de jurídica de éstas; y ha provocado que en nuestro derecho interno se publique la derogación de la inhabilitación en la Ley 8/2021, regulando en sustitución las medidas de apoyo. Dicha ley es un instrumento legislativo idóneo para que las condiciones de igualdad de todos los derechos humanos y libertades fundamentales de todas las personas con discapacidad se puedan ejercer sin ningún menoscabo. En este trabajo explico cómo una persona con discapacidad, manteniendo su capacidad jurídica, puede resultar una persona inimputable a nivel penal, siempre y cuando se den las condiciones para ello, pero además también puede resultar semi imputable; pudiendo ser ambas figuras el origen de imposición de medidas de seguridad para las personas que hayan cometido un delito y tengan ciertos elementos en su personalidad que muestren una peligrosidad delictiva. A su vez también pongo de manifiesto de una manera más breve, pero no por ello menos importante, la necesidad de creación de más centros de educación especial y la formación del personal Policial, de la administración de justicia, del personal penitenciario, y en definitiva, de todos los agentes participantes en el proceso penal.Article 12 of the International Convention on the Rights of Persons with Disabilities has promoted their legal capacity; and it has caused the repeal of the derogation of Law 8/2021 to be published in our internal law, regulating the support measures in substitution. Said law is an ideal legislative instrument so that the conditions of equality of all human rights and fundamental freedoms of all persons with disabilities can be ensured without any undermining. End od degree proyect I explain how a person with a disability, maintaining their legal capacity at all times, can be a person who cannot be criminally charged, as long as the necessary conditions are met; and it can also be semi attributable; both figures being able to generate the imposition of security measures when a crime is committed and there are certain elements of their personality that show criminal dangerousness. At the same time, I also highlight in a shorter, but not less important, the need to create more special education centers and the training of Police personnel, the administration of justice, prison personnel, and ultimately , of all the agents participating in the criminal process

On the nuclear robustness of the r process in neutron-star mergers

We have performed r-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic simulation. Our calculations consider an extended nuclear network, including spontaneous, $\beta$- and neutron-induced fission and adopting fission yield distributions from the ABLA code. We have studied the sensitivity of the r-process abundances to nuclear masses by using different models. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed r-process abundance (the second and third peaks, the rare-earth peak and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the abundance yields at and just above the third peak, which can be traced back to different predictions of neutron separation energies for r-process nuclei around neutron number $N=130$. The remaining trajectories, which contribute 10% by mass to the total integrated abundances, follow such a fast expansion that the r process does not use all the neutrons. This also leads to a larger variation of abundances among trajectories as fission does not dominate the r-process dynamics. The total integrated abundances are dominated by contributions from the slow abundances and hence reproduce the general features of the observed r-process abundances. We find that at timescales of weeks relevant for kilonova light curve calculations, the abundance of actinides is larger than the one of lanthanides. Hence actinides can be even more important than lanthanides to determine the photon opacities under kilonova conditions. (Abridged)Comment: 17 pages, 7 figures, resubmitted to PRC addressing referee comment

Relación entre variable sociodemagráfica, rasgos de personalidad, con respecto al rendimiento académico en estudiantes de secundaria del turno nocturno del colegio Villa Libertad, II semestre del 2012

En la presente investigación se analizan algunas variables sociodemográficas, los rasgos de personalidad y el rendimiento académico de los estudiantes de secundaria del turno nocturno del Colegio “Villa Libertad”. Asimismo en este estudio se logra identificar los rasgos de personalidad que predominan en los estudiantes según los factores primarios del Cuestionario 16 FP, además de relacionar ciertas variables sociodemográfica con los rasgos de personalidad y el rendimiento académico. El enfoque de este estudio es cuantitativo, según el nivel de profundidad del conocimiento es una investigación descriptiva y de corte transversal ya que se realizó en un mismo período de tiempo. La muestra estuvo constituida por 65 estudiantes de secundaria desde el 7mo al 11vo grado. Para la recolección de los datos se utilizó el Cuestionario de los 16 Factores de la Personalidad de Raymond Cattell. La información se procesó a través del programa de estadística (R №2.15) además del SPSS, la regresión lineal, t Destudent, y el Anova a fin de correlacionar los datos