Propagation studies for the construction of atomic macro-coherence in dense media as a tool to investigate neutrino physics

In this manuscript we review the possibility of inducing large coherence in a macroscopic dense target by using adiabatic techniques. For this purpose we investigate the degradation of the laser pulse through propagation, which was also related to the size of the prepared medium. Our results show that, although adiabatic techniques offer the best alternative in terms of stability against experimental parameters, for very dense media it is necessary to engineer laser-matter interaction in order to minimize laser field degradation. This work has been triggered by the proposal of a new technique, namely Radiative Emission of Neutrino Pairs (RENP), capable of investigating neutrino physics through quantum optics concepts which require the preparation of a macrocoherent state.Ministerio de Economía y Competitividad (Spain) FIS2014-53371-C4-3-RMinisterio de Economía y Competitividad (Spain) FIS2014-53371-C4-1-

A novel technique to achieve atomic macro-coherence as a tool to determine the nature of neutrinos

The photon spectrum in macro-coherent atomic deexcitation via radiative emission of neutrino pairs has been proposed as a sensitive probe of the neutrino mass spectrum, capable of competing with conventional neutrino experiments. In this paper, we revisit this intriguing possibility, presenting an alternative method for inducing large coherence in a target based on adiabatic techniques. More concretely, we propose the use of a modified version of coherent population return (CPR), namely two-photon CPR, that turns out to be extremely robust with respect to the experimental parameters and capable of inducing a coherence close to 100 % in the target.This work was supported by Ministerio de Economía y Competitividad (Spain) Projects FIS2014-53371-C4-3-R and FIS2014-53371-C4-1-R

Tracking ultrafast dynamics by sub-20-fs UV pulses generated in the lab open atmosphere

This study describes a simple method to generate sub-20 fs UV-pulses (264 nm) by third-harmonic generation, in an air-plasma filament formed after focusing the fundamental 800 nm beam directly in the lab open-atmosphere. The generated pulses are applied to track the relaxation through the conical intersection that couples the S2 and S1 states, in the benchmark molecule of naphthalene. The transients, with a resolution of about 25 fs, show two differentiate patterns of quantum beats. The assignation of these oscillations to specific modes in the lower S1 state and to electronic coherence between the two coupled states is discussed.All the experiments were carried out at the CLPU facility. The authors acknowledge the assistance from the CLPU technical and administrative personnel. They also thank the financial support from the Spanish MINECO through the grant: PGC2018-098561-B-C21. The work was also funded by the Basque Government (IT1162-19 and IT1491-22). I. Lamas thanks the UPV/EHU for his predoctoral fellowship. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, ESF) is also gratefully acknowledged. The authors greatly appreciate the Open Access funding provided by University of Basque Country

Femtosecond evolution of the pyrrole molecule excited in the near part of its UV spectrum

The evolution of the isolated pyrrole molecule has been followed after excitation in the 265–217 nm range by using femtosecond time delayed ionization. The transients collected in the whole excitation range show the vanishing of the ionization signal in the femtosecond time scale, caused by the relaxation along a πσ* type state (3s a1←π 1a2), which is the lowest excited electronic state of the molecule. This surface is dissociative along the NH bond, yielding a 15 ± 3 fs lifetime that reflects the loss of the ionization cross-section induced by the ultrafast wavepacket motion. Although a weak πσ* absorption is detected, the state is mainly reached through internal conversion of the higher bright ππ* transitions, which occurs with a 19 ± 3 fs lifetime. In addition to its resonant excitation, the intense ππ* absorption extending in the 220–190 nm interval is also out-of-resonance populated at energies far to the red from its absorption onset. This coherent adiabatic excitation of the ππ* transition should follow the excitation pulse (coherent population return effect), but instead the system relaxes toward the lower πσ* surface through a conical intersection during the interaction time, leading to the population of πσ* state at wavelengths as long as 265 nm. According to the observed behavior, the time evolution of the system in the full excitation range studied is modeled by a coherent treatment that provides key insights on the photophysical properties of the molecule.This study was funded by Spanish MICINN (Grant No. CTQ2010-17749) and Consolider Program “Science and Applications of Ultrafast Ultraintense Lasers” (Grant No. CSD2007-00013), and by the Basque Government through the “Ayudas para apoyar las actividades de grupos de investigación del sistema universitario vasco” program. The experiments and theoretical calculations were carried out at the SGIker laser facility, and IZO-SGI of the UPV/EHU, respectively

An initial study on atmospheric pressure ion transport by laser ionization and electrostatic fields.

Laser ionization of mixtures of gases at atmospheric pressure and the subsequent transport through electrostatic field is studied. A prototype is designed to perform the transport and detection of the ions. Relevance of the composition of the mixture of gases and ionization parameters is show

Plasma dynamics studies by mass spectrometry techniques

We present temporal information obtained by mass spectrometry techniques about the evolution of plasmas generated by laser filamentation in air. The experimental setup used in this work allowed us to study not only the dynamics of the filament core but also of the energy reservoir that surrounds it. Furthermore, valuable insights about the chemistry of such systems like the photofragmentation and/or formation of molecules were obtained. The interpretation of the experimental results are supported by PIC simulations

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic