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Concept

Inversion de population

Publications associées (26)

Terahertz emission from diamond nitrogen-vacancy centers

László Forró, Ferenc Simon

Coherent light sources emitting in the terahertz range are highly sought after for fundamental research and applications. Terahertz lasers rely on achieving population inversion. We demonstrate the generation of terahertz radiation using nitrogen-vacancy c ...

Amer Assoc Advancement Science2024

Fast in vivo assay of creatine kinase activity in the human brain by P-31 magnetic resonance fingerprinting

Lijing Xin, Mark Stephan Widmaier, Songi Lim, Daniel Wenz

A new and efficient magnetisation transfer P-31 magnetic resonance fingerprinting (MT-P-31-MRF) approach is introduced to measure the creatine kinase metabolic rate kCK

{k}_{\mathrm{CK}}

between phosphocreatine (PCr) and adenosine triphosphate (ATP) i ...

WILEY2023

Search for long-lasting electronic coherence using on-the-fly ab initio semiclassical dynamics

Jiri Vanicek, Nikolay Golubev, Alan Scheidegger

Using a combination of high-level ab initio electronic structure methods with efficient on-the-fly semiclassical evaluation of nuclear dynamics, we performed a massive scan of small polyatomic molecules searching for a long-lasting oscillatory dynamics of ...

AIP Publishing2022

How free exciton-exciton annihilation lets bound exciton emission dominate the photoluminescence of 2D-perovskites under high-fluence pulsed excitation at cryogenic temperatures

Michael Graetzel, Jovana Milic, Algirdas Ducinskas

Photoluminescence (PL) spectra of atomically thin 2D lead iodide perovskite films are shown to depend on excited-state density, especially at cryogenic temperatures. At high excited-state densities and low temperatures, free exciton (FE) emission is so sup ...

AMER INST PHYSICS2021

Electronic Population Transfer via Impulsive Stimulated X-Ray Raman Scattering with Attosecond Soft-X-Ray Pulses

Christoph Bostedt, Andre Al Haddad, Solène Oberli

Free-electron lasers provide a source of x-ray pulses short enough and intense enough to drive nonlinearities in molecular systems. Impulsive interactions driven by these x-ray pulses provide a way to create and probe valence electron motions with high tem ...

AMER PHYSICAL SOC2020

Using flow cytometry and light-induced fluorescence to characterize the variability and characteristics of bioaerosols in springtime in Metro Atlanta, Georgia

Athanasios Nenes

The abundance and speciation of primary biological aerosol particles (PBAP) is important for understanding their impacts on human health, cloud formation, and ecosystems. Towards this, we have developed a protocol for quantifying PBAP collected from large ...

Copernicus GmbH2020

Cooling dynamics of electrons in MAPbBr(3) probed in the deep-UV

Majed Chergui, Malte Oppermann, Thomas Charles Henry Rossi, Peter Chen, Lijie Wang

Transient absorption in the Visible and in the deep-UV is performed on MAPbBr(3) thin films with 3.1 eV pump excitation. The UV probe can access higher order transitions in the material exploring different high-symmetry points of the Brillouin zone. Uncorr ...

E D P SCIENCES2019

Ultrafast Structural Dynamics along the beta - gamma Phase Transition Path in MnAs

Eugenio Ferrari

We investigate the orthorhombic distortion and the structural dynamics of epitaxial MnAs layers on GaAs(001) using static and time-resolved x-ray diffraction. Laser-induced intensity oscillations of Bragg reflections allow us to identify the optical phonon ...

AMER PHYSICAL SOC2019

Topological phonons and thermoelectricity in triple-point metals

Quansheng Wu

Recently published discoveries of acoustic- and optical-mode inversion in the phonon spectrum of certain metals became the first realistic example of noninteracting topological bosonic excitations in existing materials. However, the observable physical and ...

AMER PHYSICAL SOC2018

IR-induced conformational isomerization of a helical peptide in a cold ion trap

Thomas Rizzo, Annette Svendsen, Aleksandra Zabuga, Caroline Seaiby

In this work we use laser-induced population transfer techniques to study the conformational isomerization of a helical peptide, Ac-Phe-(Ala)5-LysH+, in a cold ion trap. In one scheme, called IR-UV hole-filling spectroscopy, a single conformation is select ...

American Institute of Physics2016

Nanoscale MOSFET Modeling for the Design of Low-power Analog and RF Circuits

Christian Enz, Alessandro Pezzotta

This paper presents the simplified charge-based EKV MOSFET model and shows that it can be used for advanced CMOS processes despite its very few parameters. The concept of inversion coefficient is then presented as an essential design parameter that spans t ...

IEEE2016

200 km fiber-loop Brillouin distributed fiber sensor using bipolar Golay codes and a three-tone probe

Luc Thévenaz, Marcelo Alfonso Soto Hernandez, Zhisheng Yang

Aiming at taking full advantage of bipolar codes, a method using a three-tone probe is proposed to alleviate the probe power limitation imposed by pump depletion in Golay-coded Brillouin distributed fiber sensors. Experimental results validate the techniqu ...

SPIE2015

Quantum state specific reactant preparation in a molecular beam by rapid adiabatic passage

Rainer Beck, Phil Morten Hundt, Helen Jane Chadwick, Maarten Eduard van Reijzen, Bruce Yoder

Highly efficient preparation of molecules in a specific rovibrationally excited state for gas/surface reactivity measurements is achieved in a molecular beam using tunable infrared (IR) radiation from a single mode continuous wave optical parametric oscill ...

American Institute of Physics2014

Surface-Plasmon-Induced Modification on the Spontaneous Emission Spectrum via Subwavelength-Confined Anisotropic Purcell Factor

Olivier Martin

The mechanism of using the anisotropic Purcell factor to control the spontaneous emission linewidths in a four-level atom is theoretically demonstrated; if the polarization angle bisector of the two dipole moments lies along the axis of large/small Purcell ...

American Chemical Society (ACS)2012

Development of Tunable Optical MEMS for Advanced Laser Beam Shaping, Homogenizing and Speckle Reduction

Jonathan Masson

In this thesis, the development, design, fabrication and characterization of three innovative laser beam shaping, homogenizing and speckle reduction devices are reported. Typical beam shaping devices are static and not easily adaptable to a large variety o ...

EPFL2012

Ultrafast Excited-State Dynamics of Rhenium(I) Photosensitizers [Re(Cl)(CO)(3)(N,N)] and [Re(imidazole)(CO)(3)(N,N)](+): Diimine Effects

Majed Chergui, Andrea Cannizzo, Olivier Christian Bräm, Amal El Nahhas, Cristina Consani

Femto- to picosecond excited-state dynamics of the complexes Re(L)(CO)(3)(N,N) (N,N = bpy, phen, 4,7-dimethyl-phen (dmp); L = Cl, n = 0; L = imidazole, n = 1+) were investigated using fluorescence up-conversion, transient absorption in the 650-285 nm ...

2011

Development of Ultraviolet Photon Echo Experiments for the Study of Molecular Dynamics in Solution

Ahmad Ajdar Zadeh Oskouei

This thesis work concerns the development and applications of ultrafast optical techniques and in particular photon echo in the UV range (< 300 nm). Development of these techniques in the UV range is important for studying molecular dynamics in solution, s ...

EPFL2011

Full-wave analysis of photonic-crystal structures with multi quantum well active region

Banafsheh Abasahl

In this paper, a semi-classical formulation for modeling photonic-crystal (PC) structures with a four-layer multi quantum well (MQW) active region is presented. The formulation treats the electromagnetic fields as a classical entity, while employing the qu ...

2010

Time-resolved x-ray absorption spectroscopy: Watching atoms dance

Majed Chergui, Wojciech Gawelda, Van Thai Pham, Amal El Nahhas, Renske Marjan van der Veen, Frederico Alves Lima

The introduction of pump-probe techniques to the field of x-ray absorption spectroscopy (XAS) has allowed the monitoring of both structural and electronic dynamics of disordered systems in the condensed phase with unprecedented accuracy, both in time and i ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2009

Photocurrent and photoconductance properties of a GaAs nanowire

Anna Fontcuberta i Morral

We report on photocurrent and photoconductance processes in a freely suspended p-doped single GaAs nanowire. The nanowires are grown by molecular beam epitaxy, and they are electrically contacted by a focused ion beam deposition technique. The observed pho ...

American Institute of Physics2009