Search results for "two-photon [exchange]"

Confocal and Two-Photon Spectroscopy

2021

The spectroscopic analysis of bulk samples provides useful information at the mesoscopic scale that can be fostered when coupled with microscopy, which allows to integrate the spatial information in the analysis, this being of utmost importance for non‐homogeneous samples. Technologies such as confocal and two‐photon microscopy quickly became mainstream methods as they provide the possibility of noninvasive real‐time analysis of specimens of different nature, eliciting specific features even in samples with non‐ergodic behaviour. The spatial resolution of optical microscopy has its roots in the diffraction of light on the objective lens of the imaging system. Fluorescence microscopy is an o…

Infrared to visible upconversion luminescence properties in the system Ln2BaZnO5 (Ln=La, Gd)

2009

Abstract We have investigated the upconversion properties of the rare-earth doped systems La 2 BaZnO 5 ( I 4/ mcm ) and Gd 2 BaZnO 5 ( Pbnm ). The dependence of the luminescence properties on the identity and the concentration of the dopants, Er 3+ and Er 3+ co-doped with Yb 3+ , as well as on the synthetic route, was examined. Following coherent excitation at 975 nm, strong upconversion emission was observed in the visible region (525, 550 and 660 nm). Power dependence studies revealed a two photon process for these emissions. In the co-doped samples, a blue emission (410 nm) could also be observed. For this emission, the power dependence studies confirmed a three photon process.

Size-And Wavelength-Dependent Two-Photon Absorption Cross-Section of CsPbBr3 Perovskite Quantum Dots

2017

All-inorganic colloidal perovskite quantum dots (QDs) based on cesium, lead, and halide have recently emerged as promising light emitting materials. CsPbBr3 QDs have also been demonstrated as stable two-photon-pumped lasing medium. However, the reported two photon absorption (TPA) cross sections for these QDs differ by an order of magnitude. Here we present an in-depth study of the TPA properties of CsPbBr3 QDs with mean size ranging from 4.6 to 11.4 nm. By using femtosecond transient absorption (TA) spectroscopy we found that TPA cross section is proportional to the linear one photon absorption. The TPA cross section follows a power law dependence on QDs size with exponent 3.3 +- 0.2. The …

Dispersion relation formalism for the two-photon exchange correction to elastic muon-proton scattering: elastic intermediate state

2018

We evaluate the two-photon exchange correction to the unpolarized cross section in the elastic muon-proton scattering within dispersion relations. One of the six independent invariant amplitudes requires a subtraction. We fix the subtraction function to the model estimate of the full two-photon exchange at one of three MUSE beam energies and make a prediction for the two other energies. Additionally, we present single and double polarization observables accounting for the lepton mass.

Absolute frequency measurement of rubidium 5S-7S two-photon transitions.

2013

We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with a cw laser digitally locked to an atomic transition and referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising candidate for frequency reference. The performed tests yield the transition frequency with accuracy better than reported previously.

Collinear two-photon excitation of indium rydberg states in a fast atomic beam

1986

The 29p-Rydberg state of neutral indium was produced by double resonant two-photon excitation in a fast atomic beam and detected via field ionization in a longitudinal electric field.

Two-photon microscopy and neuroinflammation: Crosstalk between T cells and neurons

2014

Intensity Invariance of Strong-Field Two-Photon Absorption

2010

We demonstrate experimentally and theoretically the intensity-invariant scaling formula of coherent control of two-photon absorption as a function of pulse-shape parameters of ultrafast laser field in the strong-interaction regime.

Dominance of the first excitation step for magnetic circular dichroism in near-threshold two-photon photoemission

2012

Magnetic circular dichroism (MCD) in near-threshold photoemission is measured for a perpendicularly magnetized Cs/Co/Pt(111) film with work function adjusted by Cs adsorption. For one-photon photoe ...

Quasi-isotropic 3-D resolution in two-photon scanning microscopy.

2009

One of the main challenges in three-dimensional microscopy is to overcome the lack of isotropy of the spatial resolution, which results from the axially-elongated shape of the point spread function. Such anisotropy gives rise to images in which significant axially-oriented structures of the sample are not resolved. In this paper we achieve an important improvement in z resolution in two-photon excitation microscopy through spatial modulation of the incident beam. Specifically, we demonstrate that the design and implementation of a simple shaded ring performs quasi-isotropic three-dimensional imaging and that the corresponding loss in luminosity can be easily compensated by most available fe…