Search results for " SPECT"

Photodynamics studies of ligand-protected gold nanoclusters by using ultrafast transient infrared spectroscopy

2015

Highly monodisperse samples of three ligand-protected gold nanoclusters Au102(pMBA)44, Au144(SC2H4Ph)60, and a cluster tentatively identified as Au130(pMBA)50, were characterized by UV/vis and infrared spectroscopy, and their photodynamics was studied by transient absorption spectroscopy. The dynamics study for each cluster was performed by electronically exciting the cluster with a pump pulse in the visible or near infrared region and by monitoring the transient absorption of vibrational modes of the ligands with a mid-IR probe pulse. The photodynamics studies were used to determine the molecular or metallic behavior of the cluster, and also to gain important size dependent information abo…

Silk-Water: a dynamic duo

2010

Ultrafast Coherent THz Lattice Dynamics Coupled to Spins in the van der Waals Antiferromagnet FePS3

2022

Coherent THz optical lattice and hybridized phonon–magnon modes are triggered by femtosecond laser pulses in the antiferromagnetic van der Waals semiconductor FePS3. The laser-driven lattice and spin dynamics are investigated in a bulk crystal as well as in a 380 nm-thick exfoliated flake as a function of the excitation photon energy, sample temperature and applied magnetic field. The pump-probe magneto-optical measurements reveal that the amplitude of a coherent phonon mode oscillating at 3.2 THz decreases as the sample is heated up to the Néel temperature. This signal eventually vanishes as the phase transition to the paramagnetic phase occurs, thus revealing its connection to the long-ra…

Pseudospectrum of Reissner-Nordström black holes: Quasinormal mode instability and universality

2021

Black hole spectroscopy is a powerful tool to probe the Kerr nature of astrophysical compact objects and their environment. The observation of multiple ringdown modes in gravitational waveforms could soon lead to high-precision gravitational spectroscopy, so it is critical to understand if the quasinormal mode spectrum is stable against perturbations. It was recently shown that the pseudospectrum can shed light on the spectral stability of black hole quasinormal modes. We study the pseudospectrum of Reissner-Nordstr\"om spacetimes and we find a spectral instability of scalar and gravitoelectric quasinormal modes in subextremal and extremal black holes, extending similar findings for the Sch…

Coronal properties of active G-type stars in different evolutionary phases

2005

We report on the analysis of XMM-Newton observations of three G-type stars in very different evolutionary phases: the "weak-line" T Tauri star HD 283572, the Zero Age Main Sequence star EK Dra and the Hertzsprung-gap giant star 31 Corn. The X-ray luminosities of the three stars are all in the range 10(30) - 10(31) erg/s. We compare the Emission Measure Distributions of these bright sources, derived from high-resolution X-ray spectra, as well as the pattern of elemental abundances vs. First Ionization Potential (FIP). The results of our analysis suggest that the coronae of these stars are very similar in terms of dominant coronal magnetic structures, in spite of differences in their evolutio…

Spectral analysis of the dipping LMXB system XB 1916-053

2019

Context: XB 1916-053 is a low mass X-ray binary system (LMXB) hosting a neutron star (NS) and showing periodic dips. The spectrum of the persistent emission was modeled with a blackbody component having a temperature between 1.31 and 1.67 keV and with a Comptonization component with an electron temperature of 9.4 keV and a photon index $\Gamma$ between 2.5 and 2.9. The presence of absorption features associated with highly ionized elements suggested the presence of partially ionized plasma in the system. Aims: In this work we performed a study of the spectrum of XB 1916-053, which aims to shed light on the nature of the seed photons that contribute to the Comptonization component. Methods: …

Spin Crossover and Long-Lived Excited States in a Reduced Molecular Ruby.

2020

Abstract The chromium(III) complex [CrIII(ddpd)2]3+ (molecular ruby; ddpd=N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) is reduced to the genuine chromium(II) complex [CrII(ddpd)2]2+ with d4 electron configuration. This reduced molecular ruby represents one of the very few chromium(II) complexes showing spin crossover (SCO). The reversible SCO is gradual with T 1/2 around room temperature. The low‐spin and high‐spin chromium(II) isomers exhibit distinct spectroscopic and structural properties (UV/Vis/NIR, IR, EPR spectroscopies, single‐crystal XRD). Excitation of [CrII(ddpd)2]2+ with UV light at 20 and 290 K generates electronically excited states with microsecond lifetimes. This…

Data set: Towards a rapid screening of liver grafts at the operating room using mid-infrared spectroscopy

2020

The estimation of steatosis in a liver graft is mandatory prior to liver transplantation, as the risk of graft failure increases with the level of infiltrated fat. However, the assessment of liver steatosis before transplantation is typically based on a qualitative or semi-quantitative characterization by visual inspection and palpation, and histological analysis. Thus, there is an unmet need for transplantation surgeons to have access to a diagnostic tool enabling an in situ fast classification of grafts prior extraction. In this study, we have assessed an Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopic method compatible with the requirements of an operation…

Data set: Towards a rapid screening of liver grafts at the operating room using mid-infrared spectroscopy

2020

The estimation of steatosis in a liver graft is mandatory prior to liver transplantation, as the risk of graft failure increases with the level of infiltrated fat. However, the assessment of liver steatosis before transplantation is typically based on a qualitative or semi-quantitative characterization by visual inspection and palpation, and histological analysis. Thus, there is an unmet need for transplantation surgeons to have access to a diagnostic tool enabling an in situ fast classification of grafts prior extraction. In this study, we have assessed an Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopic method compatible with the requirements of an operation…

Data set: Towards a rapid screening of liver grafts at the operating room using mid-infrared spectroscopy

2020

The estimation of steatosis in a liver graft is mandatory prior to liver transplantation, as the risk of graft failure increases with the level of infiltrated fat. However, the assessment of liver steatosis before transplantation is typically based on a qualitative or semi-quantitative characterization by visual inspection and palpation, and histological analysis. Thus, there is an unmet need for transplantation surgeons to have access to a diagnostic tool enabling an in situ fast classification of grafts prior extraction. In this study, we have assessed an Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopic method compatible with the requirements of an operation…