Search results for "Laser Spectroscopy"
showing 10 items of 151 documents
Intramolecular charge transfer and dual fluorescence of 4-(dimethylamino)benzonitrile: ultrafast branching followed by a two-fold decay mechanism.
2011
International audience; In this contribution we present new experimental and theoretical results for the intramolecular charge transfer (ICT) reaction underlying the dual fluorescence of 4-(dimethylamino) benzonitrile ( DMABN), which indicate that the fully twisted ICT (TICT) state is responsible for the time-resolved transient absorption spectrum while a distinct partially twisted ICT (pTICT) structure is suggested for the fluorescent ICT state.
Precision Measurement of the First Ionization Potential of Nobelium
2018
One of the most important atomic properties governing an element's chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626 21±0.000 05 eV. This work provides a stringent benchmark for st…
High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED
2017
Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron–nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improve…
Transient absorption studies of the Ru(dcbpy)2(NCS)2 excited state and the dye cation on nanocrystalline TiO2 film
2001
We have measured dynamics of the Ru(dcbpy)2(NCS)2 [dcbpy = 4,4′-dicarboxy-2,2′-bipyridine] excited state and the dye cation on nanocrystalline TiO2 film in the wavelength region 700–900 nm. The dye in ethanol solution and Ru(dcbpy)2(NCS)2 sensitized nanocrystalline Al2O3 films were used as non-injecting reference samples for excited state identification. For TiO2/Ru(dcbpy)2(NCS)2 film the `reactant' decay and `product' formation kinetics observed at different probe wavelengths showed that the resolved transient absorption picosecond components (1.1±0.2), (12±2) and (100±5) ps are related to electron injection from the excited states of the dye to the semiconductor TiO2.
Photoinduced interfacial electron injection in RuN3–TiO2 thin films: Resolving picosecond timescale injection from the triplet state of the protonate…
2008
Using femtosecond transient absorption spectroscopy we have studied light-induced electron injection from the sensitizer RuN3 and its partly deprotonated tetrabutylamonium salt to nano-structured TiO2 film. Previous studies have suggested significant differences in electron injection dynamics for these dyes and some results have indicated that aggregation of the sensitizer may lead to slow injection. By measuring transient absorption spectra and kinetics of RuN3 and RuN3-TBA in solution and attached to TiO2 film we show that the electron injection dynamics are very similar for the two forms of the dye and that aggregation has only moderate effects on the electron transfer dynamics. (c) 2008…
Transient and near‐edge absorption in YVO 4 crystals
2007
The process of near-edge absorption annealing in air was studied up to 1500C in YVO4. In this annealing process, two stages with activation energies of 0.16 eV and 0.38 eV were obtained. (Should combine to make this one paragraph)In addition to the annealing study, the transient absorption induced by pulsed electron beam excitation (270 keV, 8 ns) was completed on a set of YVO4 samples with different near-edge absorption levels in the spectral region 3.2-3.5 eV. The spectral range from ∼1.25 eV up to 3.0 eV is covered by strong transient absorption. Transient absorption spectra show at least three broad overlapping bands (∼1.3 eV, ∼2.0 eV and ∼3.0 eV). The 3 eV peak position is close to the…
Production of neutron deficient rare isotope beams at IGISOL; on-line and off-line studies
2004
This article reports on recent on-line yield measurements employing the light-ion and heavy-ion reaction-based ion guide systems and new results on a-recoil ion transport properties in ion guides with and without electric fields. In addition, the presently used ion guide designs for fusion evaporation reactions are introduced. The present study investigated different schemes for ion extraction from the gas cell. The addition of an extra ring electrode between the traditional skimmer electrode and the exit hole led to transmission independent of the primary beam intensity as opposed to strong intensity dependence observed earlier with the plain skimmer only. Furthermore, the mass resolving p…
Amplifier similariton fiber laser with nonlinear spectral compression
2012
International audience; We propose a new concept of a fiber laser architecture supporting self-similar pulse evolution in the amplifier and nonlinear spectral pulse compression in the passive fiber. The latter process allows for transform-limited picosecond pulse generation, and improves the laser's power efficiency by preventing strong spectral filtering from being highly dissipative. Aside from laser technology, the proposed scheme opens new possibilities for studying nonlinear dynamical processes. As an example, we demonstrate a clear period-doubling route to chaos in such nonlinear laser system.
High Yield Ultrafast Intramolecular Singlet Exciton Fission in a Quinoidal Bithiophene
2015
We report the process of singlet exciton fission with high-yield upon photoexcitation of a quinoidal thiophene molecule. Efficient ultrafast triplet photogeneration and its yield are determined by photoinduced triplet-triplet absorption, flash photolysis triplet lifetime measurements, as well as by femtosecond time-resolved transient absorption and fluorescence methods. These experiments show that optically excited quinoidal bithiophene molecule undergoes ultrafast formation of the triplet-like state with the lifetime ∼57 μs. CASPT2 and RAS-SF calculations have been performed to support the experimental findings. To date, high singlet fission rates have been reported for crystalline and pol…
Complexation and Electronic Communication between Corannulene-Based Buckybowls and a Curved Truxene-TTF Donor
2017
Abstract: The association behavior of an electron-donating, bowl-shaped, truxene-based tetrathiafulvalene (truxTTF) with two corannulene-based fullerene fragments, C32H12 and C38H14, is investigated in several solvents. Formation of 1:1 complexes is followed by absorption titrations and complemented by density functional theory (DFT) calculations. The binding constants are in the range logKa=2.9–3.5. DFT calculations reveal that the most stable arrangement is the conformation in which the 1,3-dithiole ring of truxTTF is placed inside the concave cavity of the corannulene derivative. This arrangement is confirmed experimentally by NMR measurements, and implies that a combination of p–p and C…