We report the first use of synchrotron radiation, continuously tunable from 8 to 15 eV, for flame-sampling photoionization mass spectrometry (PIMS). Synchrotron radiation offers important advantages over pulsed vacuum ultraviolet lasers PIMS; these include superior signal-to-noise, soft ionization, and access photon energies outside limited tuning ranges current VUV laser sources. Near-threshold efficiency measurements were used determine absolute concentrations allene propyne isomers C3H4...

A flame-sampling molecular-beam photoionization mass spectrometer, recently designed and constructed for use with a synchrotron-radiation light source, provides significant improvements over previous spectrometers that have employed either electron-impact ionization or vacuum ultraviolet laser photoionization. These include superior signal-to-noise ratio, soft ionization, photon energies easily precisely tunable [E∕ΔE(FWHM)≈250–400] the 7.8–17-eV range required quantitative measurements of...

We studied the photoionization of 2-pyridone and its tautomer, 2-hydroxypyridine by means VUV synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. The efficiency (PIE) spectrum is composed steps. state energies [2-pyridone]+ cation in ground à excited electronic states, as well [2-hydroxypyridine]+ state, are determined. slow photoelectron spectra (SPES) dominated 000 transitions corresponding states together with several weaker bands population pure...

We present the design of a VMI spectrometer optimized for attosecond spectroscopy in 0–40 eV energy range. It is based on compact three-electrode configuration where lens shape, size, and material have been using numerical simulations to improve spectral resolution by factor ∼5 relative initial [Eppink Parker, Rev. Sci. Instrum. 68, 3477–3484 (1997)] while keeping flat response 10–40 The experimental performance tested an source high-order harmonic generation. A good agreement observed...

Imaging in real time the complete dynamics of a process as fundamental photoemission has long been out reach because difficulty combining attosecond temporal resolution with fine spectral and angular resolutions. Here, we achieve full decoding intricate angle-dependent helium, spectrally anisotropically structured by two-photon transitions through intermediate bound states. Using angularly resolved electron interferometry, characterize complex-valued transition probability amplitude toward...

This experimental work focuses on the complex autoionization dynamics of Ar(2) clusters below first ionization energy argon atom. is submitted to vacuum ultraviolet radiation, and photoelectron spectra are collected in coincidence with cluster ions. The revealed by dependence photon energy. We applied a new method which we developed analyze signal. Thus, were able (i) get complete vibrational progression Ar(2)(+) that was never observed up now, especially identifying 0-0 transition...

The ultrafast dynamics of copper tetraphenylporphyrin (CuTPP), octaethylporphyrin (CuOEP), and the free base (H2TPP), excited in S2 state have been investigated gas phase by femtosecond pump/probe experiments. porphyrins were Soret band at 400 nm. Strikingly, S2-S1 internal conversion H2TPP is very rapid (110 fs), as compared to that ZnTPP (600 previously observed. In turn, CuTPP CuOEP, S2, follow an efficient different relaxation pathway from other open-shell metalloporphyrins. These two...

Benzophenone is a prototype molecule for photochemistry in the triplet state through its high yield and reactivity.

The photoionization and photoelectron spectroscopy of He nanodroplets (${10}^{4}$ atoms) has been studied by imaging with photon energies from 22.5--24.5 eV. Total electron yield measurements reveal broad features, whose onset is $\ensuremath{\sim}1.5\text{ }\text{ }\mathrm{e}\mathrm{V}$ below the ionization potential atomic He. spectra are dominated very low energy electrons, $⟨{E}_{k}⟩$ less than 0.6 meV. These results attributed to formation autoionization highly vibrationally excited...

The gas-phase dynamics of two classes photochromic molecules, three spiropyrans and one spirooxazine, have been investigated here using both time-resolved mass spectrometry photoelectron spectroscopy approaches. It is, to our knowledge, the first experiment done these kinds molecules. molecules are excited at 266 nm probed 800 nm. comparison four has used propose a sequential photoisomerization mechanism involving steps occurring in 100 ps. Each is discussed related observed condensed-phase...

A systematic study of the ultrafast decay metalloporphyrins containing various transition metals with partially filled 3d shells and zinc (3d filled) is reported here after excitation in second excited state system (Soret band). Both time-of-flight mass spectrometry velocity map imaging have been used for detection. general biexponential a short time constant τ1∼100fs observed metal porphyrins, followed by τ2∼1ps decay. This evolution interpreted as porphyrin-to-metal charge transfer, τ1,...

The photoionization and photoelectron spectroscopy of pure He droplets were investigated at photon energies between 24.6 eV (the ionization energy He) 28.0 eV. Time-of-flight mass spectra images obtained a series molecular beam source temperatures pressures to assess the effect droplet size on dynamics. At below 16 K, where there is significant production clusters with more than 10(4) atoms, are dominated by fast electrons produced via direct ionization, small contribution from very slow...

Photoionization efficiency (PIE) curves for C(3) molecules produced by laser ablation are measured from 11.0 to 13.5 eV with tunable vacuum ultraviolet undulator radiation. A step in the PIE curve versus photon energy, obtained N(2) as carrier gas, supports conclusion of very effective cooling its linear (1)Sigma(g)(+) ground state. The second observed energy could be first experimental evidence C(3)(+)((2)Sigma(g)(+)) excited results, complemented ab initio calculations, suggest a...

The dynamics of the enolic form acetylacetone (E-AcAc) was investigated using a femtosecond pump−probe experiment. pump at 266 nm excited E-AcAc in first bright state, S2(ππ*). resulting probed by multiphoton ionization 800 nm. It for 80 ps on S2(ππ*) and S1(nπ*) potential energy surfaces. An important step is transfer from S2 to S1 that occurs with time constant 1.4 ± 0.2 ps. Before, system had left excitation region 70 10 fs. intermediate identified when traveled surface. Likely, it...

We studied the single photon ionization of gas phase adenine and cytosine by means vacuum ultraviolet synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. Both in-vacuum temperature-controlled oven aerosol thermodesorption were successfully applied promote intact neutral biological species into phase. The photoion yields are consistent with previous measurements. In addition, we deduced threshold photoelectron spectra slow for both species, where...

Biological entities, such as DNA bases or proteins, possess numerous tautomers and isomers that lie close in energy, making the experimental characterization of a unique tautomer challenging. We apply VUV synchrotron-based experiments combined with state-of-the-art ab initio methodology to determine adiabatic ionization energies (AIEs) specific gas-phase cytosine produced molecular beam. The structures energetics neutral cationic were determined using explicitly correlated methods. spectra...

Ba ( Ar ) ≈ 750 clusters were generated by associating the supersonic expansion and pick-up techniques. A femtosecond pump (266.3 nm)-probe (792 or 399.2 nm) experiment was performed to document dynamics of electronically excited barium within very multidimensional environment argon cluster. Barium in vicinity 6s9p P1 state probed ionization. The velocity imaging technique used monitor energy distribution photoelectrons photoions as a function delay time between probe pulses. complex...

We report on the vibronic structure of ground state X̃2A″ thymine cation, which has been measured using a threshold photoelectron photoion coincidence technique and vacuum ultraviolet synchrotron radiation. The spectrum, recorded over ∼0.7 eV above ionization potential (i.e., covering whole cation) shows rich vibrational that assigned with help calculated anharmonic modes electronic cation at PBE0/aug-cc-pVDZ level theory. adiabatic energy experimentally determined as AIE = 8.913 ± 0.005 eV,...

The S1(1ππ*) state of the (dominant) syn-conformer 2-chlorophenol (2-ClPhOH) in gas phase has a subpicosecond lifetime, whereas corresponding S1 states 3- and 4-ClPhOH have lifetimes that are, respectively, ∼2 ∼3-orders magnitude longer. A range experimental techniques–electronic spectroscopy, ultrafast time-resolved photoion photoelectron spectroscopies, H Rydberg atom photofragment translational velocity map imaging, Fourier transform infrared emission spectroscopy–as well as electronic...

Time-resolved photoion and photoelectron velocity mapped images from NO2 excited close to its first dissociation limit [to NO(X2Π) + O(3P2)] have been recorded in a two colour pump–probe experiment, using the frequency-doubled frequency-tripled output of regeneratively amplified titanium–sapphire laser. At least three processes are responsible for observed transient signals; negative signal (corresponding 266 nm pump), very short-lived cross-correlation pump probe pulses but on 400 side,...

Time-resolved dynamics of the photodissociation molecular oxygen, O2, via Σu−3 ion-pair state have been studied with femtosecond time resolution using a pump-probe scheme in combination velocity map imaging resulting O+ and O− ions. The fourth harmonic titanium-sapphire (Ti:sapphire) laser (λ≈205nm) was found to cause three-photon pumping O2 level at 18.1eV. parallel character observed images allowed us conclude that dissociation takes place on state. 815nm fundamental Ti:sapphire used as...

This work deals with the photophysics of a pyridinium betaine, 2-pyridin-1-yl-1H-benzimidazole (SBPa), based on combination steady-state, femtosecond photoionization (gas phase) and transient absorption (solution) spectroscopic measurements, supported by (LR)-PCM-(TD)DFT calculations. Preliminary new electrochemical results have revealed strongly negative solvatochromic charge transfer (CT) due to S0 → S2 vertical transition weakly-solvatochromic emission S1 transition. Advanced TDDFT...

How much time does it take for a wavepacket to roam on multidimensional potential energy surface? This combined theoretical and pump-probe femtosecond experiment 2-hydroxypyridine proposes an answer. Bypassing the well-established transition state conical intersection relaxation pathways, this molecular system undergoes into S1 excited state: central ring is destabilized by electronic excitation, within ~100 fs after absorption of pump photon, then H-atom bound oxygen roaming behavior when...

Direct measurements of Single vibronic Level InterSystem Crossing (SLISC) performed on the fluorenone molecule in gas phase, by time resolved photoelectron spectroscopy, revealed dramatic importance its structure intersystem crossing.