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In this paper we report on the structure of van der Waals anthracene–argonn (n=1–6) clusters, which were interrogated by a complete set of experimental diagnoses based upon mass-selective, fragmentation-free, two-color, resonant two-photon ionization and laser induced fluorescence as well as a theoretical modeling of the ionization energy. We were able to provide a global assignment of the spectral features which rests on several independent sources of information: the spectral shifts δν and linewidths of the S1←S0 transition, the ionization energy shifts δI.E. and threshold widths and their comparison with the theoretical simulations, the hole-burning spectra, the structure-specific predissociation dynamics. The existence of two cluster ensembles, which present qualitatively different spectral features and significant relative intensity, has been evidenced for each cluster size. The first ensemble exhibits spectral features, typical of cold, rigid-like clusters. Only one prominent stable structure is found for each cluster size of this ensemble: (1|0) for n=1, (2|0) for n=2, (2|1) for n=3, (2|2) for n=4, (3|2) for n=5, (3|3) for n=6, where the notation (n-p|p) refers to the distribution of the argon atoms between the two molecular sides. The second ensemble has been assigned to more or less `hot' clusters having probably the same (n-p|p) arrangement as the first ones, but excited in high van der Waals vibrational levels through an intracluster vibrational relaxation of anthracene molecules. Results on similar heteroclusters reported in the literature are discussed on the light of our new assignment of the spectral features of small Ant–Arn clusters to structures differing by their internal energy content and not by their configuration.

In this paper, new experimental results using UV spectroscopy of the small benzene–Arn clusters are presented. We have found evidence for the vibrational predissociation of the S1 state of some of these species on a nanosecond time scale and we propose a new assignment for the UV spectral features of this system. This assignment is consistent with other experimental data and it accounts additionally for the previously reported spectral anomalies, in particular the ionization potential measurements of these species. The two-color R2PI spectra performed can thus be considered as nanosecond pump–probe experiments that allow us to estimate the relaxation rate of the S1state of these clusters. The vibrational relaxation is found to be strongly size and structure dependent: The two isomers [(1/1) and (2/0)] of the n=2 species exhibit different lifetimes differing by at least one order of magnitude. The size dependence of the relaxation process within the one-sided isomer series appears also paradoxical since th...

In this first application of double resonance multiphoton ionization photoelectron spectroscopy to study the higher excited states of a polyatomic molecule, we have obtained the double resonance absorption spectrum of chlorobenzene in the energy region 56000 to 66700 cm −1 . Three new band systems are identified as members of Rydberg series converging to the first ionization energy. These systems with the 0 0 0 bands at 63000, 64690 and 66390 cm − are tentatively assigned to the 3d, 4p and 4d Rydberg states, respectively.

From a rotational contour study of UV vibronic bands of the benzene—Ar 2 complex as well as from theoretical structures modelling, conclusive arguments are presented, demonstrating the existence of a second (2, 0) stable conformer of C s symmetry, in addition to the already known symmetric (1, 1) species.

Excitation and emission spectra of chlorine atoms isolated in neon matrices were studied in the VUV spectral range using synchrotron radiation. Spectra of the electronic transitions between the 2 P ground state and the first 2 P and 2 D excited states clearly show the existence of three different possible sites for the chlorine atom in a neon surrounding. by annealing, a rearrangement takes place so that only one site is left. The fine structure of the excitation and emission peaks shows the spin-orbit splittings of the electronic states with values very close to the gas phase.

Synchrotron radiation is used to excite selectively the chlorine molecule in a Ne buffer gas. Due to the fast relaxation induced by the buffer gas, in the excitation spectrum of the D′→A′ emission at 258 nm, a new progression is observed. It is attributed to the 3 1 Σ u + state which is the result of an avoided crossing between the Rydberg state π g →5pπ and the valence state (1441) (σ g →σ u ). It is characterized by T e =83251 cm −1 , ω e =783 cm −1 , ω e x e =29.6 cm −1 and r e =1.844 A.

We report the clear observation and assignment of the symmetric stretching and bending van der Waals modes in two three-bodyC 2v complexes, phenol- and aniline-(Ar)2, using resonant two-photon ionization.

The aim of this retrospective study was to report the results of a series of 218 laparoscopic resections for adenocarcinoma of the colon by the same surgical team over a 6-year period.Laparoscopic procedures included, for the right and the left colon, at first a ligature of the vascular pedicles, secondarily a dissection of the mesocolons, and were almost identical to the conventional procedures. A conversion to open laparotomy was necessary in 8.3% of the patients. Among 218 patients, there were 117 men and 101 women; the mean age was 69 years. Twenty nine per cent of the patients had already undergone open laparotomy. Mean ASA grade was 2.1. An emergency operation was necessary for 9% of the patients in relation with colonic obstruction (n = 20) or peritonitis (n = 3).Colonic resections were considered curative in 180 patients (82.6%). The mean duration of surgery was 157 minutes for the right colectomies and 148 for the left. The proportion of A, B, C, D Dukes stage tumours was respectively 19.3%, 38.5%, 27.5% and 14.7%. There was one post-operative death related to a serious epileptic seizure due to unknown cerebral metastases. The morbidity rate was 5.5% and the early reintervention rate 2.8%. There was no lost to follow-up. With a mean 35-month follow-up. 82.2% of the patients were alive after curative surgery. Abdominal wall recurrence at port sites occurred in four patients operated on for a Dukes C cancer before 1994. Prognosis was significantly dependent on cellular differentiation, lymph node extension, pericolic extension and Dukes stage. The 5-year actuarial survival rate, according to Kaplan-Meier method was 65.36%.Laparoscopic colon cancer resection was used by the authors in 92% of patients during 1997. The conversion rate to open laparotomy has been lower than 5% since 1995. Post-operative mortality was 0.4% and post-operative morbidity 5.5%. After curative colonic cancer resection, the 5-year actuarial survival rate was 65%.

The knowledge of the spectroscopy of the vibrational modes of the Van der Waals complexes is a key for the theoretical understanding and modelling of various physical processes occurring in these systems, e.g. intramolecular vibrational relaxation, unimolecular reaction dynamics leading to fragmentation, intersystem crossing, etc...

Synchrotron radiation is used to selectively excite the chlorine molecule in the VUV spectral range. Stationary fluorescence spectra of the 11Σu+ state are observed following primary excitation of 11Σu+ and 21Σu+. The bound-free part of the spectra is analysed with the aid of quantum mechanical computer simulations. A potential energy curve is constructed which is an approximation of the adiabatic double well potential energy curve of the 11Σu+ state. The inner well is characterized byTe=(73428±50) cm−1,re=(1.85 ± 0.05) A; for the outer well holdTe=(64631±50) cm−1,re=(2.57±0.05) A, ωe=(261±5) cm−1, ωexe=(0.668±0.01) cm−1 (35Cl2;v′

In a Cl2 + Rg doped neon matrix, the RgCl* and Rg2 Cl* excimers are not formed from a primary excitation of the free or complexed molecular chlorine. They are only observed when Cl atoms or RgCl van der Waals complexes preexist in the Ne matrix after photolysis of Cl2 . The XeCl* B1/2 and C3/2 states are shown to be nearly isoenergetic. The vibrational structure of the D1/2 state is resolved for the first time.

Time‐gated fluorescence spectra have been obtained in xenon excited by synchrotron radiation around the first resonance line. Evidence of the emission from the left turning point of the Xe2 excited Ou+ (3P1) potential curve is obtained between 2000 and 2100 A for different excitation wavelengths. From our results, we propose an experimental potential curve for the Ou+ state with an equilibrium distance Re of 3.25 A and a well depth De of 5000 cm−1. Franck–Condon factors have been calculated with this curve for the bound–free transitions between different vibrational levels of the Ou+ excited state and the Og+ ground state. They are in excellent agreement with experiment.

The Xe-Cl 2 van der Waals complex formed in a supersonic expansion is excited in a two-photon process. The XeCl(B,C) reaction spectra (excitation of the complex and detection of the XeCl (B→X) and (C→A) fluorescence) are obtained in the region 290–310 nm. In addition to a diffuse band also obtained in the C action spectrum, the B action spectrum presents a vibronic structure similar to the Xe-Cl (B←X) absorption band. Xe-Cl 2 ( 1 Π u ) resonantly enhanced two-photon process with two chromophores is proposed to account for the results.

The Xe-Cl2 van der Waals complex formed in a supersonic expansion is excited by a two-photon process at 297.5 nm. The XeCl∗ fragment obtained is vibrationally cold. This result is discussed and compared with those of the Xe∗ + Cl2 reaction and laser-assisted collision.

Synchrotron Radiation is used to selectively excite chlorine and Cl2 doped argon in the VUV region. Stationary fluorescence and excitation spectra of the 11Σu+, 21Σu+ and 23Πg Cl2* states and of the ArCl*(B−X) transition are obtained. The excitation threshold of ArCl*(B) in Ar/Cl2 system is found to be 1,285±5 A and that of ArCl(C) at ∼1,260 A. The formation of ArCl* and Cl*2(23Πg) is discussed in terms of recent potential curves data. A detailed time resolved study is reported which allows us to determine precisely the radiative lifetime of ArCl*(B) state (5.2 ns) and numerous kinetic parameters of this system, to estimate theC state energy and to discuss the relaxation and mixing process of the ArCl*(B) and (C) states. A two ladder multilevel kinetic model is described which accounts for the experimental results and shows the difficulty of studying this particular ArCl* system as compared to the closely related XeCl* and KrCl* ones.

UV fluorescence of pure Cl2 and Cl2/rare-gas mixtures has been investigated under selective, pulsed VUV excitation. In pure Cl2, a strong fluorescence between 1350 and 2000 A is found with typical radiative lifetimes of 3 ns. Addition of Kr(Ar) to Cl2 strongly quenches this fluorescence and let show up Kr(Ar)Cl* emissions as well as the Cl2 «laser» emission at 2580 A. The radiative lifetime of the Cl2 laser state is found to be 16 ns. Absorptions and emissions observed in this work are discussed in view of the results of time-resolved fluorescence spectroscopy and of recent theoretical results on the excited-potential curves of Cl2.

Synchrotron radiation at LURE has been used to excite xenon in the pressure range of 50 to 200 torr. The subsequent second continuum fluorescence at 1720 A has been spectrally and temporally analyzed. The observed two-component decay of this emission, as well as various spectral features, are shown to be in disagreement with some results previously reported in the literature.

Synchrotron radiation excitation and emission spectra with lifetime measurements are reported for the first time in the VUV region for systems consisting of Cl2 molecules trapped in a neon matrix, an argon matrix, and mixed Ar/Ne matrices. In pure neon, the emission spectrum of the D’→A’ ‘‘laser’’ transition at 4.7 eV of the Cl2 molecule is vibrationally well resolved and constitutes an interesting example of UV spectroscopy of a matrix ‘‘isolated’’ molecule. In pure argon or mixed Ar/Ne matrices, new broad emissions at 4.1, 3.8, and 3.5 eV are clearly identified, which result from the specific interaction between Cl*2 and Ar and are attributed to different charge–transfer states of the ArCl+Cl− entity. The Ar concentration dependence and the time‐gated spectra are shown to be especially useful in interpreting the large differences observed between the pure neon and the pure argon matrix case.

Monochromatic pulsed VUV excitation of Cl2 or inert gas atoms in Cl2 doped Kr and Ar leads to formation of KrCl* and ArCl*. The radiative lifetimes of the B states (KrCl* 19 ns, ArCl* 9 ns) and rate constants for excimer formation, quenching and collisional mixing of B and C states are given. The radiative lifetime and the quenching rate increase with vibrational excitation of the B state (KrCl*).

The de‐excitation of the 3P2, 3P1, and 1P1 states of argon was studied in pure argon between 10 and 200 torr and in Ar+CO and Ar+H2 mixtures. These states, which were followed by absorption spectroscopy, are populated after excitation of the gas by a short (20 ns) pulse of 500 keV electrons. The three body rate constants k2, which were not considered in previous low pressure studies, were measured for the two resonant states 3P1(k2=1.7×10−32 cm6 s−1) and 1P1 (k2=0.9×10−32 cm6 s−1). For the metastable 3P2, the measured value of k2 (1.6×10−32 cm6 s−1) is in good agreement with those found in the literature. However, our two body rate constant k1 for the 3P2 state is about ten times higher than values obtained previously from low pressure measurements. The rate constants for the quenching by CO and H2 were measured for the metastable state 3P2 (1.85 and 10.5×10−11 cm3 s−1) and for the resonant states 3P1 (4.5 and 20×10−11 cm3 s−1) and 1P1 (8.5 and 33×10−11 cm3 s−1).

Well-resolved absorption spectra of the B←X forbidden transition of the chlorobenzene cation have been obtained for the first time by two-photon induced dissociation of the ground state ion. The φ + fragment ions are detected with a time-of-flight mass spectrometer. The wavelength dependence of the fragment ion yield reflects the spectroscopy of the φCl + B intermediate state reached by the first photon. Chlorobenzene cations are formed by resonance-enhanced two-photon ionization (R2PI) process. B←X vibronic transitions are observed due to vibronic interactions between the nearby B and C states. A preliminary analysis of the spectra is proposed.

By means of pulsed electron beam excitation and kinetic absorption spectroscopy, rate coefficients for quenching the Ar 3P0,1,2 and 1P1 states by SF6 and N2 were found to range from 2.6 to 10 × 10−10 cm3/s, and 1.4 to 5.7 × 10−11 cm3/s, respectively. For the N2 measurements, ternary mixtures of Ar/SF6/N2 permitted us to study the role played by low energy electrons during the afterglow.

The postluminescence of N2(C 3Πu→ B 3Πg) induced by the transfer of energy to nitrogen by 3P2 metastable argon atoms obtained by the pulsed radiolysis of argon‐nitrogen mixtures has been studied spectrophoto‐electrically. The emission decay lifetime τ is controlled by the destruction of metastable argon atoms. The variation of 1/τ as a function of the argon or nitrogen pressure is used to determine the rate constants k1(Ar*+N2)=3± 0.3 × 10−11cm3sec−1 and k2(Ar*+2Ar)=6± 0.4 × 10−33cm6sec−1. The general reaction process is discussed. The results obtained seem to show that the metastables are formed mainly from the dissociative recombination of Ar2+ ions.

Le bombardement de gaz, CO2, CH4, CO a l'aide d'une source pulsee d'electrons de 600 keV fournissant 10 joules en 30 nanosecondes, a permis la mesure des durees de vie radiatives suivantes : CO+(A 2Πu) = 147 ± 10 ns ; CO+2(B 2Σ+u) = 135 ± 10 ns CH.(A 2Δ) = 800 ± 100 ns ; CO(C1Σ+) = 50 ± 10 ns.

The well‐resolved absorption spectrum of a large non‐radiative aromatic ion like chlorobenzene has been obtained by the method of resonance‐enhanced multiphoton dissociation (REMPDI). The cations are prepared in the ground electronic state with well‐defined rovibrational energy excess by resonace‐enhanced two‐photon ionization (R2PI). The light of a second laser excites the ions through a (1+1) process into predissociative states which dynamics has been first studied. The wavelength dependence of the fragment ion yield reflects the spectroscopy of the intermediate ionic state reached by the first photon. In this work, we present the completely vibrationally resolved spectrum of the B←X transition of φC1+. For the first time the rotational contour of the vibronic bands of R2PI‐prepared ions has been calculated. The comparison with the experimental band shapes has brought additional arguments for the assignment of the spectral features.

Recent work on the spectroscopic and photophysical properties of the excited states of Cl 2 trapped in an Ar matrix is compared with independent gas-phase results on chlorine or Cl 2 + rare gas as well as with other matrix studies. An alternative interpretation of the results is proposed.