Enhanced absorption Hanle effect on the Fg=F->Fe=F+1 closed transitions

We analyse the Hanle effect on a closed $F_g\to F_e=F_g+1$ transition. Two configurations are examined, for linear- and circular-polarized laser radiation, with the applied magnetic field collinear to the laser light wavevector. We describe the peculiarities of the Hanle signal for linearly-polarized laser excitation, characterized by narrow bright resonances at low laser intensities. The mechanism behind this effect is identified, and numerical solutions for the optical Bloch equations are presented for different transitions.Comment: to be published in J. Opt. B, special issue on Quantum Coherence and Entanglement (February 2001

Quantum cascade laser based hybrid dual comb spectrometer

Four-wave-mixing-based quantum cascade laser frequency combs (QCL-FC) are a powerful photonic tool, driving a recent revolution in major molecular fingerprint regions, i.e. mid- and far-infrared domains. Their compact and frequency-agile design, together with their high optical power and spectral purity, promise to deliver an all-in-one source for the most challenging spectroscopic applications. Here, we demonstrate a metrological-grade hybrid dual comb spectrometer, combining the advantages of a THz QCL-FC with the accuracy and absolute frequency referencing provided by a free-standing, optically-rectified THz frequency comb. A proof-of-principle application to methanol molecular transitions is presented. The multi-heterodyne molecular spectra retrieved provide state-of-the-art results in line-center determination, achieving the same precision as currently available molecular databases. The devised setup provides a solid platform for a new generation of THz spectrometers, paving the way to more refined and sophisticated systems exploiting full phase control of QCL-FCs, or Doppler-free spectroscopic schemes

Alternative approach to the optimality of the threshold strategy for spectrally negative Levy processes

Consider the optimal dividend problem for an insurance company whose uncontrolled surplus precess evolves as a spectrally negative Levy process. We assume that dividends are paid to the shareholders according to admissible strategies whose dividend rate is bounded by a constant. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. Kyprianou, Loeffen and Perez [28] have shown that a refraction strategy (also called threshold strategy) forms an optimal strategy under the condition that the Levy measure has a completely monotone density. In this paper, we propose an alternative approach to this optimal problem.Comment: 16 page

Étude de l'effet stark dans les raies de résonance du sodium par une méthode de jet atomique

The atomic beam method previously used at Berkeley for other alkalis, has been applied to the study of the Stark effect in the resonance lines of sodium. The values of the electric polarizabilities of the 3 2P1/2 and 3 2P3/2 levels are deduced : α(3 2P 1/2) = 50,5(5) × 10-24 cm3 ; α (3 2P 3/2, MJ = ∓ 1/2) = 67(8) × 10-24 cm3 ; α (3 2P 3/2, MJ = ∓ 3/2) = 37,5(4) × 10-24 cm3. These results are compared with theoretically determined values.La méthode de jet atomique précédemment utilisée à Berkeley pour d'autres alcalins, est appliquée à l'étude de l'effet Stark dans les raies de résonance du sodium. On en déduit les valeurs des polarisabilités électriques des niveaux 3 2P 1/2 et 3 2P3/2 : α(3 2P 1/2) = 50,5(5) × 10-24 cm3 ; α (3 2P 3/2, MJ = ∓ 1/2) = 67(8) × 10-24 cm3 ; α (3 2P 3/2, MJ = ∓ 3/2) = 37,5(4) × 10-24 cm3. Ces résultats sont comparés à des déterminations théoriques

12C16O2 line intensities around 1.6 µm with a precision better than 0.5 percent. Affiche

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12^{12}C16^{16}O2_2 LINE INTENSITIES AROUND 1.6 μ\mum WITH A PRECISION BETTER THAN 0.5 PERCENT

Author Institution: Laboratoire de Recherche sur la Physico-Chimie des Surfaces et Interfaces, Universite de Skikda,; BP 26, Skikda 21000, Algeria; Laboratoire de Physique Moleculaire et Applications, CNRS, case courrier 76,; Universite Pierre-et-Marie-Curie, 75252 Paris Cedex 05, France; Groupe de Spectrometrie Moleculaire et Atmospherique, CNRS, UMR 6089,; Universite de Reims-Champagne-Ardenne, Faculte des Sciences, BP 1039, 51687 Reims Cedex 2, France; Laboratoire de Photophysique Moleculaire, Unite Propre du C.N.R.S., Batiment 350,; Universite de Paris-Sud, 91405 Orsay, France, email: [email protected]\maketitle Using Fourier transform spectra (FTS) and a multispectrum fitting procedure, 395 absolute lineintensities of $^{12}$C$^{16}$O$_2$ have been measured}$C$^{16}$O$_2$line intensity measurements around 1.6$\mum, Journal of Molecular Spectroscopy, in press (2006).} between 6035 and 6950 cm^{-1}, for the 4 cold bands 30014-00001, 30013-00001, 30012-00001, and 30011-00001, and for the 3 hot bands 31113-01101, 31112-01101, and 01131-01101. Vibrational transition dipole moments and Herman-Wallis coefficients are reported for each band. Comparisons are made with previous experimental results and with data available in the HITRAN database and the Carbon Dioxide Spectroscopic Databank (CDSD).\\ Comparisons with experimental line intensities recently obtained} from FTS for the 2 bands 30013-00001 and 30012-00001 are also performed. They show a very good line by line agreement: (0.3 \pm$0.6)$\%$on the mean for a hundred of lines, with a maximum discrepancy 1.6$\%$. Thus, the accuracy of these sets of individual line intensities, which was originally estimated about 3$\%$on the average in both works, is likely better than 1$\%$. This is close to what is needed by some atmospheric experiments, as OCO