Olivier Allard - Academia.edu (original) (raw)

Papers by Olivier Allard

W. D. Knight, K. Clemenger, W. A. de Heer, W. A. Saunders, M. Y. Chou, and M. L. Cohen Phys. Rev.... more W. D. Knight, K. Clemenger, W. A. de Heer, W. A. Saunders, M. Y. Chou, and M. L. Cohen Phys. Rev. Lett.

Author Institution: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austri... more Author Institution: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria/EU

Environment and Planning B: Urban Analytics and City Science

est docteur en physique de l'université d'Hanovre et de Paris-Sud. Il dispose de plus de 7 années... more est docteur en physique de l'université d'Hanovre et de Paris-Sud. Il dispose de plus de 7 années d'expérience de la recherche scientifique dans des laboratoires européens en France, Allemagne et Autriche. Ses recherches portaient sur les interactions atomiques et moléculaires, les nanosciences et l'optique quantique. Il est l'auteur d'une douzaine de publications scientifiques et a participé à une vingtaine de conférences internationales.

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C10 at the 1S+1S calcium dimer asymptote are determined... more The van der Waals coefficients C6, C8 and C10 at the 1S+1S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X 1Sigmamathrmg+^1\Sigma_{\mathrm g}^{+}1Sigmamathrmg+ ground state reaching v”=38. That level which is only 0.2 cm-1 below the molecular 1S+1S asymptote has an outer classical turning point of about 20 Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

The filtered laser excitation technique was applied for measuring transition frequencies of the C... more The filtered laser excitation technique was applied for measuring transition frequencies of the Ca$_2$ B-X system from asymptotic levels of the X$^1\Sigma_{\mathrm g}^{+}$ ground state reaching v′′=38v''=38v′′=38. That level has an outer classical turning point of about 20~\AA which is only 0.2 \rcm below the molecular 1^11S$+^1$S asymptote. Extensive analysis of the spectroscopic data, involving Monte Carlo simulation, allowed for a purely experimental determination of the long range parameters of the potential energy curve. The possible values of the s-wave scattering length could be limited to be between 250$a_0$ and 1000$a_0$.

European Physical Journal D, 2005

The coupled states A1Σu+ (1D + 1S), c3Πu (3P + 1S) and a3Σu+ (3P + 1S) of the calcium dimer are i... more The coupled states A1Σu+ (1D + 1S), c3Πu (3P + 1S) and a3Σu+ (3P + 1S) of the calcium dimer are investigated in a laser induced fluorescence experiment combined with high-resolution Fourier-transform spectroscopy. A coupled state analysis of the observed levels, considering a potential model, which is complete within the subspace of relevant neighboring states, is performed using the Fourier Grid Hamiltonian method. We determine the potential energy curve of the A1Σu+ and c3Πu states and the strengths of the couplings between them. The c3Πu and a3Σu+ states are of particular importance for the description of collisional processes between calcium atoms in the ground state 1S0 and excited state 3P1 applied in studies for establishing an optical frequency standard with Ca.

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C{10} at the ^1S+^1S calcium dimer asymptote are determ... more The van der Waals coefficients C6, C8 and C{10} at the ^1S+^1S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X^1Σ_g+ ground state reaching v''=38. That level which is only 0.2 cm^{-1} below the molecular ^1S+^1S asymptote has an outer classical turning point of about 20 Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

Journal of Physics B-atomic Molecular and Optical Physics, 2011

We report the recording of new highly resolved Fourier transform spectra of the neutral praseodym... more We report the recording of new highly resolved Fourier transform spectra of the neutral praseodymium atom. With the help of the new spectra we found about 9000 new lines from which—in the region 3260 to 9880 Å—1194 could be classified as transitions between energy levels of the Pr atom and 19 as transitions of the Pr ion. Twenty-three new atomic energy levels of odd parity and one of even parity were discovered during this first examination. The spectra might be very helpful for further laser spectroscopic investigations of the hyperfine structure of Pr I and Pr II transitions.

Physical Review A, 2002

The B 1Sigma+u-->X 1Sigma+g system in 40Ca2 was studied by Fourier-transform spectrosc... more The B 1Sigma+u-->X 1Sigma+g system in 40Ca2 was studied by Fourier-transform spectroscopy. Transitions to 730 ground-state levels were induced by the blue-green lines of an Ar+ radiation and the single-mode radiation of a frequency-doubled continuous-wave Nd:YAG yttrium aluminum garnet laser. An accurate potential-energy curve, which covers 99.8% of the well depth, was derived directly from the experimentally observed differences between

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C10 at the 1 S+ 1 S calcium dimer asymptote are determi... more The van der Waals coefficients C6, C8 and C10 at the 1 S+ 1 S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X 1 Σ + g ground state reaching v = 38. That level which is only 0.2 cm −1 below the molecular 1 S+ 1 S asymptote has an outer classical turning point of about 20Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

Physical Review Letters, 2008

The electronic excitation spectra of all possible homo-and heteronuclear high-spin (quartet) trim... more The electronic excitation spectra of all possible homo-and heteronuclear high-spin (quartet) trimers of K and Rb (K x Rb 3ÿx , x 0 . . . 3) assembled on the surface of superfluid helium droplets, are measured in the spectral range from 10 600 to 17 400 cm ÿ1 . A regular series of corresponding bands is observed, reflecting the similar electronic structure of all these trimers. For the assignment and separation of overlapping bands, we determine x directly, with mass-selected beam depletion, and indirectly with a V-type double-resonance scheme. The assignment is confirmed by high-level ab initio calculations of the electronic structure of the bare trimers. The level structure is rationalized in terms of harmonic-oscillator states of the three valence electrons in a quantum-dot-like confining potential. We predict that three should be a magic number for high-spin alkali clusters.

Journal of Physics B-atomic Molecular and Optical Physics, 2006

ABSTRACT KRb and Rb2 dimers are formed on cold helium nanodroplets. Laser excitation and emission... more ABSTRACT KRb and Rb2 dimers are formed on cold helium nanodroplets. Laser excitation and emission spectra from the transition (1)3Πg–3Σu+ of Rb2 and the transition (2)3Π–3Σ+ of KRb have been measured. A thorough analysis of the emission, which takes place after desorption of the dimers from the surface of the helium cluster, has been performed. It allows us to determine the redistribution of vibrational population on the droplet surface. A comparison of the experimental spectra with simulations, obtained with the potential energy curves and dipole moments calculated by Aymar and Dulieu, allows a test of the accuracy of the ab initio potentials.

W. D. Knight, K. Clemenger, W. A. de Heer, W. A. Saunders, M. Y. Chou, and M. L. Cohen Phys. Rev.... more W. D. Knight, K. Clemenger, W. A. de Heer, W. A. Saunders, M. Y. Chou, and M. L. Cohen Phys. Rev. Lett.

Author Institution: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austri... more Author Institution: Institute of Experimental Physics, TU Graz, Petersgasse 16, 8010 Graz, Austria/EU

Environment and Planning B: Urban Analytics and City Science

est docteur en physique de l'université d'Hanovre et de Paris-Sud. Il dispose de plus de 7 années... more est docteur en physique de l'université d'Hanovre et de Paris-Sud. Il dispose de plus de 7 années d'expérience de la recherche scientifique dans des laboratoires européens en France, Allemagne et Autriche. Ses recherches portaient sur les interactions atomiques et moléculaires, les nanosciences et l'optique quantique. Il est l'auteur d'une douzaine de publications scientifiques et a participé à une vingtaine de conférences internationales.

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C10 at the 1S+1S calcium dimer asymptote are determined... more The van der Waals coefficients C6, C8 and C10 at the 1S+1S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X 1Sigmamathrmg+^1\Sigma_{\mathrm g}^{+}1Sigmamathrmg+ ground state reaching v”=38. That level which is only 0.2 cm-1 below the molecular 1S+1S asymptote has an outer classical turning point of about 20 Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

The filtered laser excitation technique was applied for measuring transition frequencies of the C... more The filtered laser excitation technique was applied for measuring transition frequencies of the Ca$_2$ B-X system from asymptotic levels of the X$^1\Sigma_{\mathrm g}^{+}$ ground state reaching v′′=38v''=38v′′=38. That level has an outer classical turning point of about 20~\AA which is only 0.2 \rcm below the molecular 1^11S$+^1$S asymptote. Extensive analysis of the spectroscopic data, involving Monte Carlo simulation, allowed for a purely experimental determination of the long range parameters of the potential energy curve. The possible values of the s-wave scattering length could be limited to be between 250$a_0$ and 1000$a_0$.

European Physical Journal D, 2005

The coupled states A1Σu+ (1D + 1S), c3Πu (3P + 1S) and a3Σu+ (3P + 1S) of the calcium dimer are i... more The coupled states A1Σu+ (1D + 1S), c3Πu (3P + 1S) and a3Σu+ (3P + 1S) of the calcium dimer are investigated in a laser induced fluorescence experiment combined with high-resolution Fourier-transform spectroscopy. A coupled state analysis of the observed levels, considering a potential model, which is complete within the subspace of relevant neighboring states, is performed using the Fourier Grid Hamiltonian method. We determine the potential energy curve of the A1Σu+ and c3Πu states and the strengths of the couplings between them. The c3Πu and a3Σu+ states are of particular importance for the description of collisional processes between calcium atoms in the ground state 1S0 and excited state 3P1 applied in studies for establishing an optical frequency standard with Ca.

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C{10} at the ^1S+^1S calcium dimer asymptote are determ... more The van der Waals coefficients C6, C8 and C{10} at the ^1S+^1S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X^1Σ_g+ ground state reaching v''=38. That level which is only 0.2 cm^{-1} below the molecular ^1S+^1S asymptote has an outer classical turning point of about 20 Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

Journal of Physics B-atomic Molecular and Optical Physics, 2011

We report the recording of new highly resolved Fourier transform spectra of the neutral praseodym... more We report the recording of new highly resolved Fourier transform spectra of the neutral praseodymium atom. With the help of the new spectra we found about 9000 new lines from which—in the region 3260 to 9880 Å—1194 could be classified as transitions between energy levels of the Pr atom and 19 as transitions of the Pr ion. Twenty-three new atomic energy levels of odd parity and one of even parity were discovered during this first examination. The spectra might be very helpful for further laser spectroscopic investigations of the hyperfine structure of Pr I and Pr II transitions.

Physical Review A, 2002

The B 1Sigma+u-->X 1Sigma+g system in 40Ca2 was studied by Fourier-transform spectrosc... more The B 1Sigma+u-->X 1Sigma+g system in 40Ca2 was studied by Fourier-transform spectroscopy. Transitions to 730 ground-state levels were induced by the blue-green lines of an Ar+ radiation and the single-mode radiation of a frequency-doubled continuous-wave Nd:YAG yttrium aluminum garnet laser. An accurate potential-energy curve, which covers 99.8% of the well depth, was derived directly from the experimentally observed differences between

European Physical Journal D, 2003

The van der Waals coefficients C6, C8 and C10 at the 1 S+ 1 S calcium dimer asymptote are determi... more The van der Waals coefficients C6, C8 and C10 at the 1 S+ 1 S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X 1 Σ + g ground state reaching v = 38. That level which is only 0.2 cm −1 below the molecular 1 S+ 1 S asymptote has an outer classical turning point of about 20Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.

Physical Review Letters, 2008

The electronic excitation spectra of all possible homo-and heteronuclear high-spin (quartet) trim... more The electronic excitation spectra of all possible homo-and heteronuclear high-spin (quartet) trimers of K and Rb (K x Rb 3ÿx , x 0 . . . 3) assembled on the surface of superfluid helium droplets, are measured in the spectral range from 10 600 to 17 400 cm ÿ1 . A regular series of corresponding bands is observed, reflecting the similar electronic structure of all these trimers. For the assignment and separation of overlapping bands, we determine x directly, with mass-selected beam depletion, and indirectly with a V-type double-resonance scheme. The assignment is confirmed by high-level ab initio calculations of the electronic structure of the bare trimers. The level structure is rationalized in terms of harmonic-oscillator states of the three valence electrons in a quantum-dot-like confining potential. We predict that three should be a magic number for high-spin alkali clusters.

Journal of Physics B-atomic Molecular and Optical Physics, 2006

ABSTRACT KRb and Rb2 dimers are formed on cold helium nanodroplets. Laser excitation and emission... more ABSTRACT KRb and Rb2 dimers are formed on cold helium nanodroplets. Laser excitation and emission spectra from the transition (1)3Πg–3Σu+ of Rb2 and the transition (2)3Π–3Σ+ of KRb have been measured. A thorough analysis of the emission, which takes place after desorption of the dimers from the surface of the helium cluster, has been performed. It allows us to determine the redistribution of vibrational population on the droplet surface. A comparison of the experimental spectra with simulations, obtained with the potential energy curves and dipole moments calculated by Aymar and Dulieu, allows a test of the accuracy of the ab initio potentials.