N. Bouloufa - Academia.edu (original) (raw)

Papers by N. Bouloufa

Congrès Générale Société Française de Physique, 2011

a^{a}a I. Russier, F. Martin, C. Linton, P. Crozet, A.J. Ross, R. Bacis and S. Churassy, J. Mol. ... more $^{a}$ I. Russier, F. Martin, C. Linton, P. Crozet, A.J. Ross, R. Bacis and S. Churassy, J. Mol. Spectroscopy, 168, 39 (1994)

Journal de Physique II, 1992

Journal of the Chinese Chemical Society, 2002

Pushing the Frontiers of Atomic Physics - Proceedings of the XXI International Conference on Atomic Physics, 2009

ABSTRACT The cold-molecules field is very active trying to transfer laser cooling techniques from... more ABSTRACT The cold-molecules field is very active trying to transfer laser cooling techniques from atoms to molecules. Photoassociation of cold atoms, followed by spontaneous emission of the electronically excited molecules, produces translationally cold molecules, but in several vibrational levels v of the ground state. We have recently shown that vibrational cooling can be obtained by optical pumping with a shaped broadband femtosecond laser. The broadband laser electronically excites the molecules, leading via a few absorption - spontaneous emission cycles to a redistribution of the vibrational population in the ground state. By removing the laser frequencies corresponding to the excitation of the v = 0 level, a dark state is produced by the so-shaped laser, yielding with successive laser pulses an accumulation of the molecules in the v = 0 level.

Science, 2008

The methods producing cold molecules from cold atoms tend to leave molecular ensembles with subst... more The methods producing cold molecules from cold atoms tend to leave molecular ensembles with substantial residual internal energy. For instance, cesium molecules initially formed via photoassociation of cold cesium atoms are in several vibrational levels ν of the electronic ground state. We applied a broadband femtosecond laser that redistributes the vibrational population in the ground state via a few electronic excitation/spontaneous emission cycles. The laser pulses are shaped to remove the excitation frequency band of the ν = 0 level, preventing re-excitation from that state. We observed a fast and efficient accumulation (∼70% of the initially detected molecules) in the lowest vibrational level, ν = 0, of the singlet electronic state. The validity of this incoherent depopulation pumping method is very general and opens exciting prospects for laser cooling and manipulation of molecules.

Physical Review A, 2003

Recently, an unusual predissociation was observed for some vibrational levels of the B 1Piu molec... more Recently, an unusual predissociation was observed for some vibrational levels of the B 1Piu molecular state of 6Li7Li [Bouloufa et al., Phys. Rev. A 63, 042507 (2001)]. It was interpreted as due to the ungerade-gerade symmetry breaking that couples the B 1Piu quasibound levels to the 1 1Pig continuum. However, the agreement between theory and experiment was not perfect for

Physical Review A, 2001

In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. ... more In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. [J. Chem. Phys. 111, 1926 (1999)], where the dissociation of vibrational levels due to the tunneling through the potential barrier was investigated, several vibrational levels with abnormally large dissociated rates were observed in the case of the 6Li7Li isotopomer. This dynamical effect cannot be explained by tunneling as in the case of 6Li2 or 7Li2. A simple model of coupling between B1Pi(u) and 1(1)Pi(g) states involving the u-g symmetry breaking for 6Li7Li is proposed. Rates of the B1Pi(u) predissociated levels due to this coupling are calculated. A good agreement with the experiment is found.

Physical Review A, 2009

Using a non-selective broadband detection scheme we discovered an efficient mechanism of formatio... more Using a non-selective broadband detection scheme we discovered an efficient mechanism of formation of ultracold Cs2 molecules in deeply bound levels (v = 1 − 9) of their electronic ground state X 1 Σ + g. They are formed by a one-photon photoassociation of ultracold cesium atoms in a manifold of excited electronic states, followed by a two-step spontaneous emission cascade. We were able to form about 10 5 − 10 6 molecules per second in these low vibrational levels of the ground state. This detection scheme could be generalized to other molecular species for the systematic investigation of cold molecule formation mechanisms.

Physical Review A, 2011

The electrostatic interaction between an excited atom and a diatomic ground state molecule in an ... more The electrostatic interaction between an excited atom and a diatomic ground state molecule in an arbitrary rovibrational level at large mutual separations is investigated with a general second-order perturbation theory, in the perspective of modeling the photoassociation between cold atoms and molecules. We find that the combination of quadrupole-quadrupole and van der Waals interactions compete with the rotational energy of the dimer, limiting the range of validity of the perturbative approach to distances larger than 100 a.u.. Numerical results are given for the long-range interaction between Cs and Cs 2 , showing that the photoassociation is probably efficient whatever the Cs 2 rotational energy.

Physical Review A, 2007

A reexamination of the photoassociation spectrum of the external well of the 0 g − potential of C... more A reexamination of the photoassociation spectrum of the external well of the 0 g − potential of Cs 2 converging to the ͑6s 1/2 +6p 3/2 ͒ limit is performed, in order to resolve inconsistencies arising from a previously published paper ͓Phys. Rev. Lett. 85, 1408 ͑2000͔͒. We use the same analytical description of the potential as in an other previous analysis ͓Phys. Rev. A 66, 052506 ͑2002͔͒, but we make a shift of 2 in the assignment of the observed vibrational lines. The agreement between experimental and calculated energy positions is improved and the intensities calculated using the new potential account well for all available data. The fitting procedure reveals a strong interdependence of the parameters of the model, which limits the accuracy of the determination of the radiative lifetimes of the 6p 2 P 1/2 and 6p 2 P 3/2 atomic levels. Only a more precise experimental study could allow one to improve the determination of these lifetime values.

Physical Chemistry Chemical Physics, 2011

Translationally cold caesium molecules are created by photoassociation below the 6s + 6p(1/2) exc... more Translationally cold caesium molecules are created by photoassociation below the 6s + 6p(1/2) excited state and selectively detected by resonance enhanced two photon ionization (RE2PI). A series of excited vibrational levels belonging to the 0(-)(g) symmetry is identified. The regular progression of the vibrational spacings and of the rotational constants of the 0(-)(g) (6s + 6p(1/2)) levels is strongly altered in two energy domains. These deviations are interpreted in terms of resonant coupling with deeply bound energy levels of two upper 0(-)(g) states dissociating into the 6s + 6p(3/2) and 6s + 5d(3/2) asymptotes. A theoretical model is proposed to explain the coupling and a quantum defect analysis of the perturbed level position is performed. Moreover, the resonant coupling changes dramatically the spontaneous decay products of the photoexcited molecules, strongly enhancing the decay into deeply bound levels of the a(3)Σ(+)(u) triplet state and of the X(1)Σ(+)(g) ground state. These results may be relevant when conceiving population transferring schemes in cold molecule systems.

Physica Scripta, 2009

When the atoms of a dimer remain most of the time very far apart, in so-called longrange molecula... more When the atoms of a dimer remain most of the time very far apart, in so-called longrange molecular states, their mutual interaction is ruled by plain atomic properties. The highresolution spectroscopic study of some molecular excited states populated by photoassociation of cold atoms (photoassociative spectroscopy) gives a good illustration of this property. It provides accurate determinations of atomic radiative lifetimes, which are known to be sensitive tests for atomic calculations. A number of such analyses has been performed up to now, for all stable alkali atoms and for some other atomic species (Ca, Sr, Yb). A systematic review of these determinations is attempted here, with special attention paid to accuracy issues.

Molecular Physics, 2010

Photoionization spectroscopy of cold cesium dimers obtained by photoassociation of cold atoms in ... more Photoionization spectroscopy of cold cesium dimers obtained by photoassociation of cold atoms in a magneto-optical trap is reported here. In particular, we report on the observation and on the spectroscopic analysis of all the excited states that have actually been used for efficient detection of cold molecules stabilized in the triplet a 3 Σ + u ground state. They are: the (1) 3 Σ + g state connected to the 6s+6p asymptote, the (2) 3 Σ + g and (2) 3 Π g states connected to the 6s+5d asymptote and finally the (3) 3 Σ + g state connected to the 6s + 7s asymptote. The detection through these states spans a wide range of laser energies, from 8000 to 16500 cm −1 , obtained with different laser dyes and techniques. Information on the initial distribution of cold molecules among the different vibrational levels of the a 3 Σ + u ground state is also provided. This spectroscopic knowledge is important when conceiving schemes for quantum manipulation, population transfer and optical detection of cold cesium molecules.

Journal of Molecular Spectroscopy, 2000

The sub-Doppler analysis of the (A 1 ⌺ ϩ-X 1 ⌺ ϩ) system is performed for 6 LiH and 7 LiH by cros... more The sub-Doppler analysis of the (A 1 ⌺ ϩ-X 1 ⌺ ϩ) system is performed for 6 LiH and 7 LiH by crossing an effusive beam of LiH by a cw tunable laser beam in the near UV; 384 lines are measured between 357 and 385 nm and assigned to 6 LiH and 7 LiH with an accuracy of 5 ϫ 10 Ϫ3 cm Ϫ1. Accurate Dunham coefficients and their mass-dependent corrections are deduced for the A 1 ⌺ ϩ electronic state of both isotopomers from the combination of previously published data and these new ones.

The Journal of Chemical Physics, 2004

An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative ... more An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C (1)Sigma(+) state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C (1)Sigma(+) state and the continuum of the A (1)Sigma(+) state and to vary with the vibrational quantum number, from nanoseconds to milliseconds. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.

Congrès Générale Société Française de Physique, 2011

a^{a}a I. Russier, F. Martin, C. Linton, P. Crozet, A.J. Ross, R. Bacis and S. Churassy, J. Mol. ... more $^{a}$ I. Russier, F. Martin, C. Linton, P. Crozet, A.J. Ross, R. Bacis and S. Churassy, J. Mol. Spectroscopy, 168, 39 (1994)

Journal de Physique II, 1992

Journal of the Chinese Chemical Society, 2002

Pushing the Frontiers of Atomic Physics - Proceedings of the XXI International Conference on Atomic Physics, 2009

ABSTRACT The cold-molecules field is very active trying to transfer laser cooling techniques from... more ABSTRACT The cold-molecules field is very active trying to transfer laser cooling techniques from atoms to molecules. Photoassociation of cold atoms, followed by spontaneous emission of the electronically excited molecules, produces translationally cold molecules, but in several vibrational levels v of the ground state. We have recently shown that vibrational cooling can be obtained by optical pumping with a shaped broadband femtosecond laser. The broadband laser electronically excites the molecules, leading via a few absorption - spontaneous emission cycles to a redistribution of the vibrational population in the ground state. By removing the laser frequencies corresponding to the excitation of the v = 0 level, a dark state is produced by the so-shaped laser, yielding with successive laser pulses an accumulation of the molecules in the v = 0 level.

Science, 2008

The methods producing cold molecules from cold atoms tend to leave molecular ensembles with subst... more The methods producing cold molecules from cold atoms tend to leave molecular ensembles with substantial residual internal energy. For instance, cesium molecules initially formed via photoassociation of cold cesium atoms are in several vibrational levels ν of the electronic ground state. We applied a broadband femtosecond laser that redistributes the vibrational population in the ground state via a few electronic excitation/spontaneous emission cycles. The laser pulses are shaped to remove the excitation frequency band of the ν = 0 level, preventing re-excitation from that state. We observed a fast and efficient accumulation (∼70% of the initially detected molecules) in the lowest vibrational level, ν = 0, of the singlet electronic state. The validity of this incoherent depopulation pumping method is very general and opens exciting prospects for laser cooling and manipulation of molecules.

Physical Review A, 2003

Recently, an unusual predissociation was observed for some vibrational levels of the B 1Piu molec... more Recently, an unusual predissociation was observed for some vibrational levels of the B 1Piu molecular state of 6Li7Li [Bouloufa et al., Phys. Rev. A 63, 042507 (2001)]. It was interpreted as due to the ungerade-gerade symmetry breaking that couples the B 1Piu quasibound levels to the 1 1Pig continuum. However, the agreement between theory and experiment was not perfect for

Physical Review A, 2001

In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. ... more In the recent sub-Doppler experiment on the B1Pi(u) state of the Li2 molecule by Bouloufa et al. [J. Chem. Phys. 111, 1926 (1999)], where the dissociation of vibrational levels due to the tunneling through the potential barrier was investigated, several vibrational levels with abnormally large dissociated rates were observed in the case of the 6Li7Li isotopomer. This dynamical effect cannot be explained by tunneling as in the case of 6Li2 or 7Li2. A simple model of coupling between B1Pi(u) and 1(1)Pi(g) states involving the u-g symmetry breaking for 6Li7Li is proposed. Rates of the B1Pi(u) predissociated levels due to this coupling are calculated. A good agreement with the experiment is found.

Physical Review A, 2009

Using a non-selective broadband detection scheme we discovered an efficient mechanism of formatio... more Using a non-selective broadband detection scheme we discovered an efficient mechanism of formation of ultracold Cs2 molecules in deeply bound levels (v = 1 − 9) of their electronic ground state X 1 Σ + g. They are formed by a one-photon photoassociation of ultracold cesium atoms in a manifold of excited electronic states, followed by a two-step spontaneous emission cascade. We were able to form about 10 5 − 10 6 molecules per second in these low vibrational levels of the ground state. This detection scheme could be generalized to other molecular species for the systematic investigation of cold molecule formation mechanisms.

Physical Review A, 2011

The electrostatic interaction between an excited atom and a diatomic ground state molecule in an ... more The electrostatic interaction between an excited atom and a diatomic ground state molecule in an arbitrary rovibrational level at large mutual separations is investigated with a general second-order perturbation theory, in the perspective of modeling the photoassociation between cold atoms and molecules. We find that the combination of quadrupole-quadrupole and van der Waals interactions compete with the rotational energy of the dimer, limiting the range of validity of the perturbative approach to distances larger than 100 a.u.. Numerical results are given for the long-range interaction between Cs and Cs 2 , showing that the photoassociation is probably efficient whatever the Cs 2 rotational energy.

Physical Review A, 2007

A reexamination of the photoassociation spectrum of the external well of the 0 g − potential of C... more A reexamination of the photoassociation spectrum of the external well of the 0 g − potential of Cs 2 converging to the ͑6s 1/2 +6p 3/2 ͒ limit is performed, in order to resolve inconsistencies arising from a previously published paper ͓Phys. Rev. Lett. 85, 1408 ͑2000͔͒. We use the same analytical description of the potential as in an other previous analysis ͓Phys. Rev. A 66, 052506 ͑2002͔͒, but we make a shift of 2 in the assignment of the observed vibrational lines. The agreement between experimental and calculated energy positions is improved and the intensities calculated using the new potential account well for all available data. The fitting procedure reveals a strong interdependence of the parameters of the model, which limits the accuracy of the determination of the radiative lifetimes of the 6p 2 P 1/2 and 6p 2 P 3/2 atomic levels. Only a more precise experimental study could allow one to improve the determination of these lifetime values.

Physical Chemistry Chemical Physics, 2011

Translationally cold caesium molecules are created by photoassociation below the 6s + 6p(1/2) exc... more Translationally cold caesium molecules are created by photoassociation below the 6s + 6p(1/2) excited state and selectively detected by resonance enhanced two photon ionization (RE2PI). A series of excited vibrational levels belonging to the 0(-)(g) symmetry is identified. The regular progression of the vibrational spacings and of the rotational constants of the 0(-)(g) (6s + 6p(1/2)) levels is strongly altered in two energy domains. These deviations are interpreted in terms of resonant coupling with deeply bound energy levels of two upper 0(-)(g) states dissociating into the 6s + 6p(3/2) and 6s + 5d(3/2) asymptotes. A theoretical model is proposed to explain the coupling and a quantum defect analysis of the perturbed level position is performed. Moreover, the resonant coupling changes dramatically the spontaneous decay products of the photoexcited molecules, strongly enhancing the decay into deeply bound levels of the a(3)Σ(+)(u) triplet state and of the X(1)Σ(+)(g) ground state. These results may be relevant when conceiving population transferring schemes in cold molecule systems.

Physica Scripta, 2009

When the atoms of a dimer remain most of the time very far apart, in so-called longrange molecula... more When the atoms of a dimer remain most of the time very far apart, in so-called longrange molecular states, their mutual interaction is ruled by plain atomic properties. The highresolution spectroscopic study of some molecular excited states populated by photoassociation of cold atoms (photoassociative spectroscopy) gives a good illustration of this property. It provides accurate determinations of atomic radiative lifetimes, which are known to be sensitive tests for atomic calculations. A number of such analyses has been performed up to now, for all stable alkali atoms and for some other atomic species (Ca, Sr, Yb). A systematic review of these determinations is attempted here, with special attention paid to accuracy issues.

Molecular Physics, 2010

Photoionization spectroscopy of cold cesium dimers obtained by photoassociation of cold atoms in ... more Photoionization spectroscopy of cold cesium dimers obtained by photoassociation of cold atoms in a magneto-optical trap is reported here. In particular, we report on the observation and on the spectroscopic analysis of all the excited states that have actually been used for efficient detection of cold molecules stabilized in the triplet a 3 Σ + u ground state. They are: the (1) 3 Σ + g state connected to the 6s+6p asymptote, the (2) 3 Σ + g and (2) 3 Π g states connected to the 6s+5d asymptote and finally the (3) 3 Σ + g state connected to the 6s + 7s asymptote. The detection through these states spans a wide range of laser energies, from 8000 to 16500 cm −1 , obtained with different laser dyes and techniques. Information on the initial distribution of cold molecules among the different vibrational levels of the a 3 Σ + u ground state is also provided. This spectroscopic knowledge is important when conceiving schemes for quantum manipulation, population transfer and optical detection of cold cesium molecules.

Journal of Molecular Spectroscopy, 2000

The sub-Doppler analysis of the (A 1 ⌺ ϩ-X 1 ⌺ ϩ) system is performed for 6 LiH and 7 LiH by cros... more The sub-Doppler analysis of the (A 1 ⌺ ϩ-X 1 ⌺ ϩ) system is performed for 6 LiH and 7 LiH by crossing an effusive beam of LiH by a cw tunable laser beam in the near UV; 384 lines are measured between 357 and 385 nm and assigned to 6 LiH and 7 LiH with an accuracy of 5 ϫ 10 Ϫ3 cm Ϫ1. Accurate Dunham coefficients and their mass-dependent corrections are deduced for the A 1 ⌺ ϩ electronic state of both isotopomers from the combination of previously published data and these new ones.

The Journal of Chemical Physics, 2004

An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative ... more An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C (1)Sigma(+) state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C (1)Sigma(+) state and the continuum of the A (1)Sigma(+) state and to vary with the vibrational quantum number, from nanoseconds to milliseconds. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.