L'excitation simultanée de deux transitions de rotation d'un gaz ayant un niveau d'énergie commun... more L'excitation simultanée de deux transitions de rotation d'un gaz ayant un niveau d'énergie commun fait apparaître des phénomènes liés à cette double irradiation. Nous avons réalisé un spectromètre particulièrement bien adapté à l'étude de ces phénomènes. Ce spectromètre met en 0153uvre un asservissement en phase des oscillateurs de pompe et de sonde et une modulation par tout ou rien de la puissance de pompe suivie d'une démodulation synchrone du signal de sonde. Notre dispositif présente des possibilités d'utilisation, une résolution et une sensibilité qui n'avaient jamais été obtenues dans ce domaine. Abstract. 2014 By use of phase locking of the pumping and signal oscillators added to both an "on-off" switching of the pumping power and a phase detection of the signal, we have built a spectrometer particularly suitable for the study of double resonance phenomena occuring in microwave gaseous spectroscopy. Such an apparatus exhibits utilization and resolving possibilities together with a sensitivity never yet reached in this domain.
2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dan... more 2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dans les expériences de double résonance hertzien-hertzien. L'accord entre les résultats expérimentaux et une théorie basée sur le formalisme de l'hamiltonien habillé est tout à fait satisfaisant. Abstract. 2014 The authors exhibit signal saturation phenomena in microwave double resonance experiments. The agieement between theoretical calculations by means of the dressed hamiltonian formalism and experimental results is fairly good.
The effect of fluctuations on the scaling law in dynamical hysteresis is examined. For moderate v... more The effect of fluctuations on the scaling law in dynamical hysteresis is examined. For moderate values of the sweeping frequency (0) and amplitude A, experiments show that the evolution of the loop area scales as (A0)", the exponent s equal to 2/3 in the absence of fluctuation becomes l/3 in the fluctuation-dominated case.
The effect of the source FM noise on the lineshape in sub-Doppler saturation spectroscopy is exam... more The effect of the source FM noise on the lineshape in sub-Doppler saturation spectroscopy is examined both theoretically and experimentally. We show that the line profile is simply given by the convolution of the homogeneous profile with an "effective" spectrum, depending on the relative values of the sample relaxation time and of the source frequency correlation time but not departing significantly from the source field power spectrum in the usual cases. This result is well supported by a millimeter wave experiment involving a nearly perfect source, frequency modulated by a Gaussian noise.
observing microwave echoes of a polar gas at very low pressure in inhomqeneous Stark fields. effe... more observing microwave echoes of a polar gas at very low pressure in inhomqeneous Stark fields. effects due to molecular motion have been exhl%ited. A naive calculation neglecting molecule collisions is proposed and discussed. Other applications are also briefly presented. * Work suPported in P&t by C.N.R.S. contract A.T.P. no. 2065 and presented in p&al fulfdment for the degree of Docteur 2s Sciences by P. Clorieux..
The effect of the sweeping velocity on the hysteresis loop of a bistable system is examined in th... more The effect of the sweeping velocity on the hysteresis loop of a bistable system is examined in the case where the velocity is so large that the system is prevented from undergoing any transition during the forward sweep. The experiments, made on optical and electronic devices, evidence a dramatic instability ("hesitation") of the return path of the hysteresis loop for a critical value of the sweeping velocity. The main features of this generic phenomenon are well covered by a one-dimensional analytic theory which provides scaling laws in good agreement with the observations.
Abstract Transient phenomena occurring in time resolved microwave-microwave double resonance expe... more Abstract Transient phenomena occurring in time resolved microwave-microwave double resonance experiments when the pump power is switched on and off have been investigated both theoretically and experimentally. Special attention has been paid to the case when both fields are saturating and exactly resonant. A calculation using the evolution operator formalism has been carried out to explain the experimental results. Transient nutations similar to those observed by the Stark modulation method have been observed and theoretically explained. A new phenomenon, the driven induction decay, has also been observed when the pump power is switched on. Moreover, double resonance photon echoes have also been exhibited. The application of these methods to relaxation studies is discussed.
We theoretically revisit the problem of the propagation of coherent light pulses through a linear... more We theoretically revisit the problem of the propagation of coherent light pulses through a linear medium when the carrier frequency of the pulses coincides with the minimum of a narrow dip in the medium transmission. Considering realistic contrasts between the maximum and minimum transmission of the medium and incident pulses of strictly finite duration, we combine temporal and spectral approaches to obtain analytical expressions of the transmitted pulse that reproduce the main features of the exact numerical solutions derived by fast Fourier transform. A special attention is paid to the advance of the pulse maximum over that of a pulse covering the same distance in vacuum and the ratio of this advance to the pulse duration (fractional advance) is optimized.
2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dan... more 2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dans les expériences de double résonance hertzien-hertzien. L'accord entre les résultats expérimentaux et une théorie basée sur le formalisme de l'hamiltonien habillé est tout à fait satisfaisant. Abstract. 2014 The authors exhibit signal saturation phenomena in microwave double resonance experiments. The agieement between theoretical calculations by means of the dressed hamiltonian formalism and experimental results is fairly good.
... r elle sym trique en cloche, la correction donn e par (28) entraine une simple compression de... more ... r elle sym trique en cloche, la correction donn e par (28) entraine une simple compression de l'impulsion dont le maximum continue de ... 311 Volume 49, number 5 OPTICS COMMUNICATIONS 1 April 1984 Je remercie JL Qu va, F. Rohart, B. Segard et A. Van Groenendael pour ...
L'excitation simultanée de deux transitions de rotation d'un gaz ayant un niveau d'énergie commun... more L'excitation simultanée de deux transitions de rotation d'un gaz ayant un niveau d'énergie commun fait apparaître des phénomènes liés à cette double irradiation. Nous avons réalisé un spectromètre particulièrement bien adapté à l'étude de ces phénomènes. Ce spectromètre met en 0153uvre un asservissement en phase des oscillateurs de pompe et de sonde et une modulation par tout ou rien de la puissance de pompe suivie d'une démodulation synchrone du signal de sonde. Notre dispositif présente des possibilités d'utilisation, une résolution et une sensibilité qui n'avaient jamais été obtenues dans ce domaine. Abstract. 2014 By use of phase locking of the pumping and signal oscillators added to both an "on-off" switching of the pumping power and a phase detection of the signal, we have built a spectrometer particularly suitable for the study of double resonance phenomena occuring in microwave gaseous spectroscopy. Such an apparatus exhibits utilization and resolving possibilities together with a sensitivity never yet reached in this domain.
2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dan... more 2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dans les expériences de double résonance hertzien-hertzien. L'accord entre les résultats expérimentaux et une théorie basée sur le formalisme de l'hamiltonien habillé est tout à fait satisfaisant. Abstract. 2014 The authors exhibit signal saturation phenomena in microwave double resonance experiments. The agieement between theoretical calculations by means of the dressed hamiltonian formalism and experimental results is fairly good.
The effect of fluctuations on the scaling law in dynamical hysteresis is examined. For moderate v... more The effect of fluctuations on the scaling law in dynamical hysteresis is examined. For moderate values of the sweeping frequency (0) and amplitude A, experiments show that the evolution of the loop area scales as (A0)", the exponent s equal to 2/3 in the absence of fluctuation becomes l/3 in the fluctuation-dominated case.
The effect of the source FM noise on the lineshape in sub-Doppler saturation spectroscopy is exam... more The effect of the source FM noise on the lineshape in sub-Doppler saturation spectroscopy is examined both theoretically and experimentally. We show that the line profile is simply given by the convolution of the homogeneous profile with an "effective" spectrum, depending on the relative values of the sample relaxation time and of the source frequency correlation time but not departing significantly from the source field power spectrum in the usual cases. This result is well supported by a millimeter wave experiment involving a nearly perfect source, frequency modulated by a Gaussian noise.
observing microwave echoes of a polar gas at very low pressure in inhomqeneous Stark fields. effe... more observing microwave echoes of a polar gas at very low pressure in inhomqeneous Stark fields. effects due to molecular motion have been exhl%ited. A naive calculation neglecting molecule collisions is proposed and discussed. Other applications are also briefly presented. * Work suPported in P&t by C.N.R.S. contract A.T.P. no. 2065 and presented in p&al fulfdment for the degree of Docteur 2s Sciences by P. Clorieux..
The effect of the sweeping velocity on the hysteresis loop of a bistable system is examined in th... more The effect of the sweeping velocity on the hysteresis loop of a bistable system is examined in the case where the velocity is so large that the system is prevented from undergoing any transition during the forward sweep. The experiments, made on optical and electronic devices, evidence a dramatic instability ("hesitation") of the return path of the hysteresis loop for a critical value of the sweeping velocity. The main features of this generic phenomenon are well covered by a one-dimensional analytic theory which provides scaling laws in good agreement with the observations.
Abstract Transient phenomena occurring in time resolved microwave-microwave double resonance expe... more Abstract Transient phenomena occurring in time resolved microwave-microwave double resonance experiments when the pump power is switched on and off have been investigated both theoretically and experimentally. Special attention has been paid to the case when both fields are saturating and exactly resonant. A calculation using the evolution operator formalism has been carried out to explain the experimental results. Transient nutations similar to those observed by the Stark modulation method have been observed and theoretically explained. A new phenomenon, the driven induction decay, has also been observed when the pump power is switched on. Moreover, double resonance photon echoes have also been exhibited. The application of these methods to relaxation studies is discussed.
We theoretically revisit the problem of the propagation of coherent light pulses through a linear... more We theoretically revisit the problem of the propagation of coherent light pulses through a linear medium when the carrier frequency of the pulses coincides with the minimum of a narrow dip in the medium transmission. Considering realistic contrasts between the maximum and minimum transmission of the medium and incident pulses of strictly finite duration, we combine temporal and spectral approaches to obtain analytical expressions of the transmitted pulse that reproduce the main features of the exact numerical solutions derived by fast Fourier transform. A special attention is paid to the advance of the pulse maximum over that of a pulse covering the same distance in vacuum and the ratio of this advance to the pulse duration (fractional advance) is optimized.
2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dan... more 2014 Les auteurs ont mis en évidence des phénomènes de saturation dus à la puissance de sonde dans les expériences de double résonance hertzien-hertzien. L'accord entre les résultats expérimentaux et une théorie basée sur le formalisme de l'hamiltonien habillé est tout à fait satisfaisant. Abstract. 2014 The authors exhibit signal saturation phenomena in microwave double resonance experiments. The agieement between theoretical calculations by means of the dressed hamiltonian formalism and experimental results is fairly good.
... r elle sym trique en cloche, la correction donn e par (28) entraine une simple compression de... more ... r elle sym trique en cloche, la correction donn e par (28) entraine une simple compression de l'impulsion dont le maximum continue de ... 311 Volume 49, number 5 OPTICS COMMUNICATIONS 1 April 1984 Je remercie JL Qu va, F. Rohart, B. Segard et A. Van Groenendael pour ...
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