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Mesure des profils de redistribution collisionnelle donnant un accord avec la suggestion selon laquelle le profil de l'aile rouge lointaine dans le cas de MgH 2 est domine par une absorption conduisant aux canaux de sortie reactive non radiative. Des profils theoriques bases sur les donnees de courbes de potentiel sont en bon accord avec l'experience

This laser induced fluorescence study of NaAr reports the direct observation of vibrational and rotational structure of the B2∑+ state through spectroscopic means of Reference 1. Crossed laser and supersonic molecular beam technique is used. We study highly excited vibrational levels at both A2∏r and B2∑+ states. Several types of rotation induced perturbations are encountered and analyzed. Preliminary intensity calculations for the B‐X system lead us to believe that the adiabatic B2∑+ well minimum must be at smaller internuclear distance than has been estimated before. We estimate that 5.5 A < RBe < 6 A and that the B2∑+ state is at least 30 cm−1 deep. This is in agreement with the latest high resolution scattering data2.

We have observed K2 Rydberg electronic states of 1Δg and 1Σ+g symmetry using CW optical‐optical double resonance techniques in the energy range 28920–30050 cm−1 above the ground state minimum. Resolved fluorescence from the 1Σ+g states to the A1Σ+u state allows us to observe the lowest (v

The long range potential of the Na2 A1∑+u state has been investigated by studying various properties of the excited vibrational levels that it supports. Many high lying rovibrational levels in the range J’=10, 12, v’=43‐105 have been observed using the technique of Modulated Gain Spectroscopy. This has allowed us to characterize the intramolecular to a maxium intranuclear separation of 10.7 A) using an RKR inversion procedure.

A linearly polarized tunable CW dye laser was used to photodissociate K2 from the ground X1Σ+g state through the continuum of the B1Πu state. By monitoring the resultant atomic D2 fluorescence, we were able to measure the pure bound‐free absorption profile. At the same time, the polarization of the atomic fluorescence was measured as a function of laser excitation frequency. We believe this to be the first observation of a large variation in the polarization, ranging from plus 15±2% to minus 6.3±0.4% as a function of laser wavelength. The results can be explained in terms of molecular rotation during dissociation. These results are consistent with a completely adiabatic model for the dissociation. However, there are significant discrepancies between these model results and the experimental observations when hyperfine depolarization effects are included in the calculation. The origin of these discrepancies is not understood.

Twenty additional 23Πg vibrational levels and 5 additional 13Δg vibrational levels of Na2 below the previously reported levels have been observed by perturbation Facilitated Optical‐Optical Double Resonance (PFOODR) spectroscopy. Absolute vibrational numberings and molecular constants of these two states are determined.

We report on our studies of the far wing absorption of laser light into the MgH2 reactive collision complex. We have measured the absorption profile leading to both the non‐reactive channel (Mg* formation) and into a specific ro‐vibrational state of the reactive channel (MgH (v‘=0, J‘=23) and have developed a simple theoretical model to explain some of the general features of the results.

The far wing absorption of laser light to the collision complex MgH2 leads to nonreactive formation of excited state magnesium, Mg*, and reactive formation of MgH [1]. Far wing absorption of laser light is monitored by observation of the final product (Mg* or MgH) as a function of pump laser detuning from the magnesium resonance line. We monitor production of MgH (v″ = 0) rotational levels J″ = 6 and J″ = 23, close to low J and high J maxima of a bimodal rotational distribution, respectively. For this we use laser-induced fluorescence in a two laser pump and probe experiment. We also monitor the competing nonreactive channel Mg* by observation of resonance fluorescence Mg (31P 1 0 - 31S0). The onset of the reactive channel in the Mg + H2 system is highlighted through a comparison with far wing profiles from the nonreactive collision system Mg + H2 and the reactive system Mg + H2 [1]. We have developed a simple excited state dynamics model for the theoretical interpretation of our data. This model uses standard quasistatic theory to estimate the absorption probability as a function of detuning of the laser frequency from resonance. The potential energy curve data [2] is limited to fixed geometries, C2v and C∞v. Based on this, only rough comparisons are possible between the dynamics model and experiment.

The spectrum of Fe I has been studied at 0.08 A FWHM resolution using the high-frequency-deflection technique. The lifetimes for all J components of the z 5 F° and y 5 F° levels were simultaneously directly measured.

We have used the experimental energy levels of the B state of Na2 to determine the shape of the potential curve. The potential curve obtained has been used to determine the Franck—Condon overlap of the continuum vibrational levels in the B state with bound levels in the ground electronic state.

We have observed stimulated emission on the transitions 43S1−33PJ° near 518 nm following pulsed laser excitation of Mg vapor near the 31S0−33P1° resonance at 285 nm. The emission has a divergence similar to the pump laser and closely follows the incident laser in time. The mechanism apparently involves pumping an accidental coincidence 31S0−33P1° and 33PJ°−53DJ, permitting depletion of the lower level of the triplet transition. Photoionization of the Mg vapor creates a large electron density (≲1013 cm−3); electron-impact collisions are presumed to mediate the process, transferring population from the laser-pumped 31P1° level to the triplet manifold.