Control of collision and radiation dynamics in atomic and molecular systems

In Latvian

 

Research group

                            Macis Auzinsh, Prof. Dr. Habil. Phys

                            Janis Kļavins, leading researcher, Dr. Phys

                            Aigars Ekers, researcher, Dr. Phys

                            Janis Alnis researcher, Dr. Phys

                            V. Gruševskis researcher, Mag. Phys

                            Konstantin Orlovsky, researcher, Mag. Phys

                            Kaspars Miculis, PhD student

                            Kaspars Bluss, PhD student

 

Central to our work are problems in interaction of coherent radiation with atoms and molecules and atomic and molecular collision dynamics.

Specifically we study how with laser radiation absorption coefficient of gas can be manipulated. In particular we study appearance of dark and bright resonances when alkali atoms are interacting with coherent radiation from a diode laser in the presence of the external magnetic field. Experiments are carried out on Rb(85), Rb (87) and Cs(133) atoms in broad range of excitation intensity. A theoretical model for these processes based on the density matrix formalism in the approximation of broad spectral line excitation is under development.

Fig. Experimentally recorded and simulated fluorescence Hanle-effect
and level – crossing signals in Rb showing good agreement.

 

1.      J. Alnis, M. Auzinsh, J. Phys. B. 34, 3889 (2001)

2.      Alnis, J. and M. Auzinsh, J. Phys. B: At., Mol. and Opt. Phy., 34: 3889 (2001)

 

 

Another direction of studies is connected with atoms in extremely thin (~ 100 nm) optical cells. We study Cs(133) atoms in presence of an external magnetic field. Changes in a spectrum of laser-induced fluorescence as dependant on the magnetic field strength are observed. We study these changes experimentally as well as model these spectra. Theoretical model is based on the analysis of changes of density matrix of atoms as a result of hyperfine state wave function mixture in the magnetic field. This mixture also changes the positions of spectral lines and the transitions probabilities between different hyperfine atomic levels.


Fig. Experiment with Cs in extremely thin cell.

D. Sarkisyan, D. Bloch, A. Papoyan, M. Ducloy, Opt. Communic. 200, 201 (2001)

 

 

The next problem we will work on is a study of the possibilities of the creation of cold molecules in large density by means of adiabatic transport of molecular gas in a bended octupole magnetic field. We will study model object – Rb atoms and practical test will perform on S2 molecules. The influence of nonadiabatic transitions that can reduce a yield of cold atoms and molecules will be studied theoretically as well as experimentally. The ultimate goal of these studies is to use these cold molecules to increase accuracy of permanent electric dipole moment measurements for an electron in order to test the standard model.

Fig. Adiabatic transport guide for obtaining of cold atoms and molecules.

 

B. Ghaffari, J.M. Gerton, W.I. McAlexander, K.E. Strecker, D.M. Homan,
R.G. Hulet, Phys. Rev. A. 60, 1349 (1999)

 

We will continue to study excited n2F states of K atoms obtained in the process of two-laser excitation. In 2003 we plan to measure energy transfer between highly excited atomic state in transitions with large changes of angular momentum quantum number Dl = 3. These data can allow further development of a theory of ground state atom – highly excited state atomic collision processes.

 

   Głódź M., Huzandrov A., Klavins J., et.al., Acta Phys. Pol. A 98 (2000) 353.

 

In year 2003. we will further develop methods used in our research group aimed in measuring pollutant gases in the technological and environmental processes. In particular we are planning to further develop method to measure concentration of NO2 gas in combustion processes. Method is based on modulation spectroscopy with IR diode laser.

 

1. J. Alnis et. al. Appl. Phys. Lett. 76, 1234 (2000).

2. U. Gustavfsson, J. Alnis et. al., Am. J. Phys. 68, 660 (2000).

 

 

Finally we will continue to study the chemical reaction dynamics of sodium atoms in a Rydberg states with vibrationaly excited Na2(v) molecule. In this process sodium positive and negative ions are created. Our aim is to determine contribution of several possible mechanisms in the ion formation. The possible schemes of ion formation are dissociative attachment of a quasi-free Rydberg electron to the molecule with further dissociation, or formation of a triatomic reaction complex with further decay into products.

 

  1. O. Kaufmann, A. Ekers, et al., Int. J. Mass. Spectrom.205, 233 ( 2001).
  2. A.Ekers, O. Kaufmann, K. Bergmann, Latv. J. Phys. Tech. Sci. 1, 51 (2002).