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LABORATORY
ATOMIC SPECTROSCOPY

HEAD: Assoc.Prof. Kiril Blagoev, Ph.D.
tel: 7144-646; e-mail: kblagoev@issp.bas.bg

TOTAL STAFF: 9
RESEARCH SCIENTISTS: 7

D.Zechev
P.Pramatarov
R.Dyulgerova
M.Stefanova
V.Mihailov
E.Dimova
G.Malcheva
V.Penchev, PhD student
N.Parvanova, PhD student


RESEARCH ACTIVITIES:

I. ATOMIC STRUCTURE, SPECTRA AND CONSTANTS

    Radiative lifetimes of excited states of Zn I ( 3d104sns 3S1, n = 6-8; 3d104snd 3D, n = 4-7), Zn II (3d104p 2P1/2,3/2, 4d 2D3/2,5/2, 3d105s 2S1/2) and 11 levels belonging to the 5s5p 1Po1 , 5snd 3D1,2 (n=6-9) and 5sns 3S1 (n=7, 8) series of Cd I, and of 5 levels of Cd II (i.e. 4d105p 2Po1/2,3/2, 4d106s 2S1/2 and 4d105d 2D3/2,5/2) have been measured using a time-resolved laser-induced fluorescence technique. Single - or two-step excitation of atoms and ions produced by laser ablation was employed. Branching fractions of Cd II transitions have been measured by laser-induced breakdown spectroscopy.

    Experimental transition probabilities arising from 4d8 5s2, 4d9 6s and 4d9 5d levels of Ag II and 3d8 4s2 level of Cu II were measured. A time-resolved system with a Nd-YAG laser that produced free neutral and ionised silver and cooper plasma by ablation was used. Transition probabilities were deduced by measured branching ratio and experimental and theoretical data for radiative lifetimes.

    Excitation transfer process between 4,3He(21P, 21S) and N2 is investigated by means of time resolved method after pulse electron excitation. The corresponding rate constants and cross sections are obtained.

II. HOLLOW CATHODE DISCHARGE - PROPERTIES AND APPLICATION

    The performed comparative experiments on both oriented and aligned ensemble of sputtered atoms and buffers are the first to demonstrate and prove their different own coherent conductivity. He-Cd and pulse day-lasers have been used to enlarge this type of measurements under various excited states.

    The photo-emission OG signal (in absent of the discharge) have been investigated to eliminate this galvanic component in the conventional OG signal.

    Photo-luminescent emission of new kind of electroluminescent structures are investigated.

    The improved scanning photoelectric registration apparatus employed for registration of emission spectra as an analytical signal in depth profile analysis in hollow cathode discharge, especially for "in situ" measurement of the sputtering rates of the consecutive layers.

    Depth profile analysis in hollow cathode discharge is carried out of the SnO2/SiO2/Si structure with modified surface by hexamethildisilazane, developed as a basis of solid state gas sensors. The depth profile of the different elements in this structure is obtained as a function of the rapid thermal annealing and concentration of the modified layer. Additionally, this structure is analysed by Auger- and XPS- methods. The results obtained by these different methods help an interpretation of the changes in the structure, which is necessary for optimisation of the technological conditions for its production.

III. HOLLOW CATHODE DISCHARGAS AN ACTIVE LASER MEDIA

    Experimental and theoretical investigation on the negative glow plasma of the hollow cathode discharge in 3Íå-Ne è 4Íå-Ne gas mixtures is carried out. The observed enhanced laser operation on the NeI 1.15 mm line of about 4 times in 3Íå-Ne is explained. The results from the calculations show that the electron temperature is lower and the gas temperature is higher in 3Íå-Ne gas mixture compared to 4Íå-Ne gas mixture. This results in weaker deexcitation of the upper laser level 2s2 by electrons and by collisions with He atoms. The inner multiplet mixing of 2p levels plays important role in the inversion population mechanism. The lower electron temperature leads to lower population of the 2p4 level. The enhanced laser operation is due to the increased rate constant of the process of excitation transfer between Íå (23S1) and Ne ground state atom; and increased saturated Íå(23S1) metastable atom density as a result of decreased step-wise ionization and increased role of the process of three body recombination of He ions.


PUBLICATIONS:
  1. G. Dobrikov, K. Kolentsov, D. Zhechev, L. Yourukova, M. Rassovska, H. Yosifov and N. Parvanova, Photoluminescent effects in conjugated polymer layers Vacuum 2004 (accepted for publication)
  2. D. Zhechev, Nely Parvanova and V. Grigorieva, Ar+→Cd sputtering-atomizing and coherent-galvanic effects in hollow cathode discharge, Vacuum 2004 (accepted for publication)
  3. R.Djulgerova, B.Pantchev, V.Mihailov, V.Gencheva, J.Flaga - "Concentration profiles of ion exchanged optical waveguides in glass analysed in hollow cathode plasma" - Surface & Coatings Technology 166 (2003) 201-201
  4. K. Blagoev, E. Dimova and G. Petrov, "Quenching of 4He(21S, 21P) and 3He(21S, 21P) states by collisions with Ne(1S0) atoms", JQSRT, (2003), (accepted )
  5. E. Dimova, G. M. Petrov and K. B. Blagoev, "Quenching of 4He and 3He excited states by collisions with N2", VACUUM, 2003, (accepted )
  6. K. B. Blagoev, G. Malcheva, V. Penchev E. Biemont H. L. Xu, A. Persson and S. Svanberg "Radiative Lifetimes of Zn I, II Excited States", Physica Scripta 2003(accepted)

TEACHING ACTIVITIES:

Two PhD students - V. Penchev and N. Parvanova
Organization of the Sixth winter seminar of young scientists


ONGOING RESEARCH PROJECTS:
  1. Photo-induced effects in low temperature plasma and solid state surface: photo-resonant and surface photo-charge effects" with BAS
  2. Micro Hollow Cathode Discharge and applications (supported by Nat Sci Fund, 2003-2006)
  3. Radiative lifetimes and transition probabilities of excited atomic and ionic states.
  4. Interaction of He (and He isotope) metastable and resonance states with Ne, N, H atoms.
  5. Measurement and to comparision of the 3He and 4He singlet and triplet metastable densities in the various active laser media. The relative intensities of the spectral lines from the upper and lower laser levels will be investigated as well.

INTERNATIONAL COLLABORATION:
  1. Possibilities of hollow cathode discharge as a plasma sputtering source for production and investigation of new materials - Institute of Physics of Jagellonian University, Poland - Dr. R. Djulgerova
  2. Analysis of multy-component materials - problems and applications - Institute of Physics of Belgrade, Serbia and Montenegro - Dr. R.Djulgerova
  3. EC Program "Improving Human Potential - Access to Research Infrastructures" HPRI-CT-1999-00041. - Dr. K. Blagoev
  4. International collaboration under the Problem "Laser spectroscopy of low-living isomers" with Laboratory of Nuclear Reactions, Dubna, Russia - DSc. D. Zhechev
  5. EU Program COST 529 Efficient Ligthning of 21th century - Dr. K. Blagoev
  6. Atomic spectra and constants, structure and properties University of Madrid, Spain - Dr. K. Blagoev

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