By investigating Hel spectral lines emitted by helium atoms after 30-50 keV HetHe collisions the post-collisional states of target and projectile atoms can be determined. Using in particular level-crossing and anticrossing spectroscopy we found that both target atoms resulting from direct excitation and projectile atoms resulting from capture excitation have extremely asymmetric charge distributions immediately after a collision. These results can be explained by the idea of Paul-trap promotion.

Diode laser absorption spectroscopy (DLAS) in plasmas, flames and electrothermal atomizers and their combination with separation techniques is presented as a simple highly sensitive and robust method for trace analysis of elements and molecular species. The analytical figures of merit of the technique are demonstrated by the measurement of elements relevant in industrial and environmental samples, as well as molecular species including halogen atoms, hydrogen, carbon and sulfur.

While in magnetically confined fusion plasmas the bulk of the hydrogen atoms are ionized, still useful information about the plasma properties can be obtained by spectroscopic observations. Several spectroscopic techniques will be discussed and results of Dopplershift measurements at high resolution will be presented.

In the spectral range between 480 nm and 630 nm the Stark effect of the transitions n ¹Q-2 ¹S, n ¹Q-2 ¹P and n ³Q-2 ³P (n=3÷10, Q=S, P,...) was studied using electric field up to 1500 kV/cm. For such a high field the Stark splitting becomes greater than the simple structure of the atom. Hence anticrossings of the Stark components of the same magnetic quantum number occur. The experimental results have been compared with the theoretically determined shifts. The results of calculations show good agreement with observation.

Self-assembled nanoscale arrays of controllable geometry and composition (up to 8 tetrapyrroles) have been formed via non-covalent binding interactions of the meso-phenyl bridged Zn-octaethylporphyrin chemical dimers or trimers with di- /tetrapyridyl substituted porphyrin extra-ligands. In these complexes using steady-state and time-resolved (ps fluorescence and fs pump-probe) measurements pathways and efficiencies of the energy transfer photoinduced charge separation as well as exchange d-π effects have been studied in solutions of variable polarity at 77-293 K. The same principles of aggregation via the key-hole scheme "Zn-pyridyl" have been used also for the surface passivation of pyridylsubstituted tetrapyrroles on the coreshell semiconductor CdSe/ZnS quantum dots (QD) showing quantum confinement effects. Picosecond time-resolved and steady-state data reveal that CdSe/ZnS QD emission is multiexponential and the efficiency of its quenching by attached porphyrins (due to energy transfer and photoinduced charge separation) depends strongly on the number of anchoring groups their arrangement in the porphyrin molecule as well as on QD size and number of ZnS monolayers. The analysis of spectroscopic and kinetic findings reveals that on average only ~l/5 porphyrin molecules are assembled on the QD and a limited number of "vacancies" accessible for porphyrin attachment is available on the QD surface.

Magnetic resonance imaging (MM) using optically polarized ³He is a new and very promising diagnostic method for studying structure and function of lungs. A novel low field MRI system based on permanent magnet and a home-built ³He polarizing unit is presented. The system is designed to perform experiments on small animals. First ¹H and ³He images of phantoms small biological objects and rat lungs in vivo are shown.

Autofluorescence-endogenous fluorescence of cells and tissues has been known for many years. For a long time it has been considered mostly a phenomenon producing unwanted background impairing a quality of fluorescence microscopic images. First reports on a diagnostic potential of the autofluorescence for a detection of premalignant and malignant lesions were published only at the end of 1990. This paper presents basic ideas of such techniques and their applications in the field of tumor detection.

Recent investigations of neodymium and praseodymium using high resolution spectroscopy of atoms and ions in a hollow cathode and a Paul trap have produced new results. Some selected aspects of these experimental methods will be discussed.

We investigated elastic light scattering on isolated evaporating droplets of radius between 1 and 20 tim. The droplets were either pure water or a water based suspension they carried electric charge and were contained in an electrodynamic trap. The evolution of the trapped droplet was investigated by means of scatterometry. A numerical model of such evolution incorporating the kinetic effects near the droplet surface was constructed. For water droplets with spherical inclusions the radius as well as effective refractive index was determined. An essential deviation in the form of a resonance from predictions by standard effective medium theories was encountered. Simple analysis of the phenomenon was conducted and a qualitative explanation is proposed. Similar analysis was applied to fullerene water suspension droplets in order to investigate the real part of refraction index.

The lowest Rydberg state El (³E⁺) of the CdNe CdAr and CdKr van der Waals complex has been investigated by an optical-optical double resonans (OODR). Two electronic states: AO⁺(5³P₁) and B1 (5³P₁) have been used as intermediates for probing the final E1(6³S₁) state. We have measured the bound-bound laser excitation spectra of the E1² AO⁺ transition which correspond to the first observation of the bound CdNe/CdAr/CdKr complexes in the El state. By means of Birge-Sponer (BS) linear plot of the v'-progression we estimated the spectroscopical parameters of the potential well of the Cd(6³S₁)-Ne(2¹S₀)/Ar (3¹S₀)/Kr(4¹S₀) interactions. On the other hand in the excitation spectrum of the El ² Bl transition we observed the characteristic nodal structure of a bound-free absorption which can be elucidated by the Franck-Condon (FC) projection of vibrational wave-function of the Bl state onto the "hump" of the E- state potential as it was predicted by ab initio calculations of Czuchaj and Stoll. Assuming Morse function as an adequate approximation of the inner El potential well we simulated the observed bound-bound spectra and hence we obtained some additional information regarding the location of the potential well minimum (R_e). By the use of B1 state as an intermediate we were also able to observe some bound-bound spectra related to a second (shallow) minimum in the potential energy curve and to evaluate its potential parameters. Simple energy considerations makes also possible an evaluation of the height of potential barriers predicted theoretically in the potential energy curves of the E1 state. Generally our results are in a reasonable agreement with the ab initio calculated results.

Adiabatic potential energy curves for twenty six low-lying electronic states of Li₂ dimer have been computed in the large range of internuclear distances (3.2 a₀ ≤ R ≤ 80 a₀). Four singlet states (4¹Σ⁺_u, 2¹Π_u, 2¹Π_g and 1¹Δ_g) and four triplet states (5³Σ⁺_u, 2³Π_u, 2³Π_g and 1³Δ_u) and are presented for the first time. In the calculations the complete-active-space multi-configuration self-consistent-field (CASSCF) method has been used. The core-polarization potential (CPP) has been also added to the hamiltonian. A good agreement with previous theoretical and experimental results has been obtained.

We investigated laser-based spectroscopic techniques: phase-conjugate degenerate four-wave mixing (PC-DFWM) and laser Thomson scattering (LTS) in terms of their application to Stark profile studies in thermal plasma. PC-DFWM was used for the Stark profile determination while LTS served for plasma diagnostic purpose. Experiments were performed for thermal plasma generated in the transferred arc and burning in pure argon at atmospheric pressure. The spectral profile of the 696.543 nm ArI line was studied. Our attention was paid to the problem of the laser power influence on the measured quantities and plasma state. In the case of PC-DFWM the influence of the laser power manifests itself as broadening of the line profile that can be corrected by a simple extrapolation of the results to the zero laser intensity. On the other hand the results of the Thomson scattering show strong dependence of the electron temperature on the laser intensity and its variations during the laser pulse.

Excitation and fluorescence ultraviolet spectra of 12-group homonuclear metal dimers (i.e., M₂, where M=Zn, Cd and Hg) recorded at several molecular transitions provide information on interatomic potentials of the ground and low-lying excited electronic energy states of the dimers. In experiments the molecules were produced in a supersonic beam and were excited in a vacuum chamber using a dye-laser beam. Well-resolved vibrational structures in excitation spectra isotopic and rotational structures of the vibrational components as well as Condon internal diffraction patterns in the fluorescence bands were recorded and analyzed. Analyses of the excitation spectra lead to the analytical representations of the ground- and excited-state interatomic potentials. Analyses of the fluorescence profiles yielded information on the repulsive parts of the ground-state interatomic potentials. In the case of Cd₂ and Hg₂ the results confirm a relatively soft repulsion between two metal atoms in the short-range region of internuclear separation and make allowance for a theoretically predicted covalent admixture to the ground-state van der Waals binding. The hypothesis needs further corroboration. The determined interatomic potentials of mercury dimers were used in a proposed mechanism of vibrational cooling in translationally cold Hg₂.

A problem of kinetic fluorescence and emission anisotropy decays of the intramolecular charge transfer (ICT and TICT) compounds in polar and non-polar (but highly polarizable) solvents will be discussed. It will be shown that the application of appropriate kinetic approximations (high- and low-temperature approximations) enables a direct determination of the kinetic rates describing the two-excited-state processes. Experimental examples for DMABN (4-(dimethyl amino) benzonitrile) and related compounds will be compared. A problem of TICT (Twisted Intramolecular Charge Transfer) mechanism will be discussed. The discussion will be supported by considering the emission anisotropy decays of DMABN in the solvents of different viscosity and which provide further evidence for TICT mechanism in DMABN and related compounds.

Hyperfine structure of several lines in neutral and singly ionized lead have been measured. The discharge tube containing metallic isotope ²⁰⁷Pb was used as a light source. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with CCD camera used as a detector. In the analysis of the spectra we used a computer simulation technique. Our experiment yields the following hyperfine splitting constants A: A(6p^{2 1}D₂)=(20.69 ±0.21) mK, A(6p^{2 3}P₂)=(91.37±0.34) mK A(6p7s ¹P₁)=(16.45±0.95) mK, A(6p7s ³P₁)=(293.93±0.56) mK, A(6p6d ³F₂)=(103.22±0.31) mK, A(6p6d ³F₃)=(69.12±0.28) mK, A(6p8s ³P₁)=(202.04±0.48) mK, A(6p8p ³P₁)=(224.26±1.37) mK, A(6p8p ³D₂)=(108.02±1.14) mK, A(6p7d ³D₁)=(-100.86±0.53) mK for the levels of PbI and A(6s² 7s ²S_1/2)=(352.1±1.7) mK, A(6s² 7p ²P_3/2)=(13.6±1.3) mK, A(6s² 7p ²P_1/2)=(70.8±1.1) mK for the levels of Pb II. Our results are compared with recent theory and other experiments.

The purpose of the present work is to discuss the possibility of experimental determination of the collisional reorientation alignment and coherence effects involving magnetic sublevels in case of the j₂=3/2 ← j_l=½ transitions. The use of atomic crossed-beams allow one to control the initial velocity direction in scattering experiments. Moreover the use of polarized laser lights in pump and probe experimental set-up gives the additional information about orbital reorientation and alignment effects in the atomic collisional processes. We analyze the dependence of laboratory cross-section on the angular arrangement of the polarization directions of pump and probe laser beams. The quantum close-coupling calculations for Ca⁺ + He system is used to examine the possibility of experimental determination of the reorientation and alignment effects.

The excited electronic states with internal charge transfer of some molecules show an anomalously strong inhomogeneous broadening of their electronic spectra. The paper presents the results obtained by studying spectral inhomogeneity of the electronic bands of an archetype molecule with intramolecular charge transfer in the excited state dimethylaminobenzonithrile (DMABN) in polar solvents. The inhomogeneity manifests itself in both luminescence and luminescence excitation spectra. The broadening is anomalously large and amounts to 140-150 nm. The interpretation of the obtained results is based on treating a solution as a set of chemically identical solvates with luminophor molecule in the centre which have different energies of the pure electronic transitions. The inhomogeneity arises due to both the intermolecular effect of luminophor environment on its spectra in polar solvents and the existence of various conformers of DMABN. Some of these conformers possess absorption and emission spectra well shifted to the red edge of the spectra and could be selectively excited in the far Antistokes region. The results of kinetic and polarization study of DMABN luminescence at such excitation by picosecond semiconductor laser radiation at 403 nm are presented.

Lidar investigation of the upper seawater layer allows obtaining in real-time and without disturbing the aquatic medium the continuous fluorescence spectra of seawater in visible range of light. These spectra provide the information on concentration of Chloropyll a (Chl a) and colored dissolved organic matter (CDOM) as well as allow distinguishing coastal and open-sea waters. Additionally a comparison between the results of Chi a concentrations obtained by classical laboratory method (on the water samples taken from the surface) and lidar in situ method allows detecting and confirming different (surface) water masses.

The absorption and fluorescence spectra of 2-methylaminofluorenone (I) 2-dimethylaminofluorenone (II) and 2-dimethylamino-9-phenyl(4'-dimethylamino)-9-fluorenol (III) were determined in variety of solvents with different polarities. The Marcus theory has been applied to obtain the outer-sphere reorganization energy, λ_outer, and the innersphere reorganization energies: λ_i^* and λ_i associated with the vibrations for which hv<kT and hv>kT respectively.

The electron cooling and ion heating processes in a positive column of an Ar DC discharge are discussed here. The Particle-In-Cell Monte Carlo (PlC MC) method is used which describes the kinetics of electron and ions in plasma-wall interface. The Langmuir probe is applied to study a flame front propagation under the laminar and turbulent mode of combustion.

The dependence of the optical properties of large sodium clusters as a function of their size is studied. Clusters are light induced allowing observation of the smooth change of their sizes as a result of the spontaneous nucleation process. We combine the formalism of the classical Mie scattering theory for spheres of arbitrary large size and the concept of the collective electron oscillations (plasmons). The maxima in normalized intensities of light scattered by single cluster we attribute to resonant excitation of dipole and quadrupole plasmon oscillation respectively. We show that plasmon resonances take place for different cluster sizes when excited with different wavelength. We compare these results with expectations resulting from solving the problem of eigenfrequencies of free-electron sphere with the dielectric function described within the Lorentz-Drude model.

We re-examine the usual expectations for multipolar plasmon modes of a simple-metal sphere within a classical picture. We show that according to rigorous solution of the eigenvalue problem the complex eigenfrequencies of plasmon modes can be attributed to the sphere of size larger than the minimum size at given multipolarity the feature not known from widely used "low radius limit".

Laser light scattering by a drying droplet of water fullerene suspension several micrometers in size was studied. Two light wavelengths were used. The evolution of refractive index and radius of the droplet was investigated. Resonant scattering was identified and analyzed. Some conclusions were drawn on the microscopic properties of the suspension. Supplementing measurements of samples obtained by drying the water fullerene suspension and toluene solution were conducted with Atomic Force Microscope (AFM).

Evaporation of a droplet of pure water several micrometers in size was investigated. The droplet was levitated in an electrodynamic trap placed in a small climatic chamber. The evolution of the droplet and the evolution dynamics was studied by analyzing the coherent light scattering patterns with the aid of Mie theory. A numerical model of droplet evolution incorporating the kinetic effects near the droplet surface was constructed. By applying this model to the experimental data the mass and thermal accommodation coefficients were determined to be α_C=0.12±0.02 and α_T= 0.65±0.09. This model enabled to find the droplet temperature evolution and the relative humidity in the droplet vicinity with high precision as well.

Two electronic states have been investigated on the basis the First Negative (B²Σ⁺→X²Σ ⁺) system observations in the emission spectrum of the ¹²C¹⁶O⁺ and ¹³C¹⁶O⁺ molecules. For this purpose the conventional technique of hight resolution spectroscopy has been implemented. Thirty eight bands belonging to this system were recorded in the both isotopic species. The reduction of the spectrum for the individual bands has been performed via a nonlinear least-squares fit with the effective Hamiltonian of Brown. As a results of multistage and merged analysis of the currently obtained data and those obtained earlier for the other systems the state of information about energy structure CO⁺ molecule has been significantly enlarged.

Experimental Stark-broadening studies of two NI multiplets (¹D)3s ²D-(¹D)3p ²D° and (¹D)3s ²D-(¹D)3p ²F° are reported. Measurements were performed using a wall-stabilized arc operated at atmospheric pressure in helium with small amounts of nitrogen and hydrogen. The Stark broadening parameters: the electron impact width (w_e)and shift (d_e) have been determined.

Preliminary results of an analysis of profiles of hfs components of the intercombination line of the even-odd ¹¹³Cd isotope perturbed by argon performed by means of a laser-induced fluorescence method are reported and compared with earlier results obtained for even-even ¹¹⁴Cd isotope. It is shown that in the case of ¹¹³Cd isotope the asymmetries ofprofiles are due both to line mixing and collision duration effects.

Polarisational properties of light scattered in turbid media are considered in this paper. First approximation of these media is the model of suspension which includes the group of scattering centres with these same optical properties given by a complex refractive index and various sizes characterised by a size distribution. If any turbid medium is lightened by partly polarised beam of light described by the Stokes vector then the light scattered on the centres might be polarised too. Stokes vectors of incident beam together with scattered beam are connected by sixteen elemental scattering matrix. On the assumption that turbid medium fulfils limitations of the Mie theory (spherical and homogeneous particles and lack of absorption of exterior medium) scattering matrix is reduced to four independent elements. The group of algorithms based on the Mie solution which allow to model those four elements of the scattering matrix was created in the MATLAB. The results of this modelling for an oil emulsion in synthetic seawater are presented.

The polarisation labelling spectroscopy technique was used to observe experimentally the double minimum 4¹Σ⁺_u state in Na₂. Altogether 332 rovibrational levels were identified. Using the modified inverted perturbation approach method (IPA) the physically sensible potential energy curve ofthe state was constructed.

The isotope shift (IS) in two visible lines of neutral lead involving transitions 6s² 6p7s ¹P₁-6s² 6p^{2 1}S₀ (λ5OO.6 nm) and 6s² 6p8s ³P₁-6s² 6p^{2 1}S₀ (λ520.3nm) have been measured using a Fabry-Perot interferometer. The isotope shifts between even isotopic pairs were found to be: v₂₀₈-v₂₀₆=73.3±0.9 mK and v₂₀₈-v₂₀₄=121.4±1.1 mK for 6p7s configuration and v₂₀₈-v₂₀₆=70.1±0.6 mK and v₂₀₈-v₂₀₄=135.7±0.8 mK for 6p8s configuration. The displacements of the centers of gravity of isotope 207 with respect to isotope 208 were determined to be v₂₀₈-v_{207 CG}=46.4±1.2 mK and v₂₀₈-v_{207 CG}=44.9±1.1 mK for 6p7s and 6p8s configurations, respectively.

DMABN, 4-(dimethylaminbenzylonitrile), is the archetype molecule with two broad bands in the luminescence spectra [1,2]. Until now the majority of researchers have connected dual luminescence with different mechanisms of electronic density change (charge transfer) in the excited state. However, the exact nature of its mechanism is still under discussion. Such a model would be the crucial point for the right calculation of photoreactions with CT participation and, therefore, the determination ofthe charge transfer mechanism is the problem ofgreat practical importance. For the proper choice of the model and its groundation a more detailed study is required for establishing additional features ofthe process creating charge transfer in the excited state. We present the results ofquantum-mechanical calculations for DMABN and focus on: 1 . calculations of fundamental characteristics in the states with different geometry and energy; 2. possibilities to create spectral broadening and a study ofthe features ofsuch broadening; The computer programs the HyperChem v.5.0 and the MOPAC 2000 are used in the calculations. A geometry optimization of the ground state is carried out using the PM5 method. Free molecule energy and the values of dipole moments in the excited and the ground states are calculated with the ZINDO/S Cl method assuming that the benzene ring has a fixed flat structure. We have studied geometries with two spatial angles (Fig. ): (p- the torsion (or twist) angle between the planes of the dimethyl group and the benzene ring (0- the angle between the NCC plane and the N-benzene3 bond (wagging angle), the change of which leads to a pyramidal structure

Decay characteristics and polarization of DMABN luminescence at far longwavelength Antistokes excitation by picosecond semiconductor laser radiation at 403 nm are reported. Characteristics of DMABN emission have been registered in different regions of spectra.

The quantum close-coupling studies of the ³P₂<-¹P₁ spin changing transitions in Ba (6s6p) colliding with Ne involving changes of magnetic quantum numbers are presented. The differential and multi-structure cross-section are calculated in a range of relative translational energies from threshold to 0.4 eV. The results of calculations exhibit the Stuckelberg oscillations and strong backward scattering effects.

In the performed experiment we trap simultaneously in the Magneto-Optical Trap cold atoms of ⁷Li with cold sodium atoms and cold ⁶Li atoms with cold ²³Na atoms. We investigated in detail heteronuclear interactions between cold isotopes of lithium atoms and cold sodium atoms in presence of the laser light.

We present our first experimental results of reduced Stokes parameters and electron impact coherence parameters (EICP) for incident electron energy of 60 eV. The electron-photon coincidence technique has been used in measurements for scattering angles 10° and 15°. The experimental data are compared with theoretical results of relativistic distorted wave approximation calculations.

Nonlinear resonances in a quadrupole trap using laser induced fluorescence (LIF) were studied in Nd and Pr for the first time. Two type ofresonances have been recorded : pure coupling resonances and resonances along the trap axis. The relevant parameters of these resonances have been determined.

In laser induced fluorescence signal of Pr⁺ ions stored in a Paul trap an effect of intensity modulation with scanning of the operating point along a axis has been observed. So far only initial results are available and unequivocal interpretation of this effect cannot be given yet but it is most likely concerned with some collective behavior of the ion cloud.

In the present work an effect of space charge in a Paul trap has been observed for selected rare earth elements as a shift of secular frequency of ion motion. For Pr⁺ ions influence of relative number of stored ions on the value of the shift has been examined and initial estimates of the number of ions are given.

Collisions of metastable Mg*(³P) and Ca*(³P, ¹D) atoms with CF₄, CCl₄, and CBr₄ were studied in a beam-gas arrangement. The total attenuation cross sections determined for the reactive systems vary in a wide range increasing with electron affinity of the target gas. The reactions of metastable Mg*(³P) with CX₄ yield no chemiluminescence. All Ca* + CX₄ reactions give electronically excited CaX* products and the chemiluminescence yield increases with reaction exo-ergicity.

Collisions of the metastable Mg*(³P) and Ca*(³P, ¹D) atoms with HF, HCl, HBr, and HI molecules have been studied in a beam-gas arrangement. The total collision cross section were determined from the attenuation of spectral lines emitted by the metastables and when possible from the dependence of chemiluminescence intensity on target gas pressure. The total cross sections for Mg*, Ca* + HC1, HBr, and HI are rather large and indicate harpooning mechanism. The Mg* reactions with HX give no electronic chemiluminescence while the Ca* +HX reactions produce electronically excited CaX* radicals for all HX targets studied. For the latter reactions electronic chemiluminescence cross sections and photon yields were determined.

Absorption spectra of the ZnKr and ZnXe collision molecules are measured in the ±1200cm^-1 frequency range around the Zn 213.8 nm line. Quantum simulations ofthese spectra for the existing theoretical potentials are performed yielding some corrections of the excited ¹0⁺ state potential energy curve. Van der Waals coefficients for both the excited states (¹O⁺ and ¹1) are derived from the near red wing profile analysis.

The blue satellite ofthe Cd resonance line at 228. 8 nm has been studied in both absorption and emission. Comparison of experimental data with quantum simulations of the spectrum basing on available theoretical potential energy curves yielded a correction for the theoretical height of the potential energy barrier in the state 1_u(5¹P₁) Cd. Similar correction seems to be necessary for the analogical state of Zn.

The three adiabatic potential surfaces of the vinoxy radical are calculated. They describe the ground and two lowest excited states. We employ the MCSCF (CASSCF) method using the MOLPRO package.

We report total cross sections (TCS) measurements for positron scattering on N₂, Ar, He and three cyclic hydrocarbons. The data have been obtained with a new linear low-energy spectrometer at Trento University. Both nitrogen and argon total cross sections shows a flat part in TCS from few eV up to the positronium formation thresholds. For cyclocarbons he has found very high values of the TCS in low energy range. Modeling using effective range theory is performed for benzene and cyclohexane. In He results we found some resonant structures indicating formation of virtual positronium.

The Hartree-Fock method in 6-311G** molecular orbitals basis set has been applied to calculations of proton affinities and proton transfer reaction energies for water methanol acetaldehyde ethanol acetone acetic acid methyl acetate and ethyl acetate.

Collisional transfer of excitation energy from cadmium to caesium was investigated using methods of sensitized fluorescence. A mixture of cadmium and caesium vapors at low pressure was irradiated with Cd 3263.0 Å resonance radiation producing a population of Cd (5³P₁) atoms whose inelastic collisions with ground-state Cs atoms resulted in a transfer of excitation energy to a close-lying S, P, D and F states in caesium. The subsequent decay of these states manifested itself in the emission of sensitized fluorescence spectrum. Intensity measurements on the components of the spectrum by means of energy calibrated detector yielded some 50 cross-section values whose magnitudes range from 0.2 Ų to 30.0 Ų and which exhibit a pronounced resonances with ΔE the energy defect between Cd (5³P₁) and the appropriate level in caesium.