In the present study we have shown that the dissociative recombination of Ne2+ ions which gives rise to non-thermalized Ne atoms may be regarded as the main process responsible for the distortion of the profiles of the 753.5 and 754.4 nm neon lines. The distorted profiles were analysed as a superposition of the Ballik profile for thermalized atoms and the modified Ballik profile for non-thermalized atoms and the Lorentzian and Gaussian widths as well as the relative density of non-thermalized and thermalized atoms have been determined. We have found for the dissociation energy of the neon molecular ion Ne2+ in the 2 Sigma u+ state the value D=(1.20+or-0.08) eV. We have also found for the 3d6 excited neon atoms of speed 1275 m s-1 the excitation transfer cross section Q3d6 with a value Q3d6=(39+or-15)*10-16 cm2.

The broadening and shift of four spectral lines arising from the 2p53p-2p56s transitions of neon emitted from a low pressure glow discharge in pure neon and a neonhelium mixture have been measured. The values of the pressure broadening and shift coefficients are determined. The results are interpreted in terms of the impact theory assuming the Lennard-Jones potential. Results obtained in this work indicate that the Lennard-Jones potential cannot describe adequately the broadening and shift of the spectral lines under investigation.

The effect of molecular oxygen on the broadening and shift of the 535.0 nm TI line resulting from the photodissociation of thallium iodide vapour was studied at low densities of O2. The broadening and shift coefficients were determined.As a sequel to previous papers [1 -3] this note reports results of measurements of the Doppler-and pressure-broadened profiles of the green thallium fluorescence line 535.0 nm (7s 2 SI/2 -6p ^3/2) accompanying the photodissociation of Til molecules in thallium iodide vapour mixed with oxygen used as perturbing gas.The experimental and numerical procedures used to study the half-widths of the Lorentzian and Gaussian components of the 535.0 nm TI line have been described in detail in references [1 -3]. An r.f. electrodeless mercury discharge lamp was used to excite the photodissociation of the Til vapour in a fluorescence cell kept at temperature of 733 K. The measurements were performed for thallium iodide-oxygen mixtures at the constant Til density and at different densities of 02 up to 2 x 10 18 cm -3 which corresponds to pressures of 02 below 50 Torr at room temperature. Intensity distributions in the broadened line were measured using a grating spectrograph and a pressure scanned Fabry-Perot etalon with 1.204 cm spacer and dielectric coating of mirrors. A low pressure r.f. electrodeless thallium discharge lamp operating at 100 MHz was applied as the reference source in the line shift determination.Similarly as in our previous work [1 -3] we have found that the resultant shape of the 535.0 nm TI line emitted due to the photodissociation of Til can be fitted well enough to a Voigt profile which * This work was carried on under the Research Project M.R.I.5.Reprint requests to Dr. E. Lisicki, Institute of Physics, Nicholas Copernicus University, Grudziadzka 5, 87-100 Torun, Poland.is the convolution of the Lorentzian and Gaussian profiles. To determine the magnitudes of the halfwidths 7D and yL of the Gaussian and Lorentzian components of the total line shape, respectively, a procedure given by Ballik [4] combined with a least squares method was used. Figure 1 shows the plots of the Gaussian and Lorentzian half-widths as well as the shift A of the maximum of the 535.0 nm TI line against the oxygen density. We should emphasize that the Gaussian half-width yD of the 535.0 nm TI line emitted from the TlI-02 mixture is practically constant over the whole density range. Its average value y^> is equal to 0.055 cm -1 . This value is close to the values /D = 0.055 cm" 1 for T1I + H, [1], /D = 0.0512 cm" 1 for T1I + D2 [2] and yD = 6.051 cm" 1 forTlI + N2 [3]. The Gaussian half-width corresponding to the usual Doppler broadening due to the thermal motion of TI atoms with the Maxwellian velocity distribution at 733 K is equal to 0.020 cm -1 . Thus the additional Doppler broadening arising from the recoil of the excited TI 7 2 Si/2 atom after the photodissociation of Til [5] can be estimated from the difference 7B -7 A to be 0.035 cm -1 .As can be seen from Fig 1 both the Lorentzian half-wid...

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