N.K. Bibinov

The “approach-induced” and collision-induced transitions from low, vE=8–23, vibronic levels of the I2(E) state

Abstract The dependences of the I 2 ( E0 g + ,v E ,J E → I 2 ( X ) D0 u + ,v D ,J D ) transition rate constants on the vibrational v E , v D , rotational J E , J D quantum numbers, energy gaps, and Franck–Condon factors of the combined levels have been studied in the range v E =8–23. The extremely long-range near-resonance I 2 ( E ,v E → I 2 ( X ) D ,v D ) process as well as nonresonant transitions, corresponding to the energy loss up to ΔE=240 cm −1 (approximately three quanta of vibrational energy), have been observed. Total cross-section of the latter is up to 12 times less than the maximum one of the extremely long-range transition. It has been shown that cross-sections of the processes are independent of initial J E number. The u↔g and ΔΩ=0 propensity rules are valid in the I 2 ( E ) → I 2 ( X ) I 2 (ion-pair states) transitions. The vibrational and rotational populations of the D state levels depend on v E and ΔE . Mechanism of the processes under study has been discussed. It has been shown that essentially nonresonant transitions occur after a mutual I 2 (E) and I 2 (X) capture in orbiting-controlled collision complex. Maybe, one has to take into account relativistic (magnetic) interactions for description of the extremely long-range transitions.

Absolute calibration of the efficiency of a VUV-monochromator/detector system in the range 110 - 450 nm

For determining the efficiency of a vacuum-UV monochromator with a multiplier type PMT-142 in the range 110 - 450 nm two different methods for absolute and six methods for relative calibrations were used. The results of all relative calibrations except for one agree to within an accuracy close to the experimental error in the range of their mutual overlap. The accuracies of the relative efficiency curves were found to be 18, 14, 7, 3, 6 and 10% for the ranges 110 - 120, 120 - 140, 140 - 250, 250 - 350, 350 - 400, and 400 - 450 nm, respectively. Absolute calibrations were performed at 147 and nm with an accuracy of 8% in both cases. The differences in the grating illuminations at the monochromator applications and in the calibration were taken into account. The influences of the accuracies of all operations necessary for the absolute calibration on the overall calibration error were thoroughly analysed. If there are significant differences between the geometries of the system illumination during calibration and during application, they may be the main source of error.

A comparative study of the electron distribution function in the positive columns in and /He dc glow discharges by optical spectroscopy and probes

We compare to the probe method a spectroscopic method for determining in plasmas the electron distribution function (EDF) over a wide energy range. For a test of the radiative-collisional model we use to describe the plasma radiation, the measured vibrational distributions of (C-B) and (B-X) were compared with calculated ones using our model and EDFs measured by Langmuir probes. From this comparison we obtain a value for the rate constant for vibrational relaxation at the walls. In a second step we invert the system of model equations for obtaining the EDF from measured line intensities. From the vibrational structure of the emission spectra of the nitrogen molecule the EDF is obtained in the energy range of 1.5-4.5 eV. From the relative intensities of the emission of nitrogen molecules and helium atoms the EDF for electron energies above 11 eV is derived. In the region between these ranges the EDF is interpolated. The results agree within the limits of the experimental errors with the EDF measured directly by the probe.

The collision-induced transition

Abstract The dependences of the Cl 2 ( D0 u + ,v D ,J D → Cl 2 ( X ) g + E0 g + ,v E ,J E ) collisional induced transition rate constants on the vibrational v E , v D , rotational J E quantum numbers, energy gaps, and Franck–Condon factors of the combined levels have been studied in the range of v D =1–5. It has been shown that all the observed collisional induced intramolecular transitions (CIIT) are nonresonant and correspond to loss of up to 1100 cm −1 vibrational energy. The u↔g and ΔΩ=0 propensity rules are valid in the Cl 2 ( D → Cl 2 ( X ) g + ion-pair states ) CIIT. The vibrational and rotational distributions of the E state levels depend on v D number. For v D =3–5 the E state vibrational level corresponding to maximum Franck–Condon factor with the initial one is mainly populated. The E, v E =0,1,2; β 1 g , v β =2; and E, v E =0 levels are populated from the D, v D =2 and 1 ones, respectively. The “ ΔJ low” propensity rule is valid in the Cl 2 ( D0 u + ,v D =1–5,J D → Cl 2 ( X ) g + E0 g + ,v E =1–5,J E and β1 g ,v β =2,J β ) CIIT. Rotational distribution of the v E =0 levels populated from the v D =1, 2 can be described as the Boltzmann one, T=300 K . The nonadiabatic transitions between potential energy surface corresponding to input Cl 2 (D)+Cl 2 (X) and output Cl 2 (E)+Cl 2 (X) channels occur in relatively short-lived collision complex, and CIIT rate constant is in the (0.4–3.2)×10 −11 cm 3 / s range.

SPECTROSCOPIC DETERMINATION OF COLD ELECTRONS IN ELECTRON CYCLOTRON RESONANCE DISCHARGES WITH HIGHLY CHARGED IONS

A spectroscopic method based on the analysis of molecular and atomic spectra of nitrogen was used for the determination of electron distribution functions (EDFs) in electron cyclotron resonance (ECR) discharges run in nitrogen. EDFs were determined for the plasma region seen by the VUV-monochromator. This region includes the hot core plasma surrounded by a less dense and not so hot halo plasma. The EDF between 1.5 and 4.5 eV was determined from the vibrational distribution of excited molecular states of nitrogen, and that in the energy range above 8.5 eV was evaluated from the intensities of different emission lines and bands of NI and N2. The shape of the EDF in the energy range between 4.5 and 8.5 eV was interpolated by using the electron density measured with Langmuir probes and normalizing the EDF to the same density. Due to the low gas pressure of 2×10−5 Torr vibrational relaxation processes on the discharge chamber wall had to be taken into account. In the wavelengths range 30–400 nm the emission sp...

Electric dipole moment function of the beta 1(3P2)toA 1 3Pi transition in ICl

The optical-optical double-resonance technique has been used for measurements of emission spectra from separate vibrational levels of the 1(3P2) state of ICl (v´ = 12 and 14) populated via the A 1 3 state. The electric dipole moment function of the A transition has been determined over the range of the internuclear distance of 0.29-0.39 nm by means of simulation of the emission spectra from the state.