Electronic-excitation transfer collisions in flames-VII. Some alkali-doublet mixing cross sections for inert gas collisions,at 1720 K

Doublet mixing cross sections for K(4²P)-Ar and He and for Rb(5²P)-He collisions have been measured, in flames at 1720 K. The ratio σ₁₂/σ₂₁ was measured separately and was found to agree within 2 per cent with predictions derived from detailed balance. The experiments are compared with available semiclassical theoretical results.     

Electronic-excitation transfer collisions in flames-III: Cross sections for quenching and doublet mixing of Rb(52P32, 12) doublet by N2, O2, H2 and H2O

Weighted average quenching cross sections for the Rb(5²P) doublet by N₂ and H₂O were determined in flames with temperatures ranging from 1500 to 2500 K by measuring the fluorescence efficiency. The values found are $\text{(σ}{}_{\mathrm{qu}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= (19±2)}\text{A}\text{?}{}^2$ and over the entire temperature range. At a temperature of 1720 K, mixing cross sections were obtained for the same doublet with N₂, H₂, O₂ and H₂O molecules. The cross sections found are: $\text{σ}{}_{21}\text{(}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{→}{}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= (60±12)}\text{A}\text{?}{}^2$, $\text{σ}{}_{12}\text{(}{}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{→}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= 99±20)}\text{A}\text{?}{}^2$; , $\text{(σ}{}_{21}\text{)}{}_{\mathrm{<mtext>H</mtext><mtext>2</mtext>}}\text{> 30}\text{A}\text{?}{}_2$, $\text{(σ}{}_{12}\text{)}{}_{\mathrm{<mtext>H</mtext><mtext>2</mtext>}}\text{> 50}\text{A}\text{?}{}^2\text{;}$, . The ratios σ₁₂/σ₂₁ were measured independently and were found to agree with the detailed- balance condition within 3 per cent. A critical comparison of the flame values with previous literature data on N₂-cross sections shows that both mixing and quenching cross sections are temperature dependent in the range from 300 to 2500 K.     

Temperature dependence of the quenching of the Na-D-doublet by nitrogen molecules

By inclusion of an attractive part of the interaction potential into the ionic curve-crossing model theory for the quenching of the Na-D-doublet by nitrogen molecules, the discrepancy between theory and experiments may be removed.     

Electronic-excitation transfer collisions in flames—VI. Interpretation of the temperature dependence of alkali-quenching by N2 and general conclusions about the energy transfer mechanism

The experimental temperature dependence of alkali-N₂ quenching cross sections is explained semi-quantitatively by a simple theoretical model, based on an ionic intermediate state, in which attractive van-der-Waals forces play an essential role. Using this model, quenching experiments are compared with Na(3²P)-N₂ excitation measurements in molecular beams. From this comparison it is concluded that the distribution of relative cross sections for specific vibrational transitions during the quenching process can be described by a distribution calculated by Fisher,⁽⁸⁾ whereas the distribution given by Bjerre⁽¹⁸⁾ has to be rejected. Resonant vibrational-electronic energy transfer is not important.     

Quenching of excited strontium atomic state measured in H2- and CO-flames

The efficiency of resonance fluorescence, Y, of the strontium resonance line (¹P₁→¹S₀ transition) at 4607.33 Å was measured in CO/N₂O, CO/O₂/Ar, and H₂/O₂/CO₂/N₂ flames at atmospheric pressure. From these data, the specific quenching cross sections, σ_qu, for CO₂ and CO were found to be (60 ± 10) Ų and  (300 ± 60) Ų, respectively. The experimental cross sections were confronted with the intermediate ionic-state curve-crossing model and chemical quenching model, respectively.     

Electronic-excitation transfer collisions in flames—V. Cross sections for quenching and doublet-mixing of K(42P)-doublet by N2, O2, H2 and H2O

Weighted average cross sections for quenching of the K(4²P)-doublet by N₂, H₂, O₂ and H₂O, measured in flames, show no significant temperature dependence in the range from 1500 to 2500K. Doublet mixing cross sections for K(4²P$\text{3}\text{2}$?4²P$\text{1}\text{2}$) transitions were measured at 1720K for N₂, O₂, H₂O. The ratios of both mixing cross sections were measured independently and were found to agree with the detailed balance condition within 2 per cent. It is shown that an ionic intermediate-state model cannot explain the large magnitude of N_2? mixing cross sections.     

Electronic-excitation transfer collisions in flames—II temperature dependence of the quenching of Na(32P)-doublet by H2 and O2

Effective cross sections for quenching of the Na(3²P)-doublet by H₂ and O₂ molecules have been measured in flames in the temperature range 1500–2500 K. The H₂-cross section decreases from (9.3±1.0) Ų at 1500 K to (6.8±1.0) Ų at 2500 K. The O₂-cross section decreases from (39±2) Ų at 1720 K to (31±2) Ų at 2500 K. A critical comparison of the flame values with previous literature data on the H₂-cross section at lower temperatures shows that it decreases systematically when the temperature rises from about 400 to 2500 K.