A K-N2(or He)mixture is irradiated in a fluorescence cell with pulses of 770nm radiation from OPO-YAG laser and populated K(4P1/2)state.Cross sections for K(4P1/2)→K(4P3/2)and quenching of the K(4P3/2)state is determined using the atomic fluorescence spectrometry.With the variable densities of N2(or He),the intensities of time-integrated fluorescence from 4P1/2→4S1/2(the direct fluorescence)and 4P3/2→4S1/2(the transfer fluorescence)is measured.The ratio of the fluorescence intensity versus the densities of N2(or He)can be fitted by a straight line,the cross sections are(2.77±0.69)×10-15cm2and(1.62±0.41)×10-15cm2 for K(4P1/2)→ K(4P3/2)by the slop,and the cross sections are(0.40±0.12)×10-15cm2and(0.60±0.18)×10-16cm2 for the K(4PJ)quenching from the intercept.
A K-N2(or He)mixture is irradiated in a fluorescence cell with pulses of 770nm radiation from OPO-YAG laser and populated K(4P1/2)state.Cross sections for K(4P1/2)→K(4P3/2)and quenching of the K(4P3/2)state is determined using the atomic fluorescence spectrometry.With the variable densities of N2(or He),the intensities of time-integrated fluorescence from 4P1/2→4S1/2(the direct fluorescence)and 4P3/2→4S1/2(the transfer fluorescence)is measured.The ratio of the fluorescence intensity versus the densities of N2(or He)can be fitted by a straight line,the cross sections are(2.77±0.69)×10-15cm2and(1.62±0.41)×10-15cm2 for K(4P1/2)→ K(4P3/2)by the slop,and the cross sections are(0.40±0.12)×10-15cm2and(0.60±0.18)×10-16cm2 for the K(4PJ)quenching from the intercept.
Cs vapor was created in a resistively heated,cross-shaped stainless-steel heat-pipe oven with quartz windows.H2 gas filled in the cell for use both as a buffer gas and as a reaction partner.Cs atoms were excited to 6D3/2 state by two-photon absorption.The 7P1/2 and 7P3/2 were populated by the radiative and collisional 6DJ→7PJ′ transition.The cross sections for 6DJ7PJ′ transfer induced by collision with H2 molecules have been determined using methods of atomic fluorescence.The resulting fluorescence included a direct component emitted in the decay of the optically excited state and sensitive component arising from collisionally populated states.The time-integrated fluorescence intensities for atomic transitions 6D5/2→6P3/2,6D3/2→6P3/2,7P3/2→6S1/2 and 7P1/2→6S1/2 were measured at the defferent H2 densities.The relative time-integrated population densities were obtained as a function of H2 densities.By the set of the rate equations,the cross-sections have been determined to be σ6D3/27P3/2=(3.1±0.8)×10-16cm2,σ6D3/27P1/2=(1.7±0.4)×10-16cm2,σ6D5/27P3/2=(1.5±0.4)×10-16cm2 and σ6D5/27P1/2=(1.3±0.3)×10-16 cm2.The cross sections for quenching of 7PJ′ by H2 are(2.5±0.6)×10-16 cm2(for 7P3/2) and(4.0±1.0)×10-16 cm2(for 7P1/2).Evidence suggests that the substantial fraction of quenching cross section is reactive.The relative reactivity with H2 is an order 7P1/27P3/2.
At a Cs density higher than 9 x 10(14) cm(-3), cesium vapor was irradiated in a glass fluorescence cell with pulses of radiation from an YAG-laser-pumped OPO laser, populating 6D(5/2) state by two-photon absorption. Energy transfer in Cs6(D(5/2)) + Cs (6S) collisions was studied using methods of atomic fluorescence. At the different Cs densities, we have measured the time-integrated intensities of the components and fitted a three-state rate equation model to obtain the cross sections. The experimental points were fitted to a straight line very well. The authors converted the gradient and intercept into cross sections. The cross section for 6D(5/2)-->6D(3/2) transfer is (2.1 +/- 0.4) x 10(14) cm2. The cross section for excitation transfer out of the 6D doublet is sigmaQ = (1.6 +/- 0.4) x 10(-14) cm2. The cross section on contains information on reverse energy pooling collisions [i.e., Cs(6D(3/2)) + Cs (6S(1/2))-->Cs(6P) + 6Cs(P)] and contribution from mining in 6Dj-->7P(J'), This latter contribution could be subtracted out using the results of a second experiment. At a Cs density lower than 6.0 x 10(12) cm3, the laser was used to pump the 6D(3/2) and 6D(5/2) states, respectively. The resulting fluorescence included the direct component emitted in the decay of the 6D(J) state and the sensitized component arising from the collisionally populated 7P(J') state. Relative intensities of the components yielded the cross sections. The cross-sections for the processes Cs(6D(5/2)) + Cs(6S(1/2))-->Cs(7P(J')) + Cs(6S(1/2)) are (1.6 +/- 0.5) x 10(-15) cm2. for J'= 3/2 and (6.5 +/- 2.1) x 10(-16) cm2, for J' = 1/2, respectively. The cross-sections for the processes Cs(6D(3/2) + Cs(6S(1/2))-->Cs (7P(J')) + Cs(6S(1/2)) are (1.9 +/- 0.6) x 10(-15) cm2. for J' = 3/2 and (7.6 + 2.4) x 10(-16) cm2, for J' = 1/2, respectively. The 6D(J) -->7P(J'), energy transfer rate coefficient is small. The total quenching rate coefficient out of the 6D(J) state is much larger. Evidence suggests that the quenching of the 6D(J) state is caused predominantly by reverse energy-pooling process. The cross section for this process, i.e., Cs(6D(3/2))+Cs(6S(1/2))-->Cs(6P) + Cs(6P) is (1.3 +/- 0.4) x 10(-14) cm2.
Cs vapor in a glass cell was irradiated with pulses of radiation from a YAG-laser-pumped OPO laser,populating 7DJ state by two-photon absorption.Energy transfer in 7DJ+6S1/2 collision is studied using methods of atomic fluorescence.The resulting fluorescence included a direct component arising from the decay of the optically excited and a sensitized component arising from the collisionally populated state.At the different densities,we have measured the time-integrated intensities of the components and fitted a three-state rate equation model to obtain the cross section σ=(2.9±0.7)×10-14cm2 for 7D5/2→7D3/2 transfer.The cross section for excitation transfer out of the 7DJ doublet are(7.4±2.1)×10-14 cm2(for J=5/2) and(6.6±1.8)×10-14 cm2(for J=3/2),respectively.A comparison with previous results yields that the cross sections for 7DJ→8P transfer are(0.6±0.3)×10-14 cm2(for J=5/2)and(0.8±0.4)×10-14 cm2(for J=3/2),respectively.The 7DJ state is quenched mainly in the reverse energy polling processes(i.e.,7DJ+6S→5D+ 6P).
Potassium vapour, contained together with a buffer gas in a glass fluorescence cell at a controlled temperature, was irradiated with pulsed dye-laser radiation which excited the K atoms to the 5 2 P 1/2 or 5 2 P 3 / 2 state. The effective decay rate of the 5 2 P atoms was determined in relation to the buffer gas densities by methods of fluorescence spectroscopy with time resolution. The experiments yielded the total quenching (depopulation) cross sections of 19, 94 and 120 AA 2 for collisions with H 2 , N 2 and CH 4 molecules, respectively.
The electronic excitation transfer processes, $\mathrm{K}(^{2}P_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}(^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{K}(^{2}S_{\frac{1}{2}})+\mathrm{Rb}(^{2}P_{\frac{1}{2}})+\ensuremath{\Delta}E$ and $\mathrm{K}(^{2}P_{\frac{3}{2}})+\mathrm{Rb}(^{2}S_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{K}(^{2}S_{\frac{1}{2}})+\mathrm{Rb}(^{2}P_{\frac{1}{2}})+\ensuremath{\Delta}E$ have been studied by irradiating a cell containing a nonequilibrium mixture of potassium and rubidium vapors with either the 7665 \AA{} D2 line or the 7699 \AA{} D1 line of the potassium resonance doublet. The resulting collisionally induced rubidium 7948 \AA{} fluorescence signal, isolated by interference filters used in tandem, is detected with a liquid-nitrogen-cooled $S\ensuremath{-}1$ photo-multiplier placed at right angles to the direction of excitation. Measurements of the intensity ratio of the potassium and rubidium fluoresence combined with an optical absorption determination of the rubidium atom density yields the following excitation transfer cross sections: $Q[\mathrm{K}(^{2}P_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}(^{2}P_{\frac{1}{2}})]=2.2 {\AA{}}^{2}\ifmmode\pm\else\textpm\fi{}25%$ and $Q[\mathrm{K}(^{2}P_{\frac{3}{2}})\ensuremath{\rightarrow}\mathrm{Rb}(^{2}P_{\frac{1}{2}})]=2.6 {\AA{}}^{2}\ifmmode\pm\else\textpm\fi{}20%$ at $T=365\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}\ifmmode\pm\else\textpm\fi{}2%$. Throughout an experimental run the potassium and rubidium vapor pressures are varied, but data are taken for only the lowest vapor pressures for which corrections due to resonance radiation imprisonment are unnecessary.
6 2P1/2 ↔ 6 2P3/2 mixing and 6 2S1/2 ← 6 2P1/2,3/2 quenching in cesium, induced in collisions with ground state N2, H2, HD, and D2 molecules, have been investigated using techniques of sensitized fluorescence. Mixtures of cesium vapor and the gases, in which the cesium vapor pressure was kept very low to avoid multiple scattering, were irradiated with each component of the cesium resonance doublet in turn. The fluorescence which contained both components of the doublet was observed in a direction perpendicular to that of the exciting beam. Measurements of the relative intensities of the fluorescent components yielded the following cross sections for mixing and quenching. For Cs–N2 collisions: Q12(2P1/2 → 2P3/2) = 4.7 Å2, Q21(2P1/2 ← 2P3/2) = 25 Å2, Q10(2S1/2 ← 2P1/2) = 77 Å2, Q20(2S1/2 ← 2P3/2) = 69 Å2. For Cs–H2 collisions: Q12 = 6.7 Å2, Q21 = 44 Å2, Q10 = 7 Å2, Q20 = 5 Å2. For Cs–HD collisions: Q12 = 4.8 Å2, Q21 = 32 Å2, Q10 = 4 Å2, Q20 = 3 Å2. For Cs–D2 collisions: Q12 = 4.2 Å2, Q21 = 28 Å2, Q10 = 8 Å2, Q20 = 7 Å2. The Cs–N2 and Cs–H2 cross sections supersede the values published previously (McGillis and Krause 1967). The cross sections Q21 appear to exhibit resonances with molecular rotational transitions.