Excitation transfer between the $6 ^{2}P_{\frac{1}{2}}$ and $6 ^{2}P_{\frac{3}{2}}$ resonance states in cesium, induced by Cs-${\mathrm{N}}_{2}$ and Cs-${\mathrm{H}}_{2}$ collisions, was observed in the first experiment of its kind, in which techniques of sensitized fluorescence are used to investigate collisional mixing between resonance states of alkali atoms in mixtures with molecular gases. The cesium-vapor-gas system, in which the cesium vapor pressure was low enough to avoid radiation trapping, was irradiated with a single component of the resonance doublet. The fluorescent light, which contained both components of the doublet, was monitored at right angles to the direction of excitation. Measurements of relative intensities of the fluorescent components yielded the following cross sections for excitation transfer and for quenching of resonance radiation. For Cs-${\mathrm{N}}_{2}$ collisions: ${Q}_{12}(^{2}P_{\frac{1}{2}}\ensuremath{\rightarrow}^{2}P_{\frac{3}{2}})=3.6$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{21}(^{2}P_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=16.2$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{10}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{1}{2}})=55.2$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{20}(^{2}S_{\frac{1}{2}}\ensuremath{\leftarrow}^{2}P_{\frac{3}{2}})=63.5$ ${\mathrm{\AA{}}}^{2}$. For Cs-${\mathrm{H}}_{2}$ collisions: ${Q}_{12}=6.7$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{21}=29.6$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{10}=11.7$ ${\mathrm{\AA{}}}^{2}$, ${Q}_{20}=6.7$ ${\mathrm{\AA{}}}^{2}$. The large sizes of the excitation-transfer cross sections, which are comparable to the corresponding Cs-Cs cross sections, are attributed to resonances with transitions in the molecules.
Excitation transfer between the 62P21 and 62P23 resonance states in cesium, induced by Cs-N2 and Cs-H2 collisions, was observed in the first experiment of its kind, in which techniques of sensitized fluorescence are used to investigate collisional mixing between resonance states of alkali atoms in mixtures with molecular gases. The cesium-vapor-gas system, in which the cesium vapor pressure was low enough to avoid radiation trapping, was irradiated with a single component of the resonance doublet. The fluorescent light, which contained both components of the doublet, was monitored at right angles to the direction of excitation. Measurements of relative intensities of the fluorescent components yielded the following cross sections for excitation transfer and for quenching of resonance radiation. For Cs-N2 collisions: Q12(2P21\ensuremath→2P23)=3.6A˚2, Q21(2P21\ensuremath←2P23)=16.2A˚2, Q10(2S21\ensuremath←2P21)=55.2A˚2, Q20(2S21\ensuremath←2P23)=63.5A˚2. For Cs-H2 collisions: Q12=6.7A˚2, Q21=29.6A˚2, Q10=11.7A˚2, Q20=6.7A˚2. The large sizes of the excitation-transfer cross sections, which are comparable to the corresponding Cs-Cs cross sections, are attributed to resonances with transitions in the molecules.
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.
4 2P1/2–4 2P3/2 mixing in potassium, induced by collisions with N2, H2, D2, and HD, was studied using techniques of sensitized fluorescence. The potassium vapor-gas systems, in which the potassium vapor pressure was kept very low to avoid radiation trapping, was irradiated with one component of the resonance doublet. The fluorescence which contained both components of the doublet was monitored at right angles to the direction of excitation. The following cross sections for mixing and quenching were obtained from measurements of relative intensities of the fluorescent components. For K–N2 collisions: Q12(2P1/2 → 2P3/2) = 100 Å2, Q21(2P1/2 ← 2P3/2) = 66 Å2, Q10(2S1/2 ← 2P1/2) = 35 Å2, Q20(2S1/2 ←2P3/2) = 39 Å2. For K–H2 collisions: Q12 = 76 Å2, Q21 = 53 Å2, Q10 = 7 Å2, Q20 = 4 Å2. For K–D2: Q12 = 72 Å2, Q21 = 50 Å2, Q10 = 2 Å2, Q20 = 1 Å2. For K–HD: Q12 = 74 Å2, Q21 = 49 Å2, Q20 = 11 Å2, Q20 = 14 Å2. An analysis of these results suggests the presence of resonances with the molecular rotational levels.
3 2P1/2 ↔ 3 2P3/2 excitation transfer in sodium, induced in inelastic collisions with ground-state N2, H2, HD, and D2 molecules, has been investigated in a series of sensitized fluorescence experiments. Mixtures of sodium vapor at a pressure of 5 × 10−7 Torr, and the gases, were irradiated with each NaD component in turn, and the fluorescence which contained both D components was monitored at right angles to the direction of the exciting beam. Measurements of the relative intensities of the NaD fluorescent components yielded the following collision cross sections for excitation transfer. For Na–N2 collisions: Q12(2P1/2 → P3/2) = 144 Å2, Q21(2P1,2 ← 2P3/2) = 76 Å2 for Na–H2 collisions: Q12 = 80 Å2, Q21 = 42 Å2. For Na–HD collisions: Q12 = 84 Å2, Q21 = 44 Å2. For Na–D2 collisions: Q12 = 98 Å2, Q21 = 52 Å2. The cross sections Q21 exhibit a slight resonance effect between the atomic and molecular rotational transitions.
52P1/2 ↔ 52P3/2 mixing and 52S1/2 ← 52P1/2, 2P3/2 quenching in rubidium, induced in collisions with ground state H2, HD, D2, N2, CH4, CD4, C2H4, and C2H6 molecules, have been investigated using methods of sensitized fluorescence. The rubidium vapor mixed with each of the gases was excited in turn by each component of the rubidium resonance doublet, and the resulting fluorescence, emitted at right angles to the direction of the exciting light, was resolved into the two fine-structure components whose intensity ratios were measured in relation to the gas pressure using photon counting techniques. The measurements yielded the following cross sections for the mixing and quenching collisions.For H2: Q12(2P1/2 → 2P3/2) = 11 Å2, Q21(2P1/2 ← 2P3/2) = 15 Å2, Q10(2S1/2 ← 2P1/2) = 6 Å2, Q20(2S1/2 ← 2P3/2) = 3 Å2.[Formula: see text]The mixing cross sections agree with theoretical values within an order of magnitude.
The total cross sections for excitation transfer between the 6 2P1/2 and 6 2P3/2 levels in cesium, induced by collisions of the second kind between cesium and inert gas atoms, have been determined using methods of sensitized fluorescence. The experiments were carried out at a cesium vapor pressure of 1 × 10−6 mm Hg, at which there is no trapping of resonance radiation, and over a range of inert gas pressures extending from 1 to 300 mm Hg. The cross sections Q1(2P1/2 → P3/2) and Q2(2P1/2 ← 2P3/2) are as follows: Cs–He: 5.7 × 10−21 and 3.9 × 10−20 cm2; Cs–Ne: 1.9 × 10−21 and 3.1 × 10−20 cm2; Cs–A: 1.6 × 10−21 and 5.2 × 10−20 cm2; Cs–Kr: 8.3 × 10−21 and 18.4 × 10−20 cm2; Cs–Xe: 7.2 × 10−21 and 27.4 × 10−20 cm2. A mechanism for the excitation transfer is suggested, which involves an interaction between the inert gas atoms and the 6 2P electron in cesium, behaving as a free particle.
2 2 2 2 P ^2 ------P3/2 mixin8 and Pj -----* Si / 2 quenchin8 in potassium and cesium vapors, induced by c o llis io n s with N2> H2, HD and D2, were studied using techniques of se n sitiz e d fluorescence.The m ixtures of a lk a li vapors w ith the various gases, in which the a lk a li vapor pressure was kept low to avoid ra d ia tio n trapping, were irr a d ia te d w ith one component of the appropriate resonance doublet.The fluorescence which contained both components of the doublet, was monitored a t rig h t angles to the d ire c tio n of e x c ita tio n .The measurements of the re la tiv e in te n s itie s of the fluorescent components yielded the to ta l in e la s tic 2 2 2 2 2 cross sections for P mixing, Q12( Pl /2 > P3/2 ^' Q21^ *1/2* P3/2 ^' and quenching, Q10^ P1/2 * S1/2^' Q20^ P3/2 * Sl/2^* In the case of potassium the quenching cross sections for N^, H2> HD and D2 were: Q10 = 35, 7, 11, 2 (£)2 and Q2Q = 39, 4, 14, 1 (£ )2, re sp e c tiv e ly .For the cesium resonance s ta te s the corresponding quenching cross sections O o were: Q10 = 62> 7' 4> 8 ^ and ^20 = 10° ' 5> 3> 7 ^ ' r e s Pe c tiv e ly • The potassium -N2, H2, HD and D2 mixing cross sections were found to be: Q12 = " '7> 75' 6' 74,° ' 72*2 and Q21 = 66*°' 53,2> 50,4, 48,7 re sp e c tiv e ly , only s lig h tly larg e r than the corresponding potassium -inert gas cross se ctio n s.The cesium -N2, H2, HD and D2 mixing cross sections were: Q = 4.7, 6.7, 4.8, 4.2 (£)2 and Q21 = 25.2, 43.8, 32.1, 27.8 (£ )2, resp e c tiv e ly , five orders of magnitude larg er than the cesium -inert gas mixing cross sectio n s. iii R ep ro d u ced with p erm ission o f th e copyright ow ner.Further reproduction prohibited w ithout perm ission.The quenching r e s u lts are c o n sisten t w ith the interm ediate complex th eo ries of quenching in which energy matching between the 2 atomic and m olecular s ta te s is of no importance.The P mixing cross sections do, however, exhibit a marked dependence on the ro ta tio n a l s tru c tu re of the c o llid in g m olecules.The r e s u lts are discussed in terms of induced ro ta tio n a l tra n s itio n s on the basis of which the cross sections ^21^ ^or m^x:'-n8 cesi-uni induced by ortho and para hydrogen are c a lcu lated .