The processes of excitation transfer from the 82S1/2 state to the 62D state of rubidium in Rb(82S1/2) – Rb(52S1/2) and Rb(82S1/2) – H2 collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H2, by two light beams for selective stepwise excitation, the Rb 82S1/2 → 52P3/2 direct fluorescence and the Rb 62D3/2 → 52P1/2 sensitized fluorescence have been measured as a function of H2 gas pressure. The measurements yielded the cross-sections σ(82S1/2 → 62D) and σ*(82S1/2 → 62D) of Rb 82S1/2 → 62D excitation transfer induced by collisions with 52S1/2 Rb atom and H2 molecules respectively. The results are discussed in detail.
The cross sections for fine-structure transition (FST) of Rb(7 2 D ) atoms induced by collision with molecules of H 2 and CO have been experimentally determined by the method of selective stepwise excitation of Rb atoms and observation of the resulting fluorescence. The cross sections (in units of 10 -14 cm 2 ) for Rb(7 2 D )-H 2 are σ fs *(7 2 D 5/2 → 7 2 D 3/2 ) = 0.16 ± 0.03, σ fs *'(7 2 D 3/2 → 7 2 D 5/2 ) = 0.24 ± 0.05, for Rb(7 2 D )-CO: σ fs * = 0.10 ± 0.06 and σ fs * ' = 0.15 ± 0.09. The cross sections σ tr * for transfer out of the 7 2 D doublet were also determined.
Cross sections for $7^{2}D_{\frac{3}{2}}\ensuremath{\leftrightarrow}7^{2}D_{\frac{5}{2}}$ transfer in Rb, induced in collisions with He, Ne, Ar, and with ground-state Rb atoms, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a noble gas, was irradiated in a glass fluorescence cell with pulses of 660-nm radiation from a
N2-laser-pumped dye laser, populating one of the
2D states by two-photon absorption. The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated state. Relative intensities of the components yielded the cross sections for
72D mixing: $Q(^{2}D_{\frac{3}{2}}\ensuremath{\rightarrow}^{2}D_{\frac{5}{2}})=8.8,6.5,10.4, \mathrm{and} 30$; $Q(^{2}D_{\frac{3}{2}}\ensuremath{\leftarrow}^{2}D_{\frac{5}{2}})=5.8,4.0,6.9, \mathrm{and} 18$, in units of ${10}^{\ensuremath{-}14}$
cm2 for He, Ne, Ar, and Rb, respectively. Cross sections for the effective quenching of the
2D states were also determined.
Cross sections for inelastic transfer between the 82D3/2 and 82D5/2 fine-structure states in rubidium, induced in resonant collisions with ground-state Rb atoms, have been determined using an experimental method involving two-photon excitation of atomic fluorescence. Rubidium vapor in a fluorescence cell was irradiated with pulses of 641 nm radiation from a N2 laser-pumped dye-laser tuned to excite one of the 82D states. The resulting fluorescence included the direct component originating from the optically excited state and a sensitized component arising from the other fine-structure state populated by collisions. Relative intensities of the fluorescent components, determined by photon-counting techniques, yielded the cross sections for excitation transfer: Q(2D3/2 → 2D5/2) = 8.1 × 10−13 cm2; Q(2D3/2 ← 2D5/2) = 5.5 × 1013 cm2; as well as [Formula: see text], the effective quenching cross section. The excitation transfer cross sections which are considered accurate to within ±20% are in the ratio predicted by the principle of detailed balancing.
Sensitized fluorescence in cesium vapor induced by collisions with excited rubidium atoms was investigated in order to determine the total cross sections for inelastic collisions between excited rubidium atoms and cesium atoms in their ground states. The partial pressure of the rubidium vapor in the Rb–Cs mixture was kept below 2 × 10−5 mm Hg in order to eliminate effects due to the trapping of the Rb resonance radiation. The collision cross sections for the various excitation transfer processes are as follows: Q12′(Rb 5 2P1/2 → Cs 6 2P3/2) = 1.5 Å2; Q11′(Rb 5 2P1/2 → Cs 6 2P1/2) = 0.5 Å2; Q22′(Rb 5 2P3/2 → Cs 6 2P3/2) = 0.9 Å2; Q21′(Rb 5 2P3/2 → Cs 6 2P1/2) = 0.3 Å2. The fact that the cross sections are considerably smaller than those for collisions between similar atoms indicates that the Rb–Cs interactions probably involve van der Waals' forces with a much shorter range than exchange forces, which play a dominant role in Rb–Rb or Cs–Cs collisions.
The Rb(5D,7S)+H2→RbH+H photochemical reaction has been studied.The RbH molecules are formed in three-body reactive collisions between exited 5D or 7S atoms and ground state H2 molecules.Using two-photon absorption.Rb vapor mixed with Hz gas was irradiated in a glass fluorescence cell with pulses of 778.2nm or 760.1nm radiation from a YAG laser pumped OPO laser,populating one of the 5D and 7S states by two-photon absorption.The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated.The measured fluorescent intensities are proportional to the products of the appropriate population.The rate equations were solved.We estimated the value of cross sections for collisional energy transfer from Rb(5D) to Rb(7S), from Rb(7S)to Rb(5D) to be (6.9±1.4)×10-17 and(2.1±0.4)×10-16 cm2,respectively.The cross sections for reactive collisions Rb(5D)+H2RbH+H and Rb(7S)+H2→RbH+H are (4.3±1.1)×10-17 and(5.8±1.5)×10-17 cm2,respectively.The relative reactivity with H2 for two studied atoms is in an order of Rb(7S)Rb(5D).