Rb atoms were excited to the 5P3/2 level using a single-mode laser diode. The 5P3/2 state atom density was measured by the absorption of line from a Rb hollow-cathode lamp. The excited atom density is combined with measured fluorescence ratio to determine collisional cross section for the energy pooling process [i.e. Rb(5P3/2)+Rb(5P3/2)→Rb(5D)+Rb(5S)]. The cross section is (5.0±1.9)(?)10-14cm2. Cross section for 5P3/2 →5P1/2 transfer in Rb, induced in collision with ground-state Rb atoms, has been determined using methods of atomic fluorescence. The resulting fluorescence included a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state and the energy-pooling collisions. Measurement of relative intensities of the two components yielded the following cross section: σ(5P3/2→5P1/2)=(3.0±0.9)×10-15cm2. It is found that the rate for the energy pooling is an order of magnitude more efficient than 5P3/2→5P1/2 mixture. Comparisons of our result with other experiments have been made.
Experimental ratio for branching into the fine structure levels of the Rb52P multiplet, as a consequence of an optical collision with Ar, is reported. An optically thin gaseous mixture of Rb and low-density Ar is excited by a cw dye laser. The excited RbAr molecule is dissociated into the Rb5P1/2 or Rb5P3/2, the branching ratio is defined as I(D1)/I(D2) where 1(D1) and I(D2) are measured intensities of the atomic RbD1 and D2 lines. The branching is determined for tuning ranging from 600 nm to 570 nm and in the Ar density range 2 to 8 X 1017 cm-3. The ratio of the dissociation rates and the fine structure changing cross section are obtained. The ratio of the dissociation rates approaches 0.7 as a limit which is independent of the laser frequency.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Cross sections for 6^D, 7^D and 8^0 fine-structure mixing in Rb, induced in collisions with various ground-state atoms and N2 molecules, have been determined using methods of atomic fluorescence.Rb vapour, pure or mixed with a buffer gas, was irradiated in a glass fluorescence cell with pulses of radiation from a N2 laser-pumped dye laser, populating a fine-structure state by two-photon absorption.The resulting fluorescence included a direct component emitted in the decay of .the optically excited state and a sensitized component due to the col1isional1y populated fine-structure state.Measure ments of relative intensities of the two components in relation to buffer gas (or Rb vapour) pressure yielded the following cross sections.-14 2 Inelastic Cross sections (10 cm ) process Rb He Ne Ar Kr Xe I would like to express sincere thanks to Professor L.
The collisional energy transfer in Rb(5P_J)+M collisions,where M=Ne,N_2 under gas cell conditions was investigated.For collision with Ne only electronic to translational energy transfer is possible.However,in the N_2 case,electronics to vibrational or rotational transfer is important.The Rb(5P_(3/2))state is excited by a tunable CW diode laser,where the laser is tuned slightly off resonance.The ratio of 5P_(1/2)→5S_(1/2)to the 5P_(3/2)→5S_(1/2) fluorescence as a function of quenching gas pressure was measured.Using a two-state rate equation model the transfer rate coefficients from the Rb(5P_J)state was obtained.The rate coefficient for 5P_(3/2)→5P_(1/2) transfer in collision with Ne is 1.53×10~(-12)cm~3s~(-1).Using the ratio of the 5P_(1/2) to 5P_(3/2) fluorescence for Ne and N_2 case,and fitting the experimental results to the rate equation analysis,we estimate that the rate coefficient for 5P_(3/2)→5P_(1/2) transfer in collision with N_2 is 8.83×10~(-11) cm~3s~(-1).The quenching rate coefficient of the 5P_J state is 1.25×10~(-10) cm~3s~(-1).A qualitative explanation for the results was given.
Cross sections for
72D and
82D fine-structure mixing in Rb, induced by collisions with various ground-state atoms and
N2 molecules, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a buffer gas, was irradiated in a glass fluorescence cell with pulses of radiation from a
N2 laser-pumped dye laser, populating a
2D fine-structure state by two-photon absorption. The resulting fluorescence included a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. Measurements of relative intensities of the two components in relation to buffer-gas pressure yielded the following cross sections (in units of ${10}^{\ensuremath{-}14}$
cm2): $Q({7}^{2}{D}_{\frac{3}{2}}\ensuremath{\rightarrow}{7}^{2}{D}_{\frac{5}{2}})=14.1,15.5,\mathrm{and}10.0$; $Q({7}^{2}{D}_{\frac{3}{2}}\ensuremath{\leftarrow}{7}^{2}{D}_{\frac{5}{2}})=9.0,10.5,\mathrm{and}6.9$, for Kr, Xe, and
N2, respectively; $Q({8}^{2}{D}_{\frac{3}{2}}\ensuremath{\rightarrow}{8}^{2}{D}_{\frac{5}{2}})=8.9,4.9,12.4,24.9,25.8,12.1,\mathrm{and}43.1$; $Q({8}^{2}{D}_{\frac{3}{2}}\ensuremath{\leftarrow}{8}^{2}{D}_{\frac{5}{2}})=5.8,3.2,9.4,15.1,17.6,8.3,\mathrm{and}28.5$, for He, Ne, Ar, Kr, Xe,
N2, and Rb, respectively. Cross sections for the effective depopulation of the
2D states were also determined.
Applying the CW laser absorption and fluorescence method,the cross sections for the fine structure mixing and quenching of the Rb(5P)state,induced by collision with N2 molecules,have been measured.Cesium atoms were optically excited to the 5P3/2 state.The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam,turned to the 5PJ→7S1/2 transitions.The effective radiative rates were calculated for the 5PJ→5S transitions.The fluorescence intensity I794 of the sensitized 5P1/2→5S1/2 emission was measured as a function of N2 density in the range 0.5×1016N4×1016cm-3 at constant temperature T=340 K.It was found that the quantity N/I794 exhibited a parabolic dependence on N,confirming that the quenching of the 5PJ states is due to collision with N2 molecules,not Rb ground state atoms.The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→1/2=(10.43±3.54)×10-16cm2 and σD=(9.8±3.4)×10-16cm2 for the 5PJ fine-structure mixing and quenching,respectively,due to collision with N2 atoms.Our values for these cross sections are in agreement,within combined error bars,with values we have recently obtained under different experimental conditions.