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光谱学与光谱分析

Photodissociation of the Excited RbHe(Ar) States

Shen Yi

Published Jan 1, 2002• 0 citations
OpenAlex

Abstract

We report here an experimental study of the process Rb(5 2 P )+He(Ar)+ nhν →Rb(7 2 D )+He(Ar)+( n -1) hν ,where nhν represents a radiation field of frequency ν having n photons.The frequency ν is tuned in the blue wing of the Rb7 D 5/2 →5 P 3/2 transition.The branching ratios are defined as the ratios of 7 D 3/2 to 7 D 5/2 fluorescence.The ratios are determined for detuning ranging from about 100 cm -1 in the blue wing of the Rb7 D 5/2 .The measurements show a strong sensitivity to the interatomic potentials and to nonadiabatic effects in the dissociation dynamics.

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[Measurement of fine-structure branching ratios for Rb-He optical collisions].

Lei Lü, Lin Li, Yu-Hua Deng +3 more

Experimental ratios of branching in the fine-structure levels of the Rb5P multiplet, as a consequence of an optical collision with He, are reported. The process studied is Rb(5S1/2 )+ He + hrv --> Rb(5P(J)) +He, where the pulsed laser frequency v is tuned in the wings of the Rb resonance transitions. The authors defined the detuning delta to be v-v (D2 )(delta > 0) for laser frequency v highter than that of RbD2 transition and to be v-v (D1)(delta < 0) for v lower than the RbD1 transition. As RbHe molecular states are correlated to the two 5 2P(J) states, there is some likelihood that the molecule will dissociate into 5 2P1/2 or 5P3/2 state. The dissociation results in a nonuniform distribution of atomic Rb5P(J) states. The branching ratios are defined as n1/n2, where n1 and n2 are densities of the 5P1/2 and 5P3/2 states dissociated. To determine experimentally the relative cross section for scattering into the two fine-structure states, the relative time-intergrated intensities of the resulting Rb emission lines, I(5P3/2 --> 5P1/2 )[I(D2)] and I(5P1/2 --> 5P3/2) ) [I(D1)], were measured. The ratios are determined by detunings from about 200 cm(-1) in the blue wing to -180 cm(-1) in the red wing of the Rb5P multiplet. A rate equation analysis of the pressure dependence was yielded. The branching ratios and cross sections for collisional 5P1/2 --> 5P3/2 transition were obtained from the slope and intercept. The blue-wing branching ratios show a detuning-dependent approach to limit of 0. 2. The branching was found to be very large (-40) in the red wing, irrespective of the detuning. Fine structure changing cross section (1.1 +/- 0.3) x 10(-17) cm2 was measured from wing excitation, and the result is consistent with the cross section obtained from resonant excitation of the Rb5P(J) state. The measurements show a strong sensitivity to interatomic potentials and to nonadiabatic effects in dissociation dynamics.

•Jul 1, 2009•0 citations

Photodissociation of Cs_2 molecules and collisional energy transfer

Yifan Shen

Population of the 6~2D state of Cs atoms by photodissociation of Cs_2 molecules through the use of the fixed frequency line 441.6 nm of a He-Cd~+ laser radiation is produced. Combining ratio of atomic to molecular fluorescence, the ratio of collisional rate coefficient to predissociation rate is estimated to be 9.6×10~(-18) cm~3. The branching ratio is defined as the ratio of 6D_(3/2) to 6D_(5/2) fluorescence. The branching is determined in the Cs density range between 1 and 9×10~(15) cm~(-3). The ratio of the dissociation rates produced in the Cs 6~2D fine-structure states is 0.41. Fine-structure changing cross section has been measured for wing excitation, the result is consistent with cross section obtained from resonant excitation of the 6~2D states.

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Experimental fine-structure branching ratio for R b -A r optical collision

Yifan Shen, A Pulati, Silayi Huerxida

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.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 8, 1999•0 citations

Experimental fine-structure branching ratios for Na-rare gas optical collisions

Mark D. Havey, F. T. Delahanty, Linda L. Vahala +1 more

Experimental ratios for branching into the fine‐structure levels of the Na 3p multiplet, as a consequence of an optical collision with He, Ne, Ar, Kr, or Xe, are reported. The process studied is Na(3s2S1/2) +RG+nhν → Na(3p2 Pj)+RG+(n−1)hν, where RG represents a rare gas atom and where the laser frequency ν is tuned in the wings of the Na resonance transitions. The branching ratios are defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Na D1 and D2 lines. The ratios are determined for detunings ranging from about 650 cm−1 blue to 170 cm−1 red of the Na 3p multiplet. The branching is found to be strongly detuning dependent in the vicinity of the NaKr and NaXe near red‐wing satellites. The blue wing branching ratios show a detuning‐dependent approach to a recoil or sudden statistical limit of 0.5, irrespective of the rare gas.

AIP conference proceedings•Jan 1, 1986•0 citations

[Experimental investigation of mechanisms of forming RbH by irradiating a Rb+H2 mixture with laser light].

Xiaoyan Shen, Jing Liu, Kang Dai +1 more

The radiation of a laser photoexcited Rb atoms from the ground state to the 5P3/2 level in a mixture of Rb vapor and hydrogen. The energy-pooling collision 5P3/2 + 5P3/2 --> 5S1/2 + 5D producted 5D state. The Rb (5P3/2) density and spatial distribution were mapped by monitoring the absorption of a counter-propagating laser beam, tuned to the 5P3/2 --> 7S1/2 transition, which could be translated parallel to the pump beam. In the presence of radiation trapping, the spontaneous radiation rate is multiplied by the transmission factor T5P3/2 --> 5S1/2, which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed. The T5P3/2 --> 5S1/2 is related to the frequency dependent absorption cross section and the density and spatial distribution of atoms in the level of the transition. The effective radiative rates of the Rb D2 line as a function of the H2 pressure were obtained. These quantities were combined with the measured excited atom density and fluorescence ratio to yield absolute energy-pooling rate coefficient. The quenching collision Rb (5P3/2) + H2 (v = 0) --> Rb(5S) + H2 (v = 2) producted state H2 (v= 2). This process is at least 16 times faster than the Rb (5P3/2) radiative decay rate. The reverse process of this process is relatively unlikely due to their large translational energy defect. The cross section for the process H2 (v = 2) + H2 (v = 0) --> H2 (vn = 1) + H2 (v = 0) + 3 920.2 cm(-1) is 7.7 x 10(-19) cm2. Hence the relaxation rate of this vibrational level is relatively slow and the nuclear spin statistics is conserved. The H2 (v = 2) density was determined by using the cross section for Rb (5P3/2)-H2 quenching. RbH was fromed by the Rb(5D) + H2 and Rb (5P3/2) + H2 (v = 2) reactions and observed by laser absorption. The ratio of 5D --> 5P3/2 to 5P3/2 --> 5S1/2 fluorescence was measured as a function of the H2 density. The absorption of the laser beam tuned to the X1sigma+ --> A1sigma+ line of RbH was also measured as a function of the H2 density. From these measurements we obtained the cross section of 4.02 x 10(-7) cm2 for the process Rb (5D) + H2 --> RbH + H. The cross section for Rb (5P3/2) + H2 (upsilon = 2) --> RbH + H is 1.00 x 10(-8) cm2. This experiment showed that under our experimental conditions, RbH molecules are not created by a direct interaction of Rb(5P) with H2 but through a two-step reaction.

•Nov 1, 2008•0 citations

Experimental fine-structure branching ratios for Na–rare-gas optical collisions

Mark D. Havey, F. T. Delahanty, Linda L. Vahala +1 more

Experimental ratios for branching into the fine-structure levels of the Na 3p multiplet, as a consequence of an optical collision with He, Ne, Ar, Kr, or Xe, are reported. The process studied is Na(3s $^{2}S_{1/2}$)+scrR+nh\ensuremath{\nu}\ensuremath{\rightarrow} Na(3p $^{2}P_{j}$)+scrR+(n-1)h\ensuremath{\nu} , where scrR represents a rare-gas atom and where the laser frequency \ensuremath{\nu} is tuned in the wings of the Na resonance transitions. The branching ratios are defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Na D1 and D2 lines. The ratios are determined for detunings ranging from about 650 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the blue wing to 170 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the red wing of the Na 3p multiplet. The branching is found to be strongly detuning dependent in the vicinity of the NaAr, NaKr, and NaXe near-red-wing satellites. The blue-wing branching ratios show a detuning-dependent approach to a recoil, or sudden statistical, limit of 0.5, irrespective of the rare gas. Fine-structure changing cross sections have also been measured for resonant excitation of the Na 3p $^{2}P_{j}$ state; the results are consistent with cross sections obtained from wing excitation.

Physical Review A•Oct 1, 1986•21 citations
We report here an experimental study of the process Rb(5 2 P )+He(Ar)+ nhν →Rb(7 2 D )+He(Ar)+( n -1) hν ,where nhν represents a radiation field of frequency ν having n photons.The frequency ν is tuned in the blue wing of the Rb7 D 5/2 →5 P 3/2 transition.The branching ratios are defined as the ratios of 7 D 3/2 to 7 D 5/2 fluorescence.The ratios are determined for detuning ranging from about 100 cm -1 in the blue wing of the Rb7 D 5/2 .The measurements show a strong sensitivity to the interatomic potentials and to nonadiabatic effects in the dissociation dynamics.
Experimental ratios of branching in the fine-structure levels of the Rb5P multiplet, as a consequence of an optical collision with He, are reported. The process studied is Rb(5S1/2 )+ He + hrv --> Rb(5P(J)) +He, where the pulsed laser frequency v is tuned in the wings of the Rb resonance transitions. The authors defined the detuning delta to be v-v (D2 )(delta > 0) for laser frequency v highter than that of RbD2 transition and to be v-v (D1)(delta < 0) for v lower than the RbD1 transition. As RbHe molecular states are correlated to the two 5 2P(J) states, there is some likelihood that the molecule will dissociate into 5 2P1/2 or 5P3/2 state. The dissociation results in a nonuniform distribution of atomic Rb5P(J) states. The branching ratios are defined as n1/n2, where n1 and n2 are densities of the 5P1/2 and 5P3/2 states dissociated. To determine experimentally the relative cross section for scattering into the two fine-structure states, the relative time-intergrated intensities of the resulting Rb emission lines, I(5P3/2 --> 5P1/2 )[I(D2)] and I(5P1/2 --> 5P3/2) ) [I(D1)], were measured. The ratios are determined by detunings from about 200 cm(-1) in the blue wing to -180 cm(-1) in the red wing of the Rb5P multiplet. A rate equation analysis of the pressure dependence was yielded. The branching ratios and cross sections for collisional 5P1/2 --> 5P3/2 transition were obtained from the slope and intercept. The blue-wing branching ratios show a detuning-dependent approach to limit of 0. 2. The branching was found to be very large (-40) in the red wing, irrespective of the detuning. Fine structure changing cross section (1.1 +/- 0.3) x 10(-17) cm2 was measured from wing excitation, and the result is consistent with the cross section obtained from resonant excitation of the Rb5P(J) state. The measurements show a strong sensitivity to interatomic potentials and to nonadiabatic effects in dissociation dynamics.
Population of the 6~2D state of Cs atoms by photodissociation of Cs_2 molecules through the use of the fixed frequency line 441.6 nm of a He-Cd~+ laser radiation is produced. Combining ratio of atomic to molecular fluorescence, the ratio of collisional rate coefficient to predissociation rate is estimated to be 9.6×10~(-18) cm~3. The branching ratio is defined as the ratio of 6D_(3/2) to 6D_(5/2) fluorescence. The branching is determined in the Cs density range between 1 and 9×10~(15) cm~(-3). The ratio of the dissociation rates produced in the Cs 6~2D fine-structure states is 0.41. Fine-structure changing cross section has been measured for wing excitation, the result is consistent with cross section obtained from resonant excitation of the 6~2D states.
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.
Experimental ratios for branching into the fine‐structure levels of the Na 3p multiplet, as a consequence of an optical collision with He, Ne, Ar, Kr, or Xe, are reported. The process studied is Na(3s2S1/2) +RG+nhν → Na(3p2 Pj)+RG+(n−1)hν, where RG represents a rare gas atom and where the laser frequency ν is tuned in the wings of the Na resonance transitions. The branching ratios are defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Na D1 and D2 lines. The ratios are determined for detunings ranging from about 650 cm−1 blue to 170 cm−1 red of the Na 3p multiplet. The branching is found to be strongly detuning dependent in the vicinity of the NaKr and NaXe near red‐wing satellites. The blue wing branching ratios show a detuning‐dependent approach to a recoil or sudden statistical limit of 0.5, irrespective of the rare gas.
The radiation of a laser photoexcited Rb atoms from the ground state to the 5P3/2 level in a mixture of Rb vapor and hydrogen. The energy-pooling collision 5P3/2 + 5P3/2 --> 5S1/2 + 5D producted 5D state. The Rb (5P3/2) density and spatial distribution were mapped by monitoring the absorption of a counter-propagating laser beam, tuned to the 5P3/2 --> 7S1/2 transition, which could be translated parallel to the pump beam. In the presence of radiation trapping, the spontaneous radiation rate is multiplied by the transmission factor T5P3/2 --> 5S1/2, which describes the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed. The T5P3/2 --> 5S1/2 is related to the frequency dependent absorption cross section and the density and spatial distribution of atoms in the level of the transition. The effective radiative rates of the Rb D2 line as a function of the H2 pressure were obtained. These quantities were combined with the measured excited atom density and fluorescence ratio to yield absolute energy-pooling rate coefficient. The quenching collision Rb (5P3/2) + H2 (v = 0) --> Rb(5S) + H2 (v = 2) producted state H2 (v= 2). This process is at least 16 times faster than the Rb (5P3/2) radiative decay rate. The reverse process of this process is relatively unlikely due to their large translational energy defect. The cross section for the process H2 (v = 2) + H2 (v = 0) --> H2 (vn = 1) + H2 (v = 0) + 3 920.2 cm(-1) is 7.7 x 10(-19) cm2. Hence the relaxation rate of this vibrational level is relatively slow and the nuclear spin statistics is conserved. The H2 (v = 2) density was determined by using the cross section for Rb (5P3/2)-H2 quenching. RbH was fromed by the Rb(5D) + H2 and Rb (5P3/2) + H2 (v = 2) reactions and observed by laser absorption. The ratio of 5D --> 5P3/2 to 5P3/2 --> 5S1/2 fluorescence was measured as a function of the H2 density. The absorption of the laser beam tuned to the X1sigma+ --> A1sigma+ line of RbH was also measured as a function of the H2 density. From these measurements we obtained the cross section of 4.02 x 10(-7) cm2 for the process Rb (5D) + H2 --> RbH + H. The cross section for Rb (5P3/2) + H2 (upsilon = 2) --> RbH + H is 1.00 x 10(-8) cm2. This experiment showed that under our experimental conditions, RbH molecules are not created by a direct interaction of Rb(5P) with H2 but through a two-step reaction.
Experimental ratios for branching into the fine-structure levels of the Na 3p multiplet, as a consequence of an optical collision with He, Ne, Ar, Kr, or Xe, are reported. The process studied is Na(3s 2S1/2^{2}S_{1/2}2S1/2​)+scrR+nh\ensuremath{\nu}\ensuremath{\rightarrow} Na(3p 2Pj^{2}P_{j}2Pj​)+scrR+(n-1)h\ensuremath{\nu} , where scrR represents a rare-gas atom and where the laser frequency \ensuremath{\nu} is tuned in the wings of the Na resonance transitions. The branching ratios are defined as I(D1)/I(D2) where I(D1) and I(D2) are measured intensities of the atomic Na D1 and D2 lines. The ratios are determined for detunings ranging from about 650 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the blue wing to 170 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the red wing of the Na 3p multiplet. The branching is found to be strongly detuning dependent in the vicinity of the NaAr, NaKr, and NaXe near-red-wing satellites. The blue-wing branching ratios show a detuning-dependent approach to a recoil, or sudden statistical, limit of 0.5, irrespective of the rare gas. Fine-structure changing cross sections have also been measured for resonant excitation of the Na 3p 2Pj^{2}P_{j}2Pj​ state; the results are consistent with cross sections obtained from wing excitation.