Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Physics B Atomic and Molecular Physics

State-resolved fine-structure transitions in collisions of Ca 4s4p3PJ0with H2and D2molecules

H.‐J. Yuh, Paul J. Dagdigian

Published Nov 14, 1984• 7 citations
Publisher

Abstract

An optical pumping state-selection technique is employed for the measurement of intramultiplet mixing cross sections involving specified spin-orbit states of calcium 4s4p 3PJ0 atoms in collisions with H2 and D2. As was previously found for helium collisions, the J=2 to J'=1 cross sections are found to be the largest of the three possible downward transitions. However, differences in magnitude between the various J to J' cross sections are smaller than for helium. Moreover, the cross sections for the molecular targets are two to three times larger than for the same transitions with helium as the scattering partner. These differences are discussed in terms of the expected dynamics of fine-structure-changing transitions of 3P atoms with atomic and molecular scattering partners.

DOI
10.1088/0022-3700/17/21/024

Related papers

Measurement of cross sections for collisions of the second kind in helium

Joseph S. Bakos, János Szigeti

We have measured the cross sections for collisions of the second kind between helium atoms in the n 1 P ( n = 3,4) state and in the normal state. As a consequence of the collision the atoms are transferred from the n 1 P to the n 1 D, n 3 D or n 3 F state. The n 1 P states were excited selectively by optical pumping. The collision cross sections for the transitions 3 1 P -> 3 1 D, 3 1 P -> 3 3 D, 4 1 P -> 4 1 D, 4 1 P -> 4 3 D and 4 1 P -> 4 3 F were measured as 3.2 × 10 -16 , 2.2 × 10 -19 , 2.8 × 10 -16 , 2.2 × 10 -16 and 9.5 × 10 -17 cm 2 , respectively. Thus they are smaller by several orders of magnitude than those reported previously.

Journal of Physics B Atomic and Molecular Physics•Nov 1, 1968•14 citations

Laser-induced optical pumping measurements of cross sections for fine- and hyperfine-structure transitions in sodium induced by collisions with helium and argon atoms

Chris C. Dobson, Chi C. Sung

Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for $\ensuremath{\Delta}F$ transitions of the ${P}_{3/2}$ state induced by collisions with helium and argon atoms, for a range of values assumed for the ${P}_{1/2}, \ensuremath{\Delta}F$ cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates ${m}_{F}$ measured previously using polarization sensitive absorption. Also, fine-structure transition $(\ensuremath{\Delta}J)$ cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

Physical Review A•May 1, 1999•3 citations

Hyperfine structure transfer, fine structure transfer, and quenching of 113Cd atoms in the 5s5p 3P1 state by collisions with molecular gases

Th. von der Haar, C. Kramer, M. Baumann

Collisions of excited 113Cd(5 3P1) atoms with various molecular gases (N2, H2, D2, CO, CO2, CH4, C2H6, C2H4, O2) have been investigated using atomic fluorescence spectroscopy. By selective excitation of a hyperfine structure level with a pulsed dye laser and studying the time dependence of the fluorescence signals as a function of the buffer gas density the cross sections for quenching, fine structure transfer, and hyperfine structure transfer could be obtained. For N2 molecules the collisions can be described by a decoupling model as has been shown previously for the noble gases as collision partners.

The Journal of Chemical Physics•Feb 1, 1991•7 citations

Electron-atom collision studies using optically state selected beams. Progress report, 1 May 1985-30 April 1986

R. J. Celotta, Michael H. Kelley

Collisions studies using optically state selected beams is discussed. Measurements of spin resolved differential cross sections for superelastic scattering of electrons from excited sodium atoms (3P) are reported. The excited states are prepared by laser optical pumping with circularly polarized light thus giving a pure atomic state before the collision. A crossed beam arrangement of sodium atoms and electrons is used with a scattered electron detector. Scattered electron intensity as a function of scattering angle, incident electron energy, and relative orientation of the incident electronic and atomic spins is measured. 8 refs., 10 figs.

•Jan 1, 1986•0 citations

Fine-structure transitions in Rb(5P) induced by H2and N2molecules

J.‐M. Mestdagh, P de Pujo, J. Cuvellier +3 more

The energy dependence and the absolute value of the cross section for the P 1/2 to P 3/2 fine-structure transition (FST) in Rb(5P) induced by H 2 or N 2 molecules and He atoms has been measured for the first time in a crossed-beam apparatus. The results for He, in excellent agreement with previous experimental data, are used for comparing atomic and molecular target behaviour with regard to FST processes in heavy alkalis. One observes much larger cross sections for H 2 and N 2 at low energies with a much weaker energy dependence. Theoretical work suggests two seemingly competing mechanisms for including large FST cross sections for molecular targets. One, involving an intermediate ionic complex, accounts for the general trend (absolute value and energy dependence) of the experimental data for N 2 while the other, recently suggested by Hickman seems to play the major role when H 2 is the target.

Journal of Physics B Atomic and Molecular Physics•Feb 28, 1982•14 citations

Initial and final orbital alignment probing of the fine-structure-changing collisions among the Ca (4s)1(4p)1, 3P J states with He: determination of coherence and conventional cross-sections

Christopher J. M. Smith, Eileen M. Spain, Mark J. Dalberth +2 more

A laser pump–probe experiment is used to study the orbital alignment effects, orientation effects and vector correlations of collisional transfer of the Ca (4s)1(4p)1, 3P1 state to the Ca (4s)1(4p)1, 3P2, 0 levels. The experiment is configured in a single-collision crossed-beam arrangement between Ca and He, and multi-structure cross-sections are determined using appropriate combinations of linear and circular laser light for the pump/probe steps. Real and imaginary parts of coherence cross-sections are obtained along with the conventional population cross-sections for the m1→m2 magnetic sublevel transitions into the 3P2 level. The total relative cross-section ratio for the perpendicular (m1=±1) to parallel (m1= 0) polarization preparation of 3P1 transferring to 3P2 is 1.46 ± 0.15. For initial 3P1 preparation with laser light linearly polarized perpendicular to the initial relative velocity vector, the transfer into the m2-sublevels of the 3P2 state show a distinct preference for the sign-changing m1=+ 1 →m2=–1 transition. Preparation of Ca 3P1 with laser light linearly polarized parallel to the initial relative velocity vector produces population transfer into the 3P2 level that is completely aligned in the ±1 and ±2 sublevels, consistent with symmetry considerations. The magnitudes of the coherence cross-sections range from a few percent to greater than 100% of some of the population transfer conventional cross-sections. Study of the alignment effect into the final 3P0 state found a very large observed effect (σ|m|= 1/σ|m|= 0) of 23 ± 0.9. Interpretation of the energy transfer results indicates that the energy transfer obeys symmetry rules and follows predictions of curve crossings between the Σ and Π potentials, where for the transfer into 3P2 only indirect coupling can occur.

Journal of the Chemical Society Faraday Transactions•Jan 1, 1993•36 citations
An optical pumping state-selection technique is employed for the measurement of intramultiplet mixing cross sections involving specified spin-orbit states of calcium 4s4p 3PJ0 atoms in collisions with H2 and D2. As was previously found for helium collisions, the J=2 to J'=1 cross sections are found to be the largest of the three possible downward transitions. However, differences in magnitude between the various J to J' cross sections are smaller than for helium. Moreover, the cross sections for the molecular targets are two to three times larger than for the same transitions with helium as the scattering partner. These differences are discussed in terms of the expected dynamics of fine-structure-changing transitions of 3P atoms with atomic and molecular scattering partners.
We have measured the cross sections for collisions of the second kind between helium atoms in the n 1 P ( n = 3,4) state and in the normal state. As a consequence of the collision the atoms are transferred from the n 1 P to the n 1 D, n 3 D or n 3 F state. The n 1 P states were excited selectively by optical pumping. The collision cross sections for the transitions 3 1 P -> 3 1 D, 3 1 P -> 3 3 D, 4 1 P -> 4 1 D, 4 1 P -> 4 3 D and 4 1 P -> 4 3 F were measured as 3.2 × 10 -16 , 2.2 × 10 -19 , 2.8 × 10 -16 , 2.2 × 10 -16 and 9.5 × 10 -17 cm 2 , respectively. Thus they are smaller by several orders of magnitude than those reported previously.
Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for $\ensuremath{\Delta}F$ transitions of the P3/2{P}_{3/2}P3/2​ state induced by collisions with helium and argon atoms, for a range of values assumed for the ${P}_{1/2}, \ensuremath{\Delta}F$ cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates mF{m}_{F}mF​ measured previously using polarization sensitive absorption. Also, fine-structure transition $(\ensuremath{\Delta}J)$ cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.
Collisions of excited 113Cd(5 3P1) atoms with various molecular gases (N2, H2, D2, CO, CO2, CH4, C2H6, C2H4, O2) have been investigated using atomic fluorescence spectroscopy. By selective excitation of a hyperfine structure level with a pulsed dye laser and studying the time dependence of the fluorescence signals as a function of the buffer gas density the cross sections for quenching, fine structure transfer, and hyperfine structure transfer could be obtained. For N2 molecules the collisions can be described by a decoupling model as has been shown previously for the noble gases as collision partners.
Collisions studies using optically state selected beams is discussed. Measurements of spin resolved differential cross sections for superelastic scattering of electrons from excited sodium atoms (3P) are reported. The excited states are prepared by laser optical pumping with circularly polarized light thus giving a pure atomic state before the collision. A crossed beam arrangement of sodium atoms and electrons is used with a scattered electron detector. Scattered electron intensity as a function of scattering angle, incident electron energy, and relative orientation of the incident electronic and atomic spins is measured. 8 refs., 10 figs.
The energy dependence and the absolute value of the cross section for the P 1/2 to P 3/2 fine-structure transition (FST) in Rb(5P) induced by H 2 or N 2 molecules and He atoms has been measured for the first time in a crossed-beam apparatus. The results for He, in excellent agreement with previous experimental data, are used for comparing atomic and molecular target behaviour with regard to FST processes in heavy alkalis. One observes much larger cross sections for H 2 and N 2 at low energies with a much weaker energy dependence. Theoretical work suggests two seemingly competing mechanisms for including large FST cross sections for molecular targets. One, involving an intermediate ionic complex, accounts for the general trend (absolute value and energy dependence) of the experimental data for N 2 while the other, recently suggested by Hickman seems to play the major role when H 2 is the target.
A laser pump–probe experiment is used to study the orbital alignment effects, orientation effects and vector correlations of collisional transfer of the Ca (4s)1(4p)1, 3P1 state to the Ca (4s)1(4p)1, 3P2, 0 levels. The experiment is configured in a single-collision crossed-beam arrangement between Ca and He, and multi-structure cross-sections are determined using appropriate combinations of linear and circular laser light for the pump/probe steps. Real and imaginary parts of coherence cross-sections are obtained along with the conventional population cross-sections for the m1→m2 magnetic sublevel transitions into the 3P2 level. The total relative cross-section ratio for the perpendicular (m1=±1) to parallel (m1= 0) polarization preparation of 3P1 transferring to 3P2 is 1.46 ± 0.15. For initial 3P1 preparation with laser light linearly polarized perpendicular to the initial relative velocity vector, the transfer into the m2-sublevels of the 3P2 state show a distinct preference for the sign-changing m1=+ 1 →m2=–1 transition. Preparation of Ca 3P1 with laser light linearly polarized parallel to the initial relative velocity vector produces population transfer into the 3P2 level that is completely aligned in the ±1 and ±2 sublevels, consistent with symmetry considerations. The magnitudes of the coherence cross-sections range from a few percent to greater than 100% of some of the population transfer conventional cross-sections. Study of the alignment effect into the final 3P0 state found a very large observed effect (σ|m|= 1/σ|m|= 0) of 23 ± 0.9. Interpretation of the energy transfer results indicates that the energy transfer obeys symmetry rules and follows predictions of curve crossings between the Σ and Π potentials, where for the transfer into 3P2 only indirect coupling can occur.