As a further theoretical study of the collision-induced quantum interference on rotational energy transfer in an atom-diatom system, the differential interference angles for singlet-triplet mixed states of Na 2 system in collision with He were calculated based on the first-Born approximation of time-dependent perturbation theory, taking into account the anisotropic Lennard-Jones interaction potential and the long-range interaction poten- tial. The relationships of differential interference angle versus impact parameter including collision parameter, velocity, are obtained. It is beneficial to reducing the loss in molecular cooling and trapping.As a further theoretical study of the collision-induced quantum interference on rotational energy transfer in an atom-diatom system, the differential interference angles for singlet-triplet mixed states of Na 2 system in collision with He were calculated based on the first-Born approximation of time-dependent perturbation theory, taking into account the anisotropic Lennard-Jones interaction potential and the long-range interaction poten- tial. The relationships of differential interference angle versus impact parameter including collision parameter, velocity, are obtained. It is beneficial to reducing the loss in molecular cooling and trapping.

The Journal of Atomic and Molecular SciencesJan 1, 20101 citation

Low-temperature collisions of Na2 with He

Wang Yue, Dong De-Zhi, Weiyan Li +3 more

The close coupling calculation of rotationally inelastic collision of He with Na2 is first performed by employing a recently computed ab initio potential energy surface. The process of rovibrational energy excitation and relaxation of Na2 in collision with He has been studied in detail based on the single and double exitations coupled cluster with a noniterative perturbation treatment of triple excitations CCSD （T） potential energy surface. Our results are in good agreement with the experimental results. Our results show that: （1）The elastic cross section（Δj=0） is much larger than the inelastic cross section. （2）The largest amplitude occurs at small scattering angles. At low Δj transition, the He projectile is predominantly forward scattering. Backward scattering occurs as Δj increases. （3）For inelastic cross section, the most effective transition is that with Δj=2.（4）The fast narrow diffraction oscillations in the cross sections are the obvious characteristics for the low Δj inelastic transitions, which decreases with increasing j. （5）The elastic differential-cross-sections（DCS）provides a useful visualization of rotational rainbows at low translational energy. It is beneficial to reducing the loss in molecular cooling and trapping.The close coupling calculation of rotationally inelastic collision of He with Na2 is first performed by employing a recently computed ab initio potential energy surface. The process of rovibrational energy excitation and relaxation of Na2 in collision with He has been studied in detail based on the single and double exitations coupled cluster with a noniterative perturbation treatment of triple excitations CCSD （T） potential energy surface. Our results are in good agreement with the experimental results. Our results show that: （1）The elastic cross section（Δj=0） is much larger than the inelastic cross section. （2）The largest amplitude occurs at small scattering angles. At low Δj transition, the He projectile is predominantly forward scattering. Backward scattering occurs as Δj increases. （3）For inelastic cross section, the most effective transition is that with Δj=2.（4）The fast narrow diffraction oscillations in the cross sections are the obvious characteristics for the low Δj inelastic transitions, which decreases with increasing j. （5）The elastic differential-cross-sections（DCS）provides a useful visualization of rotational rainbows at low translational energy. It is beneficial to reducing the loss in molecular cooling and trapping.

Acta Physica SinicaJan 1, 20091 citation

Inelastic Collisions of Slow Atoms

J. Callaway, Ernest Bauer

A general approximate method for computing the cross sections for certain inelastic collision processes is developed. It is based on the possibility of obtaining, with the use of the impact-parameter method, an exact expression for the transition amplitude in a special case. The dependence of the cross section on the parameters of coupling constant, velocity, and energy difference between states is discussed for a two-level model. Detailed calculations are made of cross section for collisions of the type $A(^{2}P_{\frac{3}{2}})+B\ensuremath{\rightleftharpoons}A(^{2}P_{\frac{1}{2}})+B$, where $A$ is an excited atom of an alkali metal and $B$ is an atom of a noble gas. An Appendix contains a review of the effective long-range interaction of atoms.A general approximate method for computing the cross sections for certain inelastic collision processes is developed. It is based on the possibility of obtaining, with the use of the impact-parameter method, an exact expression for the transition amplitude in a special case. The dependence of the cross section on the parameters of coupling constant, velocity, and energy difference between states is discussed for a two-level model. Detailed calculations are made of cross section for collisions of the type $A(^{2}P_{\frac{3}{2}})+B\ensuremath{\rightleftharpoons}A(^{2}P_{\frac{1}{2}})+B$, where $A$ is an excited atom of an alkali metal and $B$ is an atom of a noble gas. An Appendix contains a review of the effective long-range interaction of atoms.

Physical ReviewNov 15, 1965134 citations

Inelastic collisions between excited sodium atoms and molecules.

M. Stupavsky

P^2P3/2 m ^-x^n8 *n sodium vapour, induced by inelastic collisions with the diatomic molecules HD, and N^, was studied using techniques of sensitized fluorescence.The mixtures of sodium vapour with the various molecular gases were irradiated with one component of the appropriate resonance doublet.The fluorescence which contained both components of the doublet, was monitored at right angles to the direction of excitation.The measurement of the relative intensities of the fluorescent components 2 yielded the total inelastic cross sections for P mixing, Ql2(2Pi/2---> 2p3/2^ and ^21^2pi/2^---' 2p3/2^* The sodium vaPour *n 5. Cross Sections for 3 P. ---3 P. Mixing Induced by Sodium Molecule Collisions.38 6. Cross Sections for Excitation Transfer in Na-Molecule Collisions, together with the Corresponding Relative Velocity of the Colliding Partners 42 2 2 7. Comparison of the Cross Sections for P. ---^-s/o Mixing Induced by Alkali Atom-Molecule Collisions 43 viP^2P3/2 m ^-x^n8 *n sodium vapour, induced by inelastic collisions with the diatomic molecules HD, and N^, was studied using techniques of sensitized fluorescence.The mixtures of sodium vapour with the various molecular gases were irradiated with one component of the appropriate resonance doublet.The fluorescence which contained both components of the doublet, was monitored at right angles to the direction of excitation.The measurement of the relative intensities of the fluorescent components 2 yielded the total inelastic cross sections for P mixing, Ql2(2Pi/2---> 2p3/2^ and ^21^2pi/2^---' 2p3/2^* The sodium vaPour *n 5. Cross Sections for 3 P. ---3 P. Mixing Induced by Sodium Molecule Collisions.38 6. Cross Sections for Excitation Transfer in Na-Molecule Collisions, together with the Corresponding Relative Velocity of the Colliding Partners 42 2 2 7. Comparison of the Cross Sections for P. ---^-s/o Mixing Induced by Alkali Atom-Molecule Collisions 43 vi

Jan 1, 19680 citations

Cold collisions between atoms and diatomic molecules

Marius Lysebo, Leif Veseth

Collision cross sections are calculated for the three systems ${\text{O}}_{2}\text{-He}$ , ${\text{Na}}_{2}\text{-Na}$ and ${\text{K}}_{2}\text{-K}$ at cold and ultracold temperatures. We discuss their relevance for cold molecule formation by buffer-gas cooling and by other cooling methods where collisions between molecules and atoms are important, e.g photoassociation. The molecule is treated as a rigid rotator in the electronic and vibrational ground state. We have calculated ab initio the potential energy surfaces for the three systems with special emphasis on the long range potential which is very important at low energies. With relevance to buffer gas cooling, we have also studied the thermalization process between ${\text{O}}_{2}$ molecules and He atoms as determined by the calculated cross sections.Collision cross sections are calculated for the three systems ${\text{O}}_{2}\text{-He}$, ${\text{Na}}_{2}\text{-Na}$ and ${\text{K}}_{2}\text{-K}$ at cold and ultracold temperatures. We discuss their relevance for cold molecule formation by buffer-gas cooling and by other cooling methods where collisions between molecules and atoms are important, e.g photoassociation. The molecule is treated as a rigid rotator in the electronic and vibrational ground state. We have calculated ab initio the potential energy surfaces for the three systems with special emphasis on the long range potential which is very important at low energies. With relevance to buffer gas cooling, we have also studied the thermalization process between ${\text{O}}_{2}$ molecules and He atoms as determined by the calculated cross sections.

Physical Review AMar 24, 200815 citations

Evidence for hybrid classical - quantal behaviour in state- and angle-resolved atom - diatom scattering

Anthony J. McCaffery, Ruth J. Wilson

We present measurements of the state-to-state differential scattering cross section (DCS) for X 16Cg Na2 with Xe using a new sub-Doppler spectroscopic method and compare results with those obtained using molecular beam techniques on the same system; the agreement is good. Criteria for comparison are based on the recent finding (McCaffery A J and Wilson R J 1996 Phys. Rev. Lett. 77 48) that simple quasiclassical vector relations determine the direction of the initial relative velocity vector and the scattering angle. The incident velocity direction is such that the perpendicular component just opens the inelastic channel and the parallel component is scattered. The relationship is Newtonian but is modified by the molecule’s characteristic quantum structure. Angular distributions from a range of experiments are found to obey the vector relation, suggesting that atom–molecule collisions are controlled by a quantum-modified Newtonian mechanics, the modification arising as a consequence of the internal energy level structure of the molecule. We introduce the term quantum-constrained kinematics to describe the hybrid mechanics and suggest that this may also influence other collisional events.We present measurements of the state-to-state differential scattering cross section (DCS) for X 16Cg Na2 with Xe using a new sub-Doppler spectroscopic method and compare results with those obtained using molecular beam techniques on the same system; the agreement is good. Criteria for comparison are based on the recent finding (McCaffery A J and Wilson R J 1996 Phys. Rev. Lett. 77 48) that simple quasiclassical vector relations determine the direction of the initial relative velocity vector and the scattering angle. The incident velocity direction is such that the perpendicular component just opens the inelastic channel and the parallel component is scattered. The relationship is Newtonian but is modified by the molecule’s characteristic quantum structure. Angular distributions from a range of experiments are found to obey the vector relation, suggesting that atom–molecule collisions are controlled by a quantum-modified Newtonian mechanics, the modification arising as a consequence of the internal energy level structure of the molecule. We introduce the term quantum-constrained kinematics to describe the hybrid mechanics and suggest that this may also influence other collisional events.

Journal of Physics B Atomic Molecular and Optical PhysicsDec 28, 199722 citations

A

is an excited atom of an alkali metal and

B

is an atom of a noble gas. An Appendix contains a review of the effective long-range interaction of atoms.

Collision cross sections are calculated for the three systems

{\text{O}}_{2}\text{-He}

{\text{Na}}_{2}\text{-Na}

and

{\text{K}}_{2}\text{-K}

at cold and ultracold temperatures. We discuss their relevance for cold molecule formation by buffer-gas cooling and by other cooling methods where collisions between molecules and atoms are important, e.g photoassociation. The molecule is treated as a rigid rotator in the electronic and vibrational ground state. We have calculated ab initio the potential energy surfaces for the three systems with special emphasis on the long range potential which is very important at low energies. With relevance to buffer gas cooling, we have also studied the thermalization process between

{\text{O}}_{2}

molecules and He atoms as determined by the calculated cross sections.