A novel apparatus has been developed in which atoms in a magneto-optical trap are used as targets in ion-atom collision experiments. The apparatus is an extension of earlier methodology in which the momentum of the recoiling target is measured and used to deduce the collision Q value and projectile scattering angle. In the present work, the low temperature of the target atoms yields increased momentum resolution, which in turn leads to improved Q value and scattering angle resolution. In addition, because the trapping process leaves some fraction of the atoms in an excited state, the new methodology is ideal for the study of collisions with excited targets. The prototypical system presented is low energy charge transfer between singly charged alkali ions and trapped rubidium atoms in the ground and first excited state.A novel apparatus has been developed in which atoms in a magneto-optical trap are used as targets in ion-atom collision experiments. The apparatus is an extension of earlier methodology in which the momentum of the recoiling target is measured and used to deduce the collision Q value and projectile scattering angle. In the present work, the low temperature of the target atoms yields increased momentum resolution, which in turn leads to improved Q value and scattering angle resolution. In addition, because the trapping process leaves some fraction of the atoms in an excited state, the new methodology is ideal for the study of collisions with excited targets. The prototypical system presented is low energy charge transfer between singly charged alkali ions and trapped rubidium atoms in the ground and first excited state.

Review of Scientific InstrumentsJul 28, 200424 citations

Collision ionization of excited states of rubidium

M. Chéret, Annie Spielfiedel, Richard R. Durand +1 more

Jan 1, 19800 citations

Efficient collisional dissociation of Na{sub 2}{sup +} by laser-excited Na (3p)

Charles Tapalian, W. W. Smith

In studying ionization reactions in a single dense effusive beam of laser-excited Na(3p) atoms, we observe production of both Na{sub 2}{sup +} and Na{sup +} ions. The Na{sup +} results from the familiar associative ionization reaction of two Na(3p) atoms and the Na{sup +} ions under our conditions result mostly from the collisional dissociation of the Na{sub 2}{sup +} by reaction with a third excited Na(3p) atom, rather than from photo- dissociation or photoionization. A CW, single-frequency dye laser tuned to 589 nm resonantly excites the Na(3s) atoms to the 3p state. The atomic beam Na(3s) density is determined from low-intensity 589 absorption measurements. Na{sup +} ion yield depends on the cube of the Na beam density, suggesting successive collisions of three Na(3p) atoms: we believe the Na{sub 2}{sup +} ions polarize the third Na(3p) atom, resulting in a R{sup -4} orbiting collision interaction. A large collisional dissociation cross-section of approximately (4{plus_minus}2)x10{sup -13} cm{sup 2} results, for oven temperatures in the 500-600K range.In studying ionization reactions in a single dense effusive beam of laser-excited Na(3p) atoms, we observe production of both Na{sub 2}{sup +} and Na{sup +} ions. The Na{sup +} results from the familiar associative ionization reaction of two Na(3p) atoms and the Na{sup +} ions under our conditions result mostly from the collisional dissociation of the Na{sub 2}{sup +} by reaction with a third excited Na(3p) atom, rather than from photo- dissociation or photoionization. A CW, single-frequency dye laser tuned to 589 nm resonantly excites the Na(3s) atoms to the 3p state. The atomic beam Na(3s) density is determined from low-intensity 589 absorption measurements. Na{sup +} ion yield depends on the cube of the Na beam density, suggesting successive collisions of three Na(3p) atoms: we believe the Na{sub 2}{sup +} ions polarize the third Na(3p) atom, resulting in a R{sup -4} orbiting collision interaction. A large collisional dissociation cross-section of approximately (4{plus_minus}2)x10{sup -13} cm{sup 2} results, for oven temperatures in the 500-600K range.

Bulletin of the American Physical SocietyMay 1, 19930 citations

Formation and mean lifetime of the metastable doubly charged rare-gas dimer NeAr2+

I. Ben-Itzhak, Ilya Gertner, B. Rosner

The observation of a long-lived ${\mathrm{NeAr}}^{2+}$ molecular ion is reported. This ion was obtained by charge stripping of a 900-keV ${\mathrm{NeAr}}^{+}$ beam in an Ar gas target, and its mean lifetime was determined to be 275\ifmmode\pm\else\textpm\fi{}25 nsec. This is a direct measurement of the mean lifetime of a doubly charged rare-gas dimer. The ion decay is decribed well by a single exponential decay, suggesting that only one metastable state is populated in the collision. The cross section for the ${\mathrm{NeAr}}^{2+}$ production was determined to be (3\ifmmode\pm\else\textpm\fi{}2)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$ ${\mathrm{cm}}^{2}$ . The existence of this weakly bound molecular ion and the fact that its mean lifetime is known can serve to motivate better theoretical calculations of molecular structure and the dissociation process.The observation of a long-lived ${\mathrm{NeAr}}^{2+}$ molecular ion is reported. This ion was obtained by charge stripping of a 900-keV ${\mathrm{NeAr}}^{+}$ beam in an Ar gas target, and its mean lifetime was determined to be 275\ifmmode\pm\else\textpm\fi{}25 nsec. This is a direct measurement of the mean lifetime of a doubly charged rare-gas dimer. The ion decay is decribed well by a single exponential decay, suggesting that only one metastable state is populated in the collision. The cross section for the ${\mathrm{NeAr}}^{2+}$ production was determined to be (3\ifmmode\pm\else\textpm\fi{}2)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$ ${\mathrm{cm}}^{2}$. The existence of this weakly bound molecular ion and the fact that its mean lifetime is known can serve to motivate better theoretical calculations of molecular structure and the dissociation process.

Physical Review AJan 1, 199316 citations

The observation of a long-lived

{\mathrm{NeAr}}^{2+}

molecular ion is reported. This ion was obtained by charge stripping of a 900-keV

{\mathrm{NeAr}}^{+}

beam in an Ar gas target, and its mean lifetime was determined to be 275\ifmmode\pm\else\textpm\fi{}25 nsec. This is a direct measurement of the mean lifetime of a doubly charged rare-gas dimer. The ion decay is decribed well by a single exponential decay, suggesting that only one metastable state is populated in the collision. The cross section for the

{\mathrm{NeAr}}^{2+}

production was determined to be (3\ifmmode\pm\else\textpm\fi{}2)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}18}$

{\mathrm{cm}}^{2}

. The existence of this weakly bound molecular ion and the fact that its mean lifetime is known can serve to motivate better theoretical calculations of molecular structure and the dissociation process.