Abstract

Two-photon ionization cross sections from the rubidium ground state have been measured with both a cw 421-nm laser and a combination of cw 421- and 1002-nm lasers. The measurements were performed within a high-vacuum magneto-optical trap while the trapping lasers were switched off, exploiting the long trap lifetime and also the trap laser confinement. The two-photon cross sections were determined for the blue laser near resonance with the 6P1/2 and 6P3/2 states and compared with the estimates of a theoretical model. In near resonance with the 6P states, large two-photon photoionization cross sections were measured.

© 2004 Optical Society of America

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  1. T. P. Dinneen, C. D. Wallace, K. N. Tan, and P. L. Gould, “Use of trapped atoms to measure absolute photoionization cross section,” Opt. Lett. 17, 1706–1708 (1992).
    [CrossRef] [PubMed]
  2. D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
    [CrossRef]
  3. Another important application of work with trap-loss includes molecular spectroscopy, as reviewed in Ref. 4.
  4. F. Masnou-Seeuws and P. Pillet, “Formation of ultracold molecules via photoassociation in a gas of laser cooled atoms,” Adv. At., Mol., Opt. Phys. 47, 53–127 (2001).
    [CrossRef]
  5. J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
    [CrossRef]
  6. J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
    [CrossRef]
  7. In two-color, two-photon ionization, τph represents the time window during which both radiations excite the atoms.
  8. A. A. Radzig and B. M. Smirnov, Reference Data on Atoms, Molecules and Ions (Springer-Verlag, Berlin, 1985).
  9. The present ionization investigation, in which Eq. (2) was used for the evaluation of β(2), operated with Gaussian spatial distributions, as verified by the CCD images of the MOT. In the presence of a non-Gaussian distribution the spatial convolution between the laser and atomic dis-tributions described by β(2) should be evaluated numerically.
  10. P. Lambropoulos, “Theory of multiphoton ionization: near-resonant effects in two-photon ionization,” Phys. Rev. A 9, 1992–2013 (1974).
    [CrossRef]
  11. C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
    [CrossRef] [PubMed]
  12. A longer MOT lifetime was measured while the trapping lasers remained switched on.
  13. P. Lambropoulos and M. R. Teague, “Two-photon ionization with spin–orbit coupling,” J. Phys. B 9, 587–603 (1974).
    [CrossRef]
  14. Michelle Aymar, Laboratoire Aimé Cotton, Unité Propre de Recherches 3321, Campus d’Orsay, Ba⁁t. 505 91405, Orsay Cedex, France (personal communication).

2002

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

2001

F. Masnou-Seeuws and P. Pillet, “Formation of ultracold molecules via photoassociation in a gas of laser cooled atoms,” Adv. At., Mol., Opt. Phys. 47, 53–127 (2001).
[CrossRef]

2000

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

1995

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

1992

1974

P. Lambropoulos and M. R. Teague, “Two-photon ionization with spin–orbit coupling,” J. Phys. B 9, 587–603 (1974).
[CrossRef]

P. Lambropoulos, “Theory of multiphoton ionization: near-resonant effects in two-photon ionization,” Phys. Rev. A 9, 1992–2013 (1974).
[CrossRef]

Anderlini, M.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

Arimondo, E.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Ciampini, D.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Cooper, C. J.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Dalibard, J.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Dinneen, T. P.

Edwards, N. H.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Fazzi, M.

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Foot, C. J.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Fuso, F.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Gould, P. L.

Knize, R. J.

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

Lambropoulos, P.

P. Lambropoulos and M. R. Teague, “Two-photon ionization with spin–orbit coupling,” J. Phys. B 9, 587–603 (1974).
[CrossRef]

P. Lambropoulos, “Theory of multiphoton ionization: near-resonant effects in two-photon ionization,” Phys. Rev. A 9, 1992–2013 (1974).
[CrossRef]

Lowell, J. R.

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

Masnou-Seeuws, F.

F. Masnou-Seeuws and P. Pillet, “Formation of ultracold molecules via photoassociation in a gas of laser cooled atoms,” Adv. At., Mol., Opt. Phys. 47, 53–127 (2001).
[CrossRef]

Morsch, O.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Müller, J. H.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Northup, T.

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

Patterson, B. M.

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

Perrin, H.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Pillet, P.

F. Masnou-Seeuws and P. Pillet, “Formation of ultracold molecules via photoassociation in a gas of laser cooled atoms,” Adv. At., Mol., Opt. Phys. 47, 53–127 (2001).
[CrossRef]

Smirne, G.

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Steane, A. M.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Szriftgiser, P.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Takekoshi, T.

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

Tan, K. N.

Teague, M. R.

P. Lambropoulos and M. R. Teague, “Two-photon ionization with spin–orbit coupling,” J. Phys. B 9, 587–603 (1974).
[CrossRef]

Thomsen, J. W.

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

Townsend, C. G.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Verkerk, P.

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

Wallace, C. D.

Zetie, K. P.

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Adv. At., Mol., Opt. Phys.

F. Masnou-Seeuws and P. Pillet, “Formation of ultracold molecules via photoassociation in a gas of laser cooled atoms,” Adv. At., Mol., Opt. Phys. 47, 53–127 (2001).
[CrossRef]

J. Phys. B

J. H. Müller, D. Ciampini, O. Morsch, G. Smirne, M. Fazzi, P. Verkerk, F. Fuso, and E. Arimondo, “Bose–Einstein condensation of rubidium atoms in a triaxial TOP trap,” J. Phys. B 33, 4095–4105 (2000).
[CrossRef]

P. Lambropoulos and M. R. Teague, “Two-photon ionization with spin–orbit coupling,” J. Phys. B 9, 587–603 (1974).
[CrossRef]

Opt. Lett.

Phys. Rev. A

D. Ciampini, M. Anderlini, J. H. Müller, F. Fuso, O. Morsch, J. W. Thomsen, and E. Arimondo, “Photoionization of ultracold and Bose–Einstein-condensed Rb atoms,” Phys. Rev. A 66, 043409 (2002).
[CrossRef]

J. R. Lowell, T. Northup, B. M. Patterson, T. Takekoshi, and R. J. Knize, “Measurement of the photoionization cross section of the 5S1/2 state of rubidium,” Phys. Rev. A 66, 062704 (2002).
[CrossRef]

P. Lambropoulos, “Theory of multiphoton ionization: near-resonant effects in two-photon ionization,” Phys. Rev. A 9, 1992–2013 (1974).
[CrossRef]

C. G. Townsend, N. H. Edwards, C. J. Cooper, K. P. Zetie, C. J. Foot, A. M. Steane, P. Szriftgiser, H. Perrin, and J. Dalibard, “Phase-space density in the magneto-optical trap,” Phys. Rev. A 52, 1423–1440 (1995).
[CrossRef] [PubMed]

Other

A longer MOT lifetime was measured while the trapping lasers remained switched on.

Michelle Aymar, Laboratoire Aimé Cotton, Unité Propre de Recherches 3321, Campus d’Orsay, Ba⁁t. 505 91405, Orsay Cedex, France (personal communication).

Another important application of work with trap-loss includes molecular spectroscopy, as reviewed in Ref. 4.

In two-color, two-photon ionization, τph represents the time window during which both radiations excite the atoms.

A. A. Radzig and B. M. Smirnov, Reference Data on Atoms, Molecules and Ions (Springer-Verlag, Berlin, 1985).

The present ionization investigation, in which Eq. (2) was used for the evaluation of β(2), operated with Gaussian spatial distributions, as verified by the CCD images of the MOT. In the presence of a non-Gaussian distribution the spatial convolution between the laser and atomic dis-tributions described by β(2) should be evaluated numerically.

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Figures (4)

Fig. 1
Fig. 1

Time decay for the fluorescence of the MOT Rb atoms in the absence (dashed curve) and in the presence (continuous curve) of the 421-nm laser. The ionizing laser, applied in pulses with τph=2 µs and rph=20 kHz, had intensity Iph=48.7 W/cm2 and detuning δ=-16.8±12 MHz from the 5S1/2, F=26P1/2, F=2 transition.

Fig. 2
Fig. 2

Ratio γph/β(2) for one-color, two-photon ionization of the Rb ground state by a 421-nm laser versus laser intensity Iph for laser detunings δ from the 5S1/2, F=26P3/2, F=3 transition at τph=2 µs and rph=20 kHz. Solid curves, results of a fit with a quadratic dependence on the blue laser’s intensity.

Fig. 3
Fig. 3

One-color, two-photon cross sections σ5S(2) for Rb 5S ionization by a 421-nm laser in near resonance with (a) the 6P1/2 intermediate state and (b) the 6P3/2 intermediate state, as functions of laser detuning. Solid curve, results of a numerical simulation without free parameters with the 6pcontinuum dipole moments described in the text.

Fig. 4
Fig. 4

Two-color, two-photon cross sections σ5S(2) for Rb 5S ionization by 421+1002-nm lasers near resonance with the 6P3/2 intermediate state as a function of the blue laser detuning from the 5S1/2, F=26P3/2, F=3 transition. Solid curve, results of a numerical simulation without free parameters with the 6pcontinuum dipole moments described in the text.

Equations (5)

Equations on this page are rendered with MathJax. Learn more.

γph=σ5S(2)β(2)Iphhνph2,
β(2)=1{[1+2(Lx/w0x)2][1+2(Ly/w0y)2]}1/2.
dNdt=-γN-γphN.
N=N0 exp(-γτph)exp(-γphτph).
N(t)=N0 exp(-γt)exp(-γphτphrpht).

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