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D. F. 7. C. 8. U. 6. 1 : Source and simple lens doublet (“Einzellens") 2,5,9,10 : Deflection plates 3,6,8 : Simple lenses. 10. 4. 5. 12. 2. 4 : Wien velocity filter 7 : Deflection quadrupole 11 : Focalisation quadrupole 12 : Deceleration plates 13 : Interaction zone.

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Detector

D

F

7

C

8

U

6

1 : Source and simple lens doublet (“Einzellens")

2,5,9,10 : Deflection plates

3,6,8 : Simple lenses

10

4

5

12

2

4 : Wien velocity filter

7 : Deflection quadrupole

11 : Focalisation quadrupole

12 : Deceleration plates

13 : Interaction zone

14 : Pulsed Ti:Sa laser

15 : Column of constant F

16 : MCP

17 : Phosphor screen

18 : CCD

9

1

11

13

3

j

F = 427 Vm-1

Rmax

R

Photocurrent (arbitrary unit)

OD = 0

Radius (arbitrary unit)

Photocurrent (arbitrary unit)

OD = 0.4

Radius (arbitrary unit)

Photocurrent (arbitrary unit)

e

neutral

atom

OD = 1

Radius (arbitrary unit)

hn

eA

Photoelectron energy as a function of the laser pulse energy

negative

ion

Elaser (mJ)

Photodetachment microscopy with a pulsed laser and sub-meV ponderomotive effects

Christophe Blondel, Christian Delsart, Cyril Drag & Ramón J. Peláez

Laboratoire Aimé-Cotton, Centre national de la recherche scientifique, bâtiment 505, université Paris-sud, F-91405 Orsay cedex, France

Photodetachment microscopy

Single-mode pulsed laser

Main properties

a

Dual polarization stabilized He-Ne

Single longitudinal mode

Sigmameter

Classical parameters

ion

WSU lambdameter uncertainty: +/-0.041 m-1

Tunable (250 m-1)

Highest height

Freq. doubled Q-CW

Yb:YAG 515 nm - 20 Hz

quasi-CW Ti:Sa150 µs

Short & long term stabilized(+/- 20 MHz for 100 min)

Maximum radius

L. Cabaret, Appl. Phys.B 94 (2009) 71

z0

Quantum parameters :

Frequency-doubled Nd:YAG 25 mJ @ 532 nm

Pulsed Ti:Sa

~ 10 mJ @ 848 nm

Pulse duration ≈ 25 ns

Wavelength scale

Energy ≈ 3- 10 mJ

L. Cabaret and C. Drag, Eur. Phys. J. Appl. Phys.37 (2006) 65

Detector

Number of rings

Interfringe

interval

Radial current density

l0 = 0.045mm

a = 0.35mm

e = 0.926 ± 0.002 cm-1

Principle:Y.N. Demkov et al., JETP Lett. 34 (1981) 403

Photodetachment microscopy:C. Blondel et al., Phys. Rev . Lett. 77 (1996) 3755

Photoionization microscopy:C. Nicole et al., Phys. Rev . Lett.88 (2002) 133001

Molecular photodetachment microscopy :F. Goldfarb et al., J. Chem. Phys.122 (2005) 014308

Photodetachment microscopy in a magnetic field :W. Chaibi et al., Eur., Phys. J. D 58 (2010) 29

Ponderomotive effects observed in O-

Presence of an EM field reduces the “free” electron kinetic energy by Up=q2E2/4mw2

Highlight dans Eur. Phys. J. D

Experimental set-up

Barycenter

Accumulation

18

17

16

Photodetachment images obtained on O- with attenuation by an optical density OD between 1 and 0.

15

The number of interference rings decreases when the optical density decreases, i.e. when the laser peak intensity increases. At the peak intensity, the energy shift revealed in this way would be -0.27 cm-1/mJ, but the observed effect appears attenuated by the three-dimensional integration on the whole interaction volume and the pulse duration.

14

PAMO 2010 and ECAMP X


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