h 0v

Detector

Fion

z0

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 with a pulsed laser and sub-meV

ponderomotive effects

Experimental set-up

qFa

0max2azR

23

032

aN

Interfringeinterval

a

z

NR

i3

00max 3

a

zRAiRj

0

2

0

2

41)(

Single-mode pulsed laser

Ponderomotive effects observed in O-

7

6

5 4

3

2

1

8

9

10

11

12

13

 1 : Source and simple lens doublet (“Einzellens") 2,5,9,10 : Deflection plates3,6,8 : Simple lenses

4 : Wien velocity filter7 : Deflection quadrupole 11 : Focalisation quadrupole 12 : Deceleration plates13 : Interaction zone

C

D

F

U

Freq. doubled Q-CWYb:YAG 515 nm - 20 Hz

quasi-CW Ti:Sa

150 µs

Dual polarization

stabilized He-Ne

Sigmameter

WSU lambdameter uncertainty: +/-0.041 m-1

Frequency-doubled Nd:YAG 25 mJ @ 532 nm

Pulsed Ti:Sa~ 10 mJ @ 848 nm

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

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

Quantum parameters :

Wavelength scale

Number of rings

Classical parameters

Radial current density

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

Highest height

Maximum radius

32

0 2mqF

14

15

14 : Pulsed Ti:Sa laser15 : Column of constant F16 : MCP17 : Phosphor screen18 : CCD

negative

ion

neutral atom

h

eA

18

16

17

Accumulation Barycenter

Photodetachment microscopy

2

'

2

1

21

U

F

C

DhA

Single longitudinal mode

Short & long term stabilized

(+/- 20 MHz for 100 min)

Pulse duration ≈ 25 ns

Energy ≈ 3- 10 mJ

Main properties

PAMO 2010 and ECAMP X

Radius (arbitrary unit)

Radius (arbitrary unit)

Radius (arbitrary unit)

Photo

curr

ent

(arb

itra

ry

unit

)Photo

curr

ent

(arb

itra

ry

unit

)Photo

curr

ent

(arb

itra

ry

unit

)

0

200

400

600

800

1000

1200

0 10 20 30 40 50

EXP

FIT

OD = 0

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40 50

EXP

FIT

OD = 0.4

0

20

40

60

80

100

120

0 10 20 30 40 50

EXP

FIT

OD = 1

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.

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

a

R

F = 427 Vm-

1

Rmax

j

0 = 0.045 ma = 0.35 m

= 0.926 ± 0.002 cm-1

Tunable (250 m-

1)

2-Oct-2009

y = -0.0255x + 0.5601

R 2 = 0.973

0.42

0.45

0.48

0.51

0.54

0.57

0.60

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Plaser (mJ)

En

erg

y (c

m-1

)

Elaser (mJ)

Photoelectron energy as a function of the laser pulse energy

Presence of an EM field reduces the “free” electron kinetic energy by Up=q2E2/4m2