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18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
1
• Molecular structure• Two-center continuum
wavefunction for the ejected electron
• Not oriented target nor particular rovibrational initial state in experiments
• Vibrational nor Rotational states resolved
Introduction
Ionization of molecules compared to atoms
Theory Experiment
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
2
• DWVA (Zurales et al, 1988)• DWO (Monzani et al, 1999)• Influence of vibrational states, electronic vertical
transitions (Weck et al, 2000)
• e+/H2+ (Fojón et al, 1996)• Effective Center Models for ion impact (Rivarola et al,
1991-2002)
Theoretical work on H2 TDCS
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
3
• Absolute Triple Differential Cross Sections (TDCS) at very high impact energy in coplanar asymmetric geometry (Chérid et al, 1989)
• Relative TDCS at high impact energy (Jung et al, 1975 in coplanar asymmetric geometry
Experimental work on H2 (TDCS)
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
4
1 22 22g ge H e H
• Modelization– Electronic vertical transitions – Fixed molecular orientation during the collision– Neglect of exchange effects
The (e,2e) process of interest is
-Intermediate and high impact energies
-Asymmetric coplanar geometries
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
5
Cross Sections
• Fivefold differential cross section for coplanar asymmetric geometries
– Averaging over all molecular orientations, triple differential cross sections are obtained
5
24(5)02 ( )ee s
fie s s i
k kdt
d d d dE k
3
2430
12 ( )
4ee sfi
e s s i
k kdd t
d d dE k
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
6
T-Matrix Amplitude• The prior version of the T-matrix element reads
1 2
1 1 A Bi
P P A B
Z ZV
r r R R
1 2 1 2( ) 2 ( , , ; ) ( , , ; )efi f i it R r r V R r r
.
1 2 1 23/ 2( , , ; ) ( , ; )2
iik R
i i
eR r r r r
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
7
Initial bound wavefunctions
1 2( , ; ) 1 2i ir r N
1 2 2 1jA jB jA jBr r r rj e e e e Berencz Wavefunction
* * * *1 2 1 2
1 2( , ; ) A B B Br r r ri HLr r N e e e e
Heitler-London by Wang
0 1 2 00.002712 0.0711 1.1202 1.4354N
*01.166 1.406 . .a u
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
8
Final wavefunction
2 22 0( ; ) A Br r
f fr N e e
Final Bound wavefunction
01.3918 1.406 . . ( )a u vertical transitions
.
1 2 13/ 2( , , ; ) ( ; )2
sik R
f f C
eR r r r r
C r Continuum wavefunction TEC, TCC, BBK
approximations
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
9
Two Effective Center (TEC) Model
ks
ke
HH
ee
e
• Ionization near nucleus• Complete screening by passive electron• One continuum
r1
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
10
TEC final wavefunction
13/ 2 .
1 1 1, , 2 , ,eik rC e C j e e j jk r k r e C k r Z
*1exp( )jr
C j is chosen
appears in the t-matrix element
with j a or b
If
Weck, Fojón, Hanssen, Joulakian, and Rivarola, PRA 63 (2001) 042709
/ 21 1, , 1 / / ;1; ( . )z kC k r Z e iZ k F iZ k i kr k r
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
11
Two-Center Continuum (TCC) Model
ks
ke
HH
e
e
• H2+ targets
• Two-continuum wave function
Joulakian, Hanssen, Motassim and Rivarola PRA 54 (1996) 1473 for H2+
r1
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
12
TCC wavefunction for H2
13/ 2 .
1 1 1, 2 , , , ,eik rC e e A sc e B sck r e C k r Z C k r Z
/ 21 1, , 1 / / ;1; ( . )z kC k r Z e iZ k F iZ k i kr k r
TCC for H2 molecules
2 1scZ Asymptotic Charge 1
Weck, Fojón, Hanssen, Joulakian, and Rivarola, PRA 63 (2001) 042709
Weck, Fojón, Joulakian, Stia, Hanssen and Rivarola, PRA 66 (2002) in press
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
13
• Boundary conditions satisfied
• Passive electron included
• Only one continuum: easy to handle
• Boundary conditions not satisfied (correction 2Zsc=1)
• Passive electron plays no role (correction 2Zsc=1)
• Two continua
TEC vs. TCC
TEC TCC
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
14
0 50 100 150 200 250 300 3500
1
2
3
4 Exp. from Chérid et al (1989) CWLA from Zurales et al (1988) TCC C-TCC TEC
s= 1 deg
3DC
S (
a.u.
)
e (deg)
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
15
• TEC treatment
• BBK correlated continuum wavefunction in the final channel
Molecular BBK Model
ks
ke
HH
e
e
e
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
16
13/ 2 .
1 1 1 1, 2 , , , , , ,eik rC e e j e s j s P P ePk r e C k r C k R C k r
ee
Z
k
ss
Z
k
1
1
2ePPk
Molecular BBK Final Continuum Wf.
17
Direct and Indirect terms
ks
ke
HH
e
e
e
, ,, ( )
, ,e dir indfi j l l j
j l j l
t t t j l a b
* *2 11 2 2. .
, 1 11
1 1, , j je l lr rik r r rdir iK R
j l C j j pp j
t e r R r e e e e er R
r1pR1
Direct Term
18
Direct and Indirect terms
ks
ke
HH
e
e
e
, ,, ( )
, ,e dir indfi j l l j
j l j l
t t t j l a b
* *2 11 2 2. .
, 1 12
1 1, , j je l lr rik r r rind iK R
j l C j j pp l
t e r R r e e e e er R
r2p
R2Indirect Term
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
19
MBBK Cross Sections• Neglecting indirect terms and averaging over
all molecular orientations
ek K
3 2253 *
0
0
4 2 , ; ,
sin( )1
e se
e s e i
k kdN I K k
d d dE k
i sK k k
20
210 240 270 300 3300
1
290 180 270
1
2
390 180 270
0
1
2
3
4
(c) s= 3°
Ejection angle e (deg)
(b) s= 1.5°
TD
CS
(a.u
.)
Ei= 4087 eV
Ee= 20 eV (a)
s= 1°
MBBK TEC Chérid M et al (1989) 2 x BBK
21
0.00
0.09
0.18
0.270.00
0.09
0.18
0.27
210 240 270 300 3300.00
0.09
0.18
(b) s=8.9°
Ejection angle e (deg)
TDCS
(a.u
.)
(a) s=8.2°E
i=4168eV
Ee=100eV
MBBK TEC Chérid et al (1989) 2x BBK (H)
(c) s=9.6°
22
0 90 180 270 3600
3
6
0
4
8
12
16
20
(b) s=8°
T
DC
S (
a.u
.)
Ejection angle e (deg)
(a) s=4°E
i=250eV
Ee=4.5eV
MBBK TEC Jung et al (1975) 2xBBK(H) DWVA
230 90 180 270 360
0
1
2
3
0
2
4
6
(c) s=12°
Ejection angle e (deg)
MBBK TEC Jung et al (1975) Monzani et al (1999) 2 x BBK (H) (b)
s=8°
Ei=250eV
Ee=9eV
TD
CS
(a
.u.)
0
3
6
9
12(a)
s=4°
240 90 180 270 360
0
2
4
0
3
6
9
12E
i= 100 eV
Ee= 4.5 eV
(b) s=15°
Ejection angle e (deg)
(a) s=7°
TD
CS
(a
.u.)
MBBK TEC Jung et al (1975) 2 x BBK (H)
18 July 2002, Metz (France)
Omar FOJON (CONICET-UNR) Argentina
25
• MBBK: Good agreement between experiments at intermediate and high impact energy
• TEC and TCC: describe well experiments at high impact energy
• Inclusion of e-e repulsion crucial to describe the binary and recoil peak region
• Extension of TEC treatment to other diatomic molecules such as N2
Conclusions and Perspectives