interference effect in heavy ion collisions with h 2 :
DESCRIPTION
Interference effect in heavy ion collisions with H 2 : By comparing the experimental electron spectrum from atomic H. L. C. Tribedi. Deepankar Misra , U. Kadhane, Y.P. Singh Tata Institute of Fundamental Research, Colaba, Mumbai-400 005, India . Pat Richard, JRM, KSU P. Fainstein. - PowerPoint PPT PresentationTRANSCRIPT
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Interference effect in heavy ion collisions with H2:
By comparing the experimental electron spectrum from atomic H.
L. C. Tribedi.Deepankar Misra , U. Kadhane, Y.P. Singh
Tata Institute of Fundamental Research, Colaba, Mumbai-400 005, India.
Pat Richard, JRM, KSU
P. Fainstein
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• Another view
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Tata Institute, Mumbai (Bombay)
TIFR On Arabian Sea
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Introduction• Detection of low energy electrons emitted in atomic
collisions provide crucial information on the various ionization-mechanisms.
• The e-DDCS spectrum identifies different processes such as soft electrons (SE), electron capture in continuum (ECC) cusp and the binary encounter (BE).
• In addition, the e-spectra from H2, is very rich since it can provide the evidence of the interference effect.
• Since the two H-atoms in molecular hydrogen are indistinguishable, their contributions to the ionization add coherently and an interference effect might be expected.
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VOLUME 87, NUMBER 2 PHYS ICAL RE V IEW LETTERS 9 JULY 2001
Evidence for Interference Effects in Electron Emission from H2Colliding with 60 MeVu Kr34+ Ions
N. Stolterfoht et al.
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RAPID COMMUNICATIONS
PHYSICAL REVIEW A 67, 030702(R) (2003)
Interference effects in electron emission from H2 by 68-MeV’u Kr33ø impact:Dependence on the emission angle
N. Stolterfoht et al.
Expe
rimen
tal-to
-theo
retic
al ra
tio
Zeff=
1.19
for H
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Experimental Details• The electrons emitted from H2 were detected by
an hemispherical electrostatic analyzer between 1 and 1000 eV for 10-12 angles between 150 and 1500.
• We show “fully measured” (Experiment with atomic Hydrogen ) interference oscillation for relatively lower collision energies: 1-2.5 MeV/u C6+ and F9+ on H2/H.
• Also derived the oscillations using Calculated DDCS for H : 6 MeV/u C6+ + H2.
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Experimental Setup
F.C.
Slit System
IonizationGauge
Gas InletM.K.S.
HV1 HV2 Vcom
CEM HV& Signal
Turn Table
Shaft
CEMAnalyzer
Turbo
1000 l/Sec
700 l/SecDiff Stack
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Block Diagram
CFD TFA BIAS CEM
Computer
F.C.
C.I.
DAC3
DAC1
Scalar
DAC2
DAC4
HV1 HV2Electrostatic
Analyzer
Microcontroller
RS-232
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Energy Distribution.
Energy Distribution of secondary
electrons emitted from
H2 by collision with
6MeV/u. bare C ions. 1 10 100 1000
10-6
10-5
10-4
10-3
10-2
10-1
100
101
1 1 0 1 0 0 1 0 0 01 0 -7
1 0 -6
1 x 1 0 -5
1 x 1 0 -4
1 0 -3
1 0 -2
1 0 -1
1 0 0
1 0 1
= 7 5 o
DD
CS
( M
b )
E n e rg y (e V )
E xp t. C D W - E IS
=90o
DD
CS
( M
b )
Energy (eV)
Expt. CDW - EIS
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1 10 100 100010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
1 10 100 100010-5
10-4
10-3
10-2
10-1
100
101
1 10 100 100010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
1 10 100 100010-6
10-5
10-4
10-3
10-2
10-1
100
101
1 10 100 100010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
1 10 10010-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
= 45O
CDW - EIS
=60o
=75o
DD
CS
( M
b )
=90o
=110o
Energy (eV)
=135o
Energy Distribution6 MeV/u C6+ + H2
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Angular Distribution.
20 40 60 80 100 120 14010-4
10-3
10-2
10-1
100
6 MeV/u C6+ + H2
DD
CS
( M
b )
Angle ()
ev5 ev11 ev31 ev100 CDW-EIS. CDW-EIS. CDW-EIS. CDW-EIS.
Angular Distribution of
secondary electrons
emitted from H2
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0 1 2 3 4
1
2
0 1 2 3 40.0
0.5
1.0
1.5
2.0
1 10 100
1x10-5
1x10-4
10-3
10-2
10-1
100
0 1 2 3 4 5 60.20.40.60.81.01.21.4
1 10 100 1000
0 2 4 6 8 10 12 14
0.5
1.0
1.5
2.0 1 10 10010-5
10-4
10-3
10-2
10-1
100
101
(f)
AI peak
1050
D2
D1
(g)
Velocity (a.u.)
1500
(a)
= 450
DD
CS
(Mb)
Energy (eV)
(d)
= 450
DD
CS
Rat
io (R
)
(b)
=75o
Energy (eV)
(e)
=75o
(c)
1050
Energy (eV)
Interference at different angles.
6 MeV/uC6+ + H2
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6 MeV/u C6+ + H2.:45o,75o.
0 2 4 6 8 10 12 14
0.4
0.6
0.8
1.0
1.2
1.4
0 1 2 3 4 5 6
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
6MeV/u C6+ + H
2
Expt. CDW-EIS
(b)
ZT=1.19
750
Velocity (a.u.)
6MeV/u C6+ + H2
Expt. CDW-EIS
(a)
ZT=1.19
450
DD
CS
Rat
io (R
)
Dependence of the phase and
amplitude of the oscillation on
different choices of effective target
atomic number (ZT) in the calculation of
DDCS for H.
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Interference in backward angles.
0 1 2 3 40.5
1.0
1.5
1 10 10010-5
10-4
10-3
10-2
10-1
100
Expt. CDW-EIS
1500 (b)
RN
Velocity ( a.u. )
6MeV/u C6+ + H
2
Expt. CDW-EIS
(a)1500
DD
CS
(Mb)
Energy (eV)
Frequency of oscillation is higher in backward angles
compared to forward angles, as
predicted by theoretical model.
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0 2 4 6 8 10 12 14 16 18
0
200
400
600
800
Dissociation Fractionusing 9 eV proton method1 MeV/u C6++H/H
2
=45o
Df=88%
RF ON RF OFF
Pro
ton
Yie
ld (a
rb. u
nits
)
Proton Energy (eV)
Expt a
t JRML,
KSU
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“Fully Measured” interference structure.
0.5
1.0
1.5
2.0
1 10
0.5
1.0
1.5
45o
(a)1MeV/u C6+ + H
2/ H
60o
CDW-EIS
Velocity (a.u.)
(b)
DD
CS
Rat
io (R
)
Fully Measured DDCS Ratio for
H2 & H.
Dependence on projectile atomic
number is investigated.
Accepted in Phys. Rev. Lett. 2004.
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Comparison between different methods.
0.5
1.0
1.5
1 100.0
0.5
1.0
1.5
2.0
2.5
1 10 100 100010-6
1x10-51x10-4
10-310-210-1100101
6 8 10 120.5
1.0
1.5
Expt. CDW-EIS
1.5 MeV/uF9+ + H
2 / H
(a)
45o
Expt. CDW-EIS
R
(b)
60o
DD
CS
Rat
io (R
)
Atomic H
BE
Expt. CDW-EISD
DC
S (M
b)
E(eV)
Velocity ( a.u. )
45o
Experimentally measured Cross
section for H was used to derive the interference
oscillations and a comparison was made.
(using theoretical values for atomic H)
Fully Measured DDCS Ratio for H2 &
H.
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Absolute DDCS for H and ratio
1 10 100 1000
1
2
310-4
10-3
10-2
10-1
100
1 10 10010-4
10-3
10-2
10-1
100
101
(c)Ratio 60O
DD
CS
( H2 )
/ D
DC
S(H
)
Energy (eV)
B.E.
(b)
DD
CS
(Mb/
eV-s
r)
60O
CDW-EIS FBA
(a)
C6+ + H
30O
Tribedi, R
ichard
et al.
J.Phys.B
(letts.
) 31, L369
1998
The o
scilla
tion i
n the
ratio
was ob
serv
ed b
y us e
ven
earlie
r
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Conclusions• Interference effect is not only a phenomena of high energy
collisions. It is important at relatively low collision energies also.
• The dependence of the oscillations on the projectile atomic number is very weak.
• First study of “fully measured” ratios giving a direct evidence of the interference effect.
• Present method is free from:i) the normalization procedure.ii) choice of theoretical parameters like ZT
iii) systematic experimental errors.
[D. M
isra, U
K, YPS, L
CT
Richard, P
F (PRL 2004, in
press)]
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References
[1] N. Stolterfoht et al., Phys. Rev. Lett., 87 023201 (2001).
[2] M.E. Gallasi et al., Phys. Rev A 66, 052705 (2002).
[3] L. Nagy et al., J. Phys. B 35, L453 (2002).
[4] Deepankar Misra et al., ( Accepted in Phys. Rev. Lett.,)
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6 MeV/u C6+ + H2: 300
0 2 4 6 8 100.0
0.5
1.0
1.5
2.0 Experiment. Model Fitting.
30o
DD
CS
Rat
io
Velocity ( a.u. )
Frequency doubling and Double Scattering.
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Single Scattering Double Scattering
1
2
1
2
1
2
(T1+T2)
(T2G0T1) (T1G0T2)
T = (T1+T2) + (T2G0T1 + T1G0T2) + (T2G0T1G0T2 + T1G0T2G0T1) + …T1 = V1 + V1G0V1 +V1G0V1G0V1+…T2 = V2 + V2G0V2 +V2G0V2G0V2+…
k0k0
k0
kk
kk’k’’
k0 = q - k
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6 MeV/u C6+ + H2: 600
0 1 2 3 4 5 6 7 8 9
0.50
0.75
1.00
1.25
DD
CS
Rat
io
600
Velocity ( a.u.)
Experiment. Model Fitting.
A double scattering model is
considered. The electrons emitted
from one center get scattered by the
other center, giving rise to a doubling
of the frequency in the interference
oscillations.
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Experimental TechniqueElectron spectroscopy:
****C60 vapour source (450-500o C)
*** Hemispherical Electron Analyzer.
*** Preaccleration voltage = +5V
*** metal shielding used to reduce mag. Field (below 5 mG)
*** Gas pressure kept low : 0.1 mTorr
*** electrons between 1 eV to 6 keV
****12 angles between 200 – 1600 degree
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Lokesh C Tribedi
Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
Students: U.Kadhane D. Misra Y.P.Singh, Aditya Kelkar : Post doc: Ajaykumar
Sc. And Tech. Staff : K.V.Thulasiram W. Fernandez And Pelletron Accelerator Staff
X- Ray and electron emission in heavy ion collisions with
fullerenes and solids: The collective response
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X-ray set up with Pelletron
14 M
V Pelletr
on Acce
lerator And a LINAC booster coming up
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Projectile
Targetn=1
n=2
n=3
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Typical Lyman x-ray spectra
1.5 2.0 2.5 3.0 3.5 4.00
100
200
300
400
2.4 2.5 2.6 2.7 2.80
200
400
2.0 2.5 3.0 3.50
100
200
300
110 MeV S16+ on C60(H)
(N)Ly
Ly
Ly
Cou
nts
Energy (keV)Ly
(H)
(N)
C60
N2
C60
Cou
nts
(N)
(H)
(Background)
Energy (keV)
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0 5 10 15 20 25 30 35 40
0.15
0.20
0.25
0.3
0.4
0.5
0.6
120 MeV S16+ (b)
I()
/ I()
Target Atomic No.
I(
) / I() Gas targets C
60(a)
Lyman Ratios for gases and C60
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The ratio of Ly/ Lyfor solid and gas
GANIL Expt., V=36 a.u.Bare Kr ions on C,Al, Cu and N2 & ArRozet et al.
The Lyman ratio is 20-25%Lower for solids w.r.t gases
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Lyintensity for solid and gasEffect of wake field and Stark mixing
Parameters: d, p, s, p
Stark mixing of 2so & 2po in strong wake field (109 V/cm) in a very small time scale 5.10-17sec.
Population changes in 2s and 2p
Metastable 2s
Small 2s-1s M1 transition (3%)Ly enhancement
s 2so, 2po=3.8 eV for S
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Wake phenomena and e-density fluctuations: Echenique, Ritchie, Brandt; and Burgdoerfer
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Comparison of the ratio i.e. C60 / N2
Difference ~ 15%\i() (for capture)• Model predicts ~ 10%• Other mechanisms: Post
collisional effect!• Effect of Giant dipole polarization
and Stark mixing!
110 120 130 1400.40.50.60.70.80.91.01.11.2
CDW+"Stark-Mixing"
CDW (ion-atom)
16+
13+
Rat
io (R
cg)
Energy (MeV)
Kadhane et al PRL 90
093401 (2
003)
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A comparative study
ions Z/ V Quantity Solid st. effect d (s) • Kr36+ 1.0 Ly ratio 20-25% ~ 10-15
• S16+ 1.3 Ly-ratio 15% ~5.10-17
• Cl17+ 1.4 Ly ratio 20 % ~5.10-17
• Si/S/Cl 1.1-1.5 REC 40-50%• C/O/F <0.5-1 REC No measurable effect
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Ly ratio in collisions with Cl17+
1 100.2
0.4
0.6
0.8
Dec 2002 run
120 MeV Cl17+
ZT
(Ly
+ L
y )
/ Ly
13 14 15 16 170.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Rat
io(C
60 /
CH
4)
Charge State
D
C60
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E-DDCS spectrum of C60
1 10 100 100010-4
10-3
10-2
10-1
100
101
102
103
C60
N2
BE
KLL Auger
45 MeV C6+
= 600 N2
C60
R
el D
DC
S
Energy (eV)
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Future?• A new ion source, 14.5 GHz ECR source, (obtained
from Pantechnik, France) will be installed dedicated mainly for atomic collisions in the low energy region.
• It will be coupled with a 300 kV accelerator.• High resolution x-ray, electron spec, ToF• Noble gas cluster/ fullerenes• May be coupled with a laser• ………..• ………..
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0 5 10 15 200
100020003000400050006000700080009000
10000
evapnFragmentation
C60
4+
C60
3+Vd = 1800V
Cou
nts
20 30 40 50 60 700
10000
20000
30000
40000
50000
40 50 60
100
1000
10000
100000
C60
2+
C60
1+
Vd = 1800V
Cou
nts
M/q in terms of 12 a.m.u. (No. of C atoms)
36 38 42 44 46 4850 52
54
5856
C60
1+
The Fragmentation Recoil Ion Spectra of C60
Evaporation
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Electron density distribution along trajectory in C60
-10 -5 0 5 100
2
4
6
8
10 Impact parameter 9.9 a.u. (<n>=1.366e28 m-3) Impact parameter 9 a.u.(<n>=4.41e28 m-3) Impact parameter 6 a.u.(<n>=3.41e29 m-3) Impact parameter 2 a.u.(<n>=3.086e29 m-3)
Ele
ctro
n D
ensi
ty (i
n a.
u.)
Rparallel
(in a.u.)
Hadjar, Hoekstra, Morgenstern, Schlatholter, PRA 63, 033201 (2001)
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1 10
1
10
100
1000
10000
(x 1
0-1
9 c
m2 )
CDW Gas Targets C
60
tot
Target Atomic No. ZT
Total Ly x-ray cross section due to capture
*The CDW over estimates the cross sectionsat v=13
*CDW reproduces the dataat v=36 a.u.
*Higher order terms play a role giving saturation
*The data for C60 falls on “gas-line”
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We are at work!! Electron spectroscopy set up
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TOFMS
FUTURE PLAN
Electron Spec.
Charge-state
analysis
X-ray
Deepankr
YeshpalUmesh
Umesh