Relativistic quantum dynamics in extremely strong electromagnetic fields

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Nov 16, 2013 (3 years and 10 months ago)

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Relativistic quantum dynamics in
extremely strong electromagnetic fields
Andrey Surzhykov
Physics Institute of the University of Heidelberg
and
Atomic Physics Division at GSI, Darmstadt
Work is supported by Helmholtz
association
under the project VH-NG-421
DPG Frühjahrstagung
2 March 2009
Heavy ion research: Novel developments
During the last decade, tremendous progress
has been made in the development of novel ion
storage ring and electron beam ion trap (EBIT)
facilities as well as of new position and energy
sensitive solid state detectors.
This opens up new possibilities for investigation
of simple atomic systems in extremely strong
electromagnetic fields.
hydrogen-like heavy ion
DPG Frühjahrstagung
2 March 2009
DPG Frühjahrstagung
2 March 2009
Atomic physics with highly-charged, heavy ions
During the last decade, atomic physics studies with highly-charged heavy ions
have attracted much of interest both in experiment and theory.
Heavy ions provide a unique tool for investigation ultra-strong and ultra-short
electromagnetic interactions.
()
2
/
1
1
c
v
=
γ

E ≈ 1016
V/cm
Intense Laser
“structure” studies
“collision” studies
relativistic, hyperfi
ne, QED
and PNC phenomena
Atomic structure and dynamics in strong fields
We discuss today three processes which may be utilized to study relativistic
and magnetic interaction phenomena on the structure and dynamics
of
simple atomic systems:
Negative continuum dielectronic
recombination
alternative route to study positron production is a “single-center” Dirac
problem
“Standard” dielectronic
recombination
detailed analysis of the Breit
contribution to e-e
interactions
Coulomb excitation
magnetic terms in ion-atom interactions
DPG Frühjahrstagung
2
March 2009
Pair creation in relativistic ion collisions
DPG Frühjahrstagung
2 March 2009
Electron-positron pair production in ion-
ion collisions (at moderate
energies)
has attracted much interest during last
years.
Theoretical description of such a process
requires an analysis of two-center
Dirac
problem!
target
projectile
D
. C. Ionescu
and A. Belkacem, Phys.
Scr
. T80 (1999)
128
Au79+
+ U92+
+ mc2
-
mc2
0
e+
+
mc
2
-
mc
2
0
e
+
”target” “projectile”
Pair creation in relativistic ion collisions
DPG Frühjahrstagung
2 March 2009
An alternative process for pair production
in a “single center problem”
has been
proposed recently.
In the negative continuum dielectronic
recombination a free (or quasi-free)
electron is captured by a heavy ion via the
creation if a positron-electron pair.
+ mc2
-
mc2
0
+ mc2
-
mc2
0
e+
“standard” dielectronic
recombination
negative continuum dielectronic
recom
b
i
n
ati
o
n (NCDR)
+
+


+
+

+
e
X
e
X
Z
Z
)
2
(
NCDR: Theoretical description
DPG Frühjahrstagung
2 March 2009
bound electrons
incident electron
outgoing positron (pf, mf) =
incoming electron (-pf, -mf)
Differential cross section:
With the transition amplitude:
(
)
2
2
4
2
if
f
i
f
v
d
d
τ
π
σ
p
=

()
()
(
)
f
f
i
i
m
p
m
p
f
if
f
i
i
E
E
i





Ψ
=

ψ
ψ
ω
α
τ
δ
π
,
exp
1
2
2
1
2
1
2
1
r
r
r
r
α
α
electron-electron interaction (Feynman gauge)
Electron-electron interaction operator
includes not only Coulomb term but
also magnetic interactions.
Anton Artemyev
Poster A34.21 (Th)
A. N.
Art
e
myev
et a
l
., Ph
ys
.
Re
v. A 67
(2003)
052
711
NCDR: Total cross sections
DPG Frühjahrstagung
2 March 2009
e + U92+
e + Pb82+
Tp: 1.8 GeV
... 5.5 GeV
Capture into 1s
2
st
at
e
NCDR cross sections are of order
µ
barn.
Just to compare:
The
NCDR
cross
sections
are by (about) six
orders of magnitude
smaller
than
the RR cross sections.
Calculation have been also performed
for
the
NCDR into excited states of
finally helium-like ions (up to n=4).
Capture
into excited states enhance the
total NCDR cross section by about 70 %.
A. N
.

Ar
te
mye
v
,
V. M.
Shabaev, Th
. Stö
h
lker
,
and
A.S.,
Ph
ys
. Re
v. A (ac
c
epted
)
Experimental observation of NCDR process
DPG Frühjahrstagung
2 March 2009
Despite rather small cross sections, NCDR process is likely
to be observed at the
future FAIR facility which will provide highly energetic (up to 5 GeV/u) and intense
(up to 1012
particles/pulse) heavy ion beams.
The “signature” of the process is: forward positron emission (in
lab. frame)
associated with projectiles that captured two electrons.
One may think of making NCDR process more “visible” by using gas
jet or even
solid-state targets.....
.... But! Competitive processes may results in a rather strong background!
work in progress!
A. N
.

Ar
te
mye
v
,
V. M.
Shabaev, Th
. Stö
h
lker
,
and
A.S.,
Ph
ys
. Re
v. A (ac
c
epted
)
Atomic structure and dynamics in strong fields
We discuss today three processes which may be utilized to study relativistic
and magnetic interaction phenomena on the structure and dynamics
of
simple atomic systems:
Negative continuum dielectronic
recombination
alternative route to study positron production is a “single-center” Dirac
problem
“Standard” dielectronic
recombination
detailed analysis of the Breit
contribution to e-e
interactions
Coulomb excitation
magnetic terms in ion-atom interactions
DPG Frühjahrstagung
2
March 2009
Dielectronic
recombination and Breit
interaction
DPG Frühjahrstagung
2 March 2009
Dielectronic
recombination (DR)
is a
resonant process in which a free
electron is captured into an ion under
the simultaneous excitation of bound
electron(s), and where the multiply
excited ion is stabilized afterwards by
photon emission.
Role of relativistic Breit
interaction
in DR/Auger process has been in
focus of intense studies during last
two decades.
()
(
)










+

+
=
+
=
12
2
12
2
2
1
1
12
12
2
1
12
cos
cos
1
r
r
r
r
r
V
V
V
B
C
ee
ω
ω
α
α
ω
α
α
P. Zimmerer
et
al
., Ph
ys
. Le
tt. A 148
(1990
) 45
7
M. Pindzo
l
a
et
a
l
., Ph
ys
. Re
v.
A
43 (199
1
)

570
S. Fr
itzs
che
et a
l
., Ph
ys
. Re
v.
A
44 (199
1
)

388
and man
y

othe
rs
...
Dielectronic
recombination and Breit
interaction
DPG Frühjahrstagung
2 March 2009
DR/RTE provides a tool to investigate magnetic (Breit) terms in the electron-
electron interaction.
Strong
effect was found for the resonant strengths
(total cross section).
What is the effect for differential
properties
whic
h
are more sensitive to magnetic interactions?
[
]
[
]
1
2
2
/
1
2
2
2
1
2
1
p
s
s
e
s
s

+

Angular and polarization resolved spectroscopy
DPG Frühjahrstagung
2 March 2009
[]
[
]
γ
+

0
2
2
1
2
2
1
2
2
1
s
s
p
s
s
We analyzed the angular and polarization
properties of the characteristic x-ray radiation.
Angular distribution:
Linear polarization (measured) perpendicular
to the collision direction:
)
(cos
P
2
1
)
(
2
2
θ
θ
A
W
+

2
2
2
4
2
3
)
2
/
(
A
A
P


=
=
π
θ
Alignment parameters
describe
a magnetic sublevel population
following resonant capture:

Ψ
+
Ψ
p
ε
Breit
C
P
J
V
V
A
d
d
...
~
2
0
1
0
1
2
2
2
σ
σ
σ
σ
+

=
±
±
A
M
J
= -1

M
J
= 0
M
J
= +1
Example:
J
=1 state
Breit
interaction effects in DR
We have investigated effect of Breit
interaction
on the population of excited ionic states and,
hence, on the subsequent decay radiation.
[]
[
]
γ
+

0
2
2
1
2
2
1
2
2
1
s
s
p
s
s

Ψ
+
Ψ
p
ε
Breit
C
P
J
V
V
A
d
d
...
~
2
only Coulomb
Coulomb + Breit
Breit
interaction strongly
affects emission pattern of
the characteristic radiation!
)
(cos
P
2
1
)
(
2
2
θ
θ
A
W
+

DPG Frühjahrstagung
2
March 2009
S. F
r
itzs
che
and A.S, in

prepa
r
ation
Breit
interaction effects in DR
We have investigated effect of Breit
interaction
on the population of excited ionic states and,
hence, on the subsequent decay radiation.
[]
[
]
γ
+

0
2
2
1
2
2
1
2
2
1
s
s
p
s
s

Ψ
+
Ψ
p
ε
Breit
C
P
J
V
V
A
d
d
...
~
2
... and its linear polarization!
2
2
2
4
2
3
)
2
/
(
A
A
P


=
=
π
θ
o
n
ly Co
ul
om
b
Co
ul
om
b
+ Breit
DPG Frühjahrstagung
2
March 2009
S. F
r
itzs
che
and A.S, in

prepa
r
ation
Atomic structure and dynamics in strong fields
We discuss today three processes which may be utilized to study relativistic
and magnetic interaction phenomena on the structure and dynamics
of
simple atomic systems:
Negative continuum dielectronic
recombination
alternative route to study positron production is a “single-center” Dirac
problem
“Standard” dielectronic
recombination
detailed analysis of the Breit
contribution to e-e
interactions
Coulomb excitation
magnetic terms in ion-atom interactions
DPG Frühjahrstagung
2
March 2009
Coulomb excitation of heavy ions
DPG Frühjahrstagung
2 March 2009
A number of experiments have been performed
recently to investigate Coulomb excitation of
heavy ions in collisions with low-Z atomic
targets.
Special attention has been paid to investigate
relativistic (magneic) part of the EM interaction
between target and projectile electrons.
()
β
α
γ
µ
+

=
,
0
,
0
,
1
r
Z
A
Lienard-Wiechert
potential:
Coulomb excitation of heavy ions
DPG Frühjahrstagung
2 March 2009
A role of magnetic interaction for the proper
analysis of total excitation has been outlined.
γ
+


2
2
1
2
1
1
s
p
s
s
Again, can we address a question: how
the
di
fferential properties of characteristic
radiation are affected by the relativistic
(magnetic) effects in
Coulomb excitation.
Coulomb excitation : Alignment of excited states
DPG Frühjahrstagung
2 March 2009
Alignment parameter A
2
Calculations of the alignment of the He-like ions
following Coulomb excitation have been performed
by taking full interaction
into account:
Vector-potential term gives rise to magnetic
interactions
1s
21
S
0
1s 2p
3/2
1
P
1
M
J
=0
M
J
=0
M
J
=-1 M
J
=+1
1s 2p
3/2
2
1
P
1
()
()
2
3
2
2
0
2
e
1
)
(
0
i
i
f
q
q
q
dq
q
ψ
βα
ψ
β
σ
µ
qr





M
J
= -1

M
J
= 0
M
J
= +1
M
J
= -1

M
J
= 0
M
J
= +1
0
1
0
1
2
2
2
σ
σ
σ
σ
+

=
±
±
A
A.S., U
.

Jentschu
r
a, S. F
r
itz
sche
and Th. Stöh
lke
r
,
P
RA
77 (2008
)
04272
2
Coulomb excitation : Alignment of excited states
DPG Frühjahrstagung
2 March 2009
Alignment parameter A
2
1s 2p3/2
21P1
Up to now Coulomb excitation has been
observed only at few collision energies.
New series of experiments is required to make a
“scan” over the projectile energies from 100 to
600 MeV/u.
A.S., U. Jentschura, S. Fritzsche and Th. Stöhlker,
PRA 77 (2008) 042722
)
(cos
P
2
1
)
(
2
2
θ
θ
A
W
+

Tp=217 MeV/u
Atomic structure and dynamics in strong fields
We discussed today three processes which may be utilized to study
relativistic and magnetic interaction phenomena on the structure
and
dynamics of simple atomic systems:
Negative continuum dielectronic
recombination
alternative route to study positron production is a “single-center” Dirac
problem
“Standard” dielectronic
recombination
detailed analysis of the Breit
contribution to e-e
interactions
Coulomb excitation
magnetic terms in ion-atom interactions
DPG Frühjahrstagung
2 March 2009
Many thanks to
DPG Frühjahrstagung
2 March 2009
Anton Artemyev
University of Heidelberg
Stephan Fritzsche
University of Oulu
Nikolai Kabachnik
University of Hamburg
Thomas Stöhlker
AP team
GSI, Darmstadt
Alexander Voitkiv
Benasser
Najjari
MPI-K
, Heidelberg
Ulrich Jentschura
Missouri University in Rolla
Thank you very much for your attention!
Financial support:
Helmholtz
association & GSI