cold collisions in the presence of...
TRANSCRIPT
united nationseducational, scientific
and culturalorganization
national atomicenergy agency
the2international centre for theoretical physics
SMR 1302- 4
WINTER SCHOOL ON LASER SPECTROSCOPY AND APPLICATIONS
19 February - 2 March 2001
COLD COLLISIONS IN THE PRESENCE OF LIGHT
Vanderlei S. BAGNATOUniv. de Sao Paulo, IFSC - Center for Optical Science & Photonics
SP-13560-970 Sao CarlosBrazil
These are preliminary lecture notes, intended only for distribution to participants.
strada costiera, I I - 34OI4trieste italy - tel.+39 04022401 I I fax +39 040224163 - [email protected] - www.ictp.trieste.it
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Temperature
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IK
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\Chemistry
ConventionalAtomic Beams
\Liquid He
Velocity SelectedAtomic Beams
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Dopplef CoolingOptical Traps
\Optical Molasses
\Magnetic Traps
\Evaporation
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nW/cm2 / /y*
nW/cm2 7 / / /
• typ.n //SZ&'trap
A0F1 • ! •
I 2
TIME (»ec)
UNIFORM DENSITY DIST.' INTRA-TRAP COLLISIONS
6AUSSIAN DENSITY DIST.INTRA-TRAP COLLISIONS
GAUSSIAN DENSITY DIST.BACKGROUND GAS COLLISIONS
~1 1 1 1 1 1 —20 40 60 80 100 120
TIME (sec)
o t k <a|
Cx, A ,
-QoadvVj
Load
Nc
3q
C V)CX Y)
FIG. 26. Fluorescence-time spectrum. The abrupt drop at theinitial moment is due to a change in light intensity withoutvariation in the number of trapped atoms. From Santos et al.(1996).
x]
ioqj iJ
_LT
TIyf''
0 20 40 60 80 100 120 140 160
Intensity (mW/cm2)
SeuemL C 3H*\ -̂e
0LOCJO
/Kv
v
H-CC2
HrO
•x-
JT-lc
X1
ie> a
cevr)i ela ssicoL
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Once 11\ b
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4 = U5^TT^d^'B
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coLII10
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° 57 4
2 3^ 2
10
_
—
—
—
*~ Ja— ^ y
—7 T
0
V,«.2O,r
nf H•!# !t 1
100
INTENSITY
WVIII
m $ec""'
r - 1 " ^TI
• i i i200 300
ImWcm"2 )
2.3
1.0
i
5- 5-l i i i i i i • i i 1
- 1 0 0 0 - 6 0 0 - 6 0 0 - 4 0 0 -200
FIG. 28. Measurement of the trap loss rate constant as a func-tion of MOT light intensity. The wider range of light intensityreveals an increase in /3 with MOT intensity. Dotted, full, anddot-dash curves are theory calculations using the optical-Blochequation method of Band and Julienne (1992) with differentassumptions about the maximum escape velocity of the MOT.The curve VtK= V{1) results from a simple model in which theescape velocity is a function of the MOT intensity. Data arefrom Marcassa el al. (1993).
1.3
o.e
0.3
0 .0
(b» P«/2 H
- i . i , , , , , I ,
-1000 -B00 - 6 0 0 - 4 0 0 -200 0Wp-w, (MHz)
FIG. 29. Trap-loss spectrum in a Na MOT for cat.il>sis laserdetuned to the red from both atomic line-structure .-isympintes.From Marriicco ot „ / MOO^
1 0 " 4
i.o-'N
20
It(mW/cmz)
FIG. 32. Trap-loss spectrum for two isotopes of rubidium.Right-hand branch shows trap loss due FCC and RE. Left-hand branch shows trap loss due to HCC. From Wallace el al.(1992).
1 O It
Os A
10
10 3 € 9 12
INTENSITY lmW/cm2)
. 30. Trap-loss rate constant ft as a function of MOT in-ity for Cs collisions: comparison of experiment with GPry. from Sesko et al. (1989).
-1200 - 9 0 0 - 6 0 0 - 3 0 0 0
DETUNING OF CATALYST LASER (MHz)
.„-»
io-n
"I10"
10"
10,-13
€yc\\e
- 3
0 30 60 90 120 0 30 60 90 120
10"
iri
• I
A--3.5T
i i i i
10",-10
30 60 90 12010"
" I
30 60 90 120INTENSITY (mW/cm2)
FIG. 40. Trap-loss rate constant /3 for four different detuningsand a range of intensities in the Rice group's Li MOT. Thevertical lines in each plot denote / r the calculated critical in-tensity required to recapture an atom released in the shallow-est direction. From Ritchie et al. (1995).
JT-23
* X-t
*
" ^ 4Jr5 60 80 100 120 140 160 180
INTENSITY lmW/cm z )
'Bcas/LM
r f»a)
j Diode Laser(repumper)
Krypton ion laser
Dichroic mirror
to,
1—/•'
— r
= 4
= 3
= 3
= ?
Continuum
RC. ., ~
• V | / 2 -
Kryplonw,, (X =
135 MHz
160MII7.
ion laser640 nm)F' = 3
F' ~ 2[JOH mn)
F = .1
F = 2
Fig. 2. Cw dcfccljon scheme. I he pniduccd 5l\n alumsgcneralcd from FSC collisions arc cscitrd lo Wj / j sl;ilc bya first photon from a dye laser (X = 607 nm) and then ioni7t-dby a second photon (A. = 640 nm) pmvcnicnl of a Kryptonion laser.
pjg. l. Experimental setup. Rubidium is trapped in a MOTsing a Ti:sapphire laser while a dye laser is tuned to the
_p _>. 8S1/2 transition and the krypton laser ionizes atomsoUtof the 8Sj/2 state. A channeltron particle multiplier detectsthe ions.
(Joser.
0\CH\S
OY).
0 500 1000
Laser Frequency (MHz)
\N e v i
i s
v uJ.P. Shaffer et a/.-. Cs radiative escape and fine structure changing collisio
100 ISO 200
INTENSITY [ mW cm'2 ]
Fig. 6. Th« ratio 0FS/0HF; for a detunin<; of A - -\AF. The scatter in tho plot givevalue. The dit.i points wor.; fit to A constant to establish lh.U 0Fs/pns = 0.58 T 0.03.
Jo A
3. u
nit
s)
kJ
1.4
1.2
1.0
0.8
0.6
0 .
0.2
0 0
-
* i
_ - —
• • • • I . I
35 40 45
Intensity (m\V/cmJ)
60.0-
50.0-
40.0-
30.0-
20.0-
10.0-
0.0-
/ •
/ T"'
• // 1
-1200 1000 -BOO -600 -400 -200 0
Catalysis laser detuning (MHz)
Fig. 3 . Additional trap loss rate due to FSC introduced by thecatalysis laser, 5pSC , as a function of catalysis laser detuning,operating below the transition 5S|/2(i'n = 3) —• 5P3/2(i r ' = 4);in the frequency range of -1200 MHz < Ac < - 5 0 MHz. Thefull line represents the theoretical prediction.
Mot oV Cr
iU 4:ro p
~3^«^) \
Exciled Stale Fraction0.0-1 n.on o.i? 01
1 2 3 4
MOT Laser Intensity I (mW/mm1)
i s ooct
"tTGp2J
0 50 60 70 80 90
3T-2S
20 . 40 60 80 100 120 140 160
.|fto.a
Intensity (mW/cm2)
u e crt> <
9
CVKcJ
Tra pV3 u/ fffcp
\je\octly CVe)
\M o^.
IT-
77
our arcupJ
\
10 15 20 2 25
Intensity (mW/cm)
^ How
>0
1
**
l
**> i
4ooelues-
-tfoppin^ ©omoll
4 o
^ U/YI. Bonn - / ^ f •]
J2I- OorJT-33
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coil/
RENEE C. NHSNIDAL AND TIIAD O. WALKKR PHYSICAL REVIEW A 62 O3O7Ol(R)
-111-
I t ) .
5 10liilinsity hnW
FIG. I. Loss rales due to ullmcold collisions as a function oftotal trap laser intensity with a deluning of A = - 1 l \ The circlesand squares indicate data taken with a magnetic-field gradient of 10and 18 G/cm, respectively. The solid lines have been included toguide the eye.
intensity (mW/cniJ)
FIG. 2. Loss rales as a function of total trap laser intensity forlarger laser detuning*, l i te -f's and circles indicate data tqken atA ~ - 1 . 5 f and - 2 ! ' , rcspcdivrly.
tvj
op
as
4 or
40 80'
Intensity (mW/cm3)
ao.
d o.-wpi
R(a0)
JT-i
u) fib I d
1.0
0.8
0.2
0.0
R («„)
"3e
T>fonumced
•50 mW/cm
•20 mW/cm2
• 5 mW/cm
1 mW/cm2
0.22 mW/cm2
0.08 mW/cm2
0.03 mW/cm'
6000
ft-
Ve
2,0x10*
« 1,5x10"
L0X105
5,0x104
0,0
R(a0)
ITo /not
50 mW/cm
20 mW/cm2
5 mW/cm2
1 mW/cm2
0.22 mW/cm2
0.08 mW/cm
0.03 mW/cm2
4000 6000
u j
i v\ j
al beloauror (5
c
0 10 20 30 40 50 60 70
Intensity (mW/cm2) *
can pi cute// or?<&7 /m<rf
-H
c
•903
T-31
Fig.1: G.D. Telles et s/., Alternative Interpretation for theMagneto Optical Trap Losses at Low Light Intensil
V)
c
c5
1 -
10 20 30 40 50 60Intensity (mW/cm )
i 1 » i •> i
0.1 10
Intensity; (mW/cm )
O
to
f
J
SpeciesLi
NaK
Rb
Cs
-3.5
-1-7
-1
-1
Icxp(mW/cm2)28
580
3
4
inKxKmW/cm2)25
7.981
2.5
1.4
ReferenceN.W.M. Rilchie e( aJ PRA 51, R890
(95)S.R. Muniz et al, PRA 55, 4407 (97)L.G. Marcassa et al, accepted PRA
(00)CD. Wallace et al, PRL 69, 897
(92)Seskoetal, PRL 63, 961(89)
.0,0 0,2 0, 6
intensity (mW/cm )
4 -
~ 3 -
CO. 2 -
1 -
0,8
dB/dx = 10 G/cm;A = -2rFFT smooth: 4ptsA = - i ,5rFFT smooth: 4pts
7
Intensity (mW/cm )
c l<CJ
Svs+sre^i s
5.63 .6 3 .1
( oL ftB)
- R .
Qvccj
V
c/)eoses : *-^<^ ^ctn'ies Civideos
l f
Sodium loss rate (10"" cmVs) 8.ib
Iri>c
7t> 3c
P
ID
0c
1
Trap loss rates (ft? cm3/s)
c
12K
C L
CL
Ci
"3
CPCD
q-Zf.
.0
Trap loss rates (10~12cm3/s)
CD
•r
08
Doubl
V(R)
K(4P3;2)-Rb(5P3/2)
(b)
K(4S,,2)-Rb(5P3/2)
K(4S1/2)-^Rb(5S1/2)
esc Internuclear separation, R
i ^O
3.0
0.0K-Rb ( x 1 0 )
70 80 90 100 110
Potassium trap laser intensity (mW/cm )
Heteronuclear trap loss rate, p' (10~12 cmVs) HTrap loss rates, p/p1 (10" cm /s)
3=
o
3
3-3
f9*
to
P(cm3/sec)
CD ^
IS JSCD £
$
MS S c
- r50
— A— p expeiimonlal— |) Modulo GP: Rb/Rb*
—T—1»' experimental— \Y Modelo GP: Rb/Cs"
T100 150 200
Intensidade (mW/cin1)
250
50 60 70
Inten9idade (mW/cm2)
100 110
1 -
• - |» oxporlmental
|l Modelo GP: Hb/Ub"• A— p" eKpeiliTienlnl
- — H 1 Modelo GP.Rb/Cn'
.1- 1 1 • 1 • 1 « 1 • 1 • 1 ' 10 50 100 150 200 250 300 350
Intenaldade (mW/cm1)
50 60 70 80 90 100 110
Intensidade (mW/cm3)
13. 1 0 -
(D4-*
CD
</)
O
CL
£is"o
100
Probe laser detuning (MHz)
"Vo
TELLES, G.D.
/vvo
U(R)
10-
1 -
0.1 -
Sodium
• I* I
trap laser iniensuy.
« 140mW/cm2
= 70 mW/cm2
= 40 mW/cm2
1000
Probe laser detuning (MHz)
Theoretical modef
1E-12-
1E-13-
1E-14-
Re
i!c1'c1'c
Internuclear
= 40 mw/cm2
= 70 mw/cm2
= 140 mw/cm2
separation, RDouble excited <3P model
—i 1 1—i—i—i—i—
|A|, detuning (MHz)
Sod
y- Los,. fKy*. J i , IO6-2C
+ K ^ T f t . A, R2S-43
^v?T. ?
?kvs.!W, A
C
S.-\e\\es