1
Collisional Orientation Transfer
Facilitated Polarization Spectroscopy
Jianmei Bai, E. H. Ahmed, B. Beser, Yafei Guan, and A. M. Lyyra
Temple University
S. Ashman, C. M. Wolfe, and J. Huennekens
Lehigh University
Funded by NSF PHY 0555608, PHY 0855502, PHY 0652938
and PHY 0968898.
2
Motivation
• The A~b mixed states of Rb2 and Cs2 are important in the creation of ground state ultracold
molecules.
• Missing data in the gap region is a problem for global deperturbation analysis of the A~b complex.
• We use polarization spectroscopy to cover the gap region.
Theoretical potential curves by Prof. S.Magnier
28000
3 
1 g
3
2 g
1
3 g
1 +
6 g
3 +
3  g 4 g
24000
3
Gap in the previous rotational energy
level data of Cs2 A~b states
6p6p
6s6d
6s7p
13000
6s7s
12500
1 +
5 g
LAC
Tsinghua
Innsbruck
3 +
3 g
20000
12000
4 g
16000
6s6p
1 +
A u
12000
Cs2
3
b u
8000
3 +
a u
4000
E-0.0091J(J+1)
-1
E (cm )
1 +
11500
11000
10500
10000
6s6s
9500
1 +
X g
0
2
4
6
8
0
10
12
Å
14
16
18
20
22
20000
40000
J(J+1)
60000
80000
3
Anisotropic Magnetic Sublevel Population
Created by the Pump Laser
M=-1
0
+1
(a) Level scheme for a P
transition J=2
J=1
J=1
∆M=+1
The magnetic sublevel
populations become
anisotropic
M=-2
(b) Linearly polarized
probe beam and circularly
polarized pump beam
-1
(a)
0
+1
J=2
+2
Molecular Sample
Pump Wave
Probe Wave
(b)
4
Change of the Polarization Direction
1
E  E0 (x  iy )e it
2
1
E  E0 (x  iy )e it
2



 


 

1
E  E0 (x  iy ) exp i (b   n   t ) exp  (      )
2
1

E  E0 (x  iy ) exp i (b   n   t ) exp  (      )
2

2 d
b 
Re[ n ]
c

L
n 
Re[ nv ]
c

2 d
 
Im[ n ]
c
L

 
Im[ nv ]
c

5
Profile of the Polarization Signal
background
I  I 0e
 2 (   )
Lorentzian
 0
[    ( )  2
2
1 x
'2
2
 0 x
 0 2
a0 x 2
 2
(
) (
) ]
2
2
2
1 x
1 x
1 x
'
dispersion
neglected
6
Experimental Setup
Uranium Lamp
P
QW
L P
L
H
PMT
L
F
P
Lock-in
Amplifier
Neutral Density
Filter
Heat Pipe
P
Chopper
Lock-in
Amplifier
L
L
Computer
Chopper
BS
Ti-Sapphire
Laser
Dye Laser
Laser path
Electronics path
7
Excitation Scheme of the Rb2
Polarization Experiment
B1Πu
(2,70)
Fixed
frequency
pump laser
J’=74
72
70
68
•
The angular momentum
orientation of the molecules is
partially preserved during the
collision.
•
The collisionally populated
energy levels serve as probe
initial levels leading to satellite
transitions
A/b
scanning probe
laser
J”=73
69
X1Σg+ (0,71)
Collisionally populated levels
Previously used in: Kasahara, S. et al, J.
Chem. Phys. 111(1999)
8
Parent R and P lines to Scale With Collisional
Satellite Lines in the Rb2 Probe Laser Scan
12000
Intensith (Arbitruary Units)
11000
10000
P Lines
R Lines
9000
In subsequent scans the
collisional satellite lines
were recorded on a more
sensitive scale to enhance
the yield beyond the strong
R,P lines
8000
7000
6000
5000
4000
3000
2000
1000
0
11380
11390
11400
11410
wavenumber (cm-1)
11420
9
Probe Laser Scan of Rb2 Collisional
Satellite Lines
P:J"= 87
85
83
81
79
R: J"= 87
85
11380 11381 11382 11383 11384 11385 11386 11387
B1  u (2,70)  X 1 g (0,71)
10
Probe Laser Scan of Rb2 Including P(71) Parent Line
P:J"= 77
R:J"=
75
83
71
73
81
69
79
intensity= X100 X25
67
77
75
X5 X5
11388 11389 11390 11391 11392 11393 11394 11395
B1  u (2,70)  X 1 g (0,71)
11
Probe Laser Scan of Collisional Satellite
Lines of Rb2 Including R(71) Parent Line
P:J"=65
61
71
R:J"= 73
X10
11395
11396
X100
11397
59
55
57
69
X10
11398
67
X10
11399
53
65
51
47
49
63
61
X5
11400
11401
B1  u (2,70)  X 1 g (0,71)
11402
59
12
Probe Laser Scan of Satellite Lines of Rb2
17
P: J"=
45
43
R:J"= 57
41
55
39 37
53
35 33 31 29 27 25 23 21 19
51
49
47 45 43
15
41 39 37 35 33 31
29
27
25
23
21
19
17
15
13
11403
11404
11405
11406
11407
11408
11409
B1  u (2,70)  X 1 g (0,71)
11410
13
Rotational Energy Level Data from the Rb2
Polarization Experiment
• The DCM dye laser was tuned
to 14736.184 cm-1.
T-0.017J(J+1)
12200
12000
• Two transitions were pumped
simultaneously:
11800
B1u (2,70)  X 1g (0,71)
B1  u (2,85)  X 1 g (0,84)
11600
11400
0
2000
4000
6000
J(J+1)
8000
10000
12000
14
Spectra of the Cs2 Experiment
P 72
R 79
11040
71
70
78
69
77
11041
76
75
64
66
68
74
72
73
11042
71
62
70
11043
wavenumber (cm-1)
Pump transitions:
C1 Π u (7,73) X1 Σg (6,74)
and
C1 Π u (7,72) X1 Σg (6,73)
69
11044
15
Spectra of the Cs2 Experiment
74
P
80
79
78
77
76
75
R
11036
73
80
11037
11038
11039
wavenumber (cm-1)
Pump transitions:
C1 Π u (7,73) X1 Σg (6,74)
and
C1 Π u (7,72) X1 Σg (6,73)
11040
Logarithm of the
Franck-Condon Factors
V(X)=4
V(X)=5
V(X)=6
V(X)=7
0
-2
-0.5
-1.0
log10FCF
log10FCF
-4
-6
-8
-1.5
-2.0
-10
-2.5
-12
-14
11000
11100
11200
11300
11400
11500
Termvalues of the Cs2 A/b States (cm-1)
Calculated by Prof. T. Bergeman
Published in Phys. Rev. A 83, 032514 (2011)
16
-3.0
11400 11500 11600 11700 11800 11900 12000
Termvalues of the Rb2 A state (cm-1)
Calculated from the potential curves provided by
Dr. S. Kotochigova, Temple University
Cs2 rotational energy level data for the
A~b complex
13000
11500
LAC
Tsinghua
Innsbruck
Temple
12500
11400
17
11300
E-0.0091J(J+1)
T-0.0091J(J+1)
12000
11200
11100
11500
11000
10500
10000
11000
9500
2000
4000
6000
8000
10000
12000
14000
16000
J(J+1)
Cs2 polarization data of A~b states
from Temple University.
0
20000
40000
60000
J(J+1)
Cs2 polarization data of A~b states
from different sources.
80000
Theoretical Fit
Theoretical Calculation
Experimental Data
22000
11380
20000
11360
18000
Termvalues
E-0.0091J(J+1)
11400
11340
11320
b
A
24000
16000
14000
12000
10000
11300
8000
11280
5000
10000
15000
3
J(J+1)
Part of our fitted Cs2 data
4
5
6
7
9
R
Cs2 A~b potential curves fitted
from experimental data
Global deperturbation analysis by
Dr. T. Bergeman, SUNY; Dr. S. Kotochigova, Temple University;
Dr. A. Drozdova, Dr. E. Pazyuk, Dr. A. V. Stolyarov Moscow State University
Analysis published in Phys. Rev. A 83, 032514 (2011)
8
19
Conclusion
•
More than 2000 spectral lines for the Rb2 were observed and 881 of them
were assigned. More than 300 spectral lines for the Cs2 were observed and
assigned.
•
Collisional satellite lines with ΔJ up to 58 in Rb2 and up to 12 in Cs2 were
observed due to collision induced orientation transfer
•
This technique is very useful for enhancing the yield of rotational level data
beyond the customary R and P parent lines with ΔJ = ±1 for each pump
laser labeled lower level
•
This enhancement of polarization spectroscopy is important in cases where
it is difficult to identify spectrally ‘clean’ pump transitions involving only one
rovibronic transition. The spectroscopy of the heavier alkali molecules
benefits from this approach.
20
Acknowledgements
Prof. Tom Bergeman, Stony Brook
Dr. H. Salami
Dr. Amanda Ross, Lyon
and other co-authors who contributed to the subsequent
global deperturbation analysis of the A~b complex of
Rb2: Phys. Rev. A 80, 022515 (2009) and
Cs2: Phys. Rev. A 83, 032514 (2011)
Funded by NSF PHY 0555608, PHY 0855502, PHY 0652938
and PHY 0968898.
Funded by NSF PHY 0555608, PHY 0855502, PHY 0652938
and PHY 0968898.
Details about the Rb2 Experiment
•
•
•
•
•
Pump laser: DCM Dye Laser (30 mW)
Probe laser: TiSapphire Laser (4 mW)
Temperature: 480K
Argon gas pressure: 1 Torr at Room Temperature
Calibration: Pump Laser Calibrated by Iodine Lamp;
Probe Laser Calibrated by Uranium Lamp
Spectral Ranges of Lasers
Laser
Lasing Range
TiSapphire(MW)
781-943nm
KitonRed 620 Dye laser 598-645nm
Verdi Pump Laser
532 nm
DCM Dye Laser
625-700nm
Argon Pump Laser
514 nm
How to Make Circularly
Polarized Light
Alkali dimer density
Dimer
T(K)
P(Torr)
n(cm-3)
Rb2
480
8.112E-5
1.62E12
Cs2
550
5.94E-3
1.03E14