Gerrit C. Groenenboom Institute of Theoretical Chemistry ...
Transcript of Gerrit C. Groenenboom Institute of Theoretical Chemistry ...
Applications of cold polar moleculesGerrit C. Groenenboom
Institute of Theoretical Chemistry
University of Nijmegen
The Netherlands
Missoula, May 2006 – p. 1/35
Collaborators
Nijmegen, NetherlandsAd van der AvoirdGuillaume DhontMark van der LooGerrit Groenenboom
ITAMP, HarvardAlex DalgarnoBalakrishnanRoman KremsXi Chu
UtrechtJoop van Lenthe
Berlin, GermanyGerard MeijerBas van de MeerakkerSteven HoekstraJoop GilijamseNicolas Vanhaecke
Missoula, May 2006 – p. 2/35
Introduction
Buffer gas cooling and magnetic trapping3He+CaH(2Σ+), cooling+trapping, Doyle group, 19983He+NH(3Σ−), cooling, Doyle group, 20043He+OH(2Π3/2)
Stark deceleration
Radiative lifetime of trapped OH(v = 1)
Collisions of Xe with Stark controlled OH(2Π3/2f )
NH(3Σ−)+NH(3Σ−) potentials, bound states.Chemistry?
Missoula, May 2006 – p. 3/35
Ab initio calculations
RCCSD(T) method (MOLPRO)
One electron basis:
CaH(2Σ+)–He d-aug-cc-pVTZ; Ca: 6-311G++(3df)NH(3Σ−)–He aug-cc-pVQZOH(2Π)–He aug-cc-pVTZ (A′ and A′′ PES)OH(2Π)–Xe aug-cc-pVQZ (A′ and A′′ PES) [256 orbitals]
+ bond orbitals
Xe: ECP28MDF_AVQZ, Kirk Peterson et al. JCP (2003)
Xe: (5s)2(5p)6 in CCSD(T), polarizability within 1%
Missoula, May 2006 – p. 4/35
Jacobi coordinates
Θ
R
rHCa
He
Missoula, May 2006 – p. 5/35
He-CaH (2Σ+) potential (cm−1)
R (a0)
−1
−2−4−6−8
−10
−2
8
1632
6410
020
0
500
500 100
θ (d
eg)
6 8 10 12 140
30
60
90
120
150
180
G. C. Groenenboom and N. Balakrishnan, J. Chem. Phys., 118, 7380 (2003)
Missoula, May 2006 – p. 6/35
He–NH (3Σ−) potential (cm−1)
5 6 7 8 9 10 11 120
30
60
90
120
150
180
θ (d
egre
es)
R (a0)
−1
−3−5
−7−9
−11
−13−15
−17
−19
−15
−11
020
6010
0
H. Cybulski, R. V. Krems, H. R. Sadeghpour, A. Dalgarno, J. Klos, G. C. Groenenboom, A.
van der Avoird, D. Zgid, and G. Chalasinski, J. Chem. Phys., 122, 094307 (2005) Missoula, May 2006 – p. 7/35
He–OH(2Π) potentials (cm−1)
4 5 6 7 8 9 100
30
60
90
120
150
180
−27
−24
−21
−21
−18
−18
−15
−15−12
−12
−9 −9
−6
−6
−3
−3
0
50
100
150200
250
300
350
400
450
500
R (a0)
θ (d
egre
es)
He−OH (A’)
4 5 6 7 8 9 100
30
60
90
120
150
180
−24
−21
−21
−18
−18
−15
−15
−12
−12
−9
−9
−6
−6
−3
−3
0
50100
150200
250
300350
400450
500
R (a0)
θ (d
egre
es)
He−OH (A’’)
H.-S. Lee, A. McCoy, R. Toczyłowski, and S. M. Cybulski, J. Chem. Phys. 113, 5736 (2000)
Missoula, May 2006 – p. 8/35
Xe–OH(2Π) potentials (cm−1)
4 6 8 10 120
30
60
90
120
150
180
R (a0)
θ (d
egre
es)
Xe−OH (A’)
−200−175
−150−
125−
100−
75
−50
−25
1450
450
850
650
50
5 6 7 8 9 10 11 120
30
60
90
120
150
180
R (a0)
θ (d
egre
es)
Xe−OH (A’’)
−200
−175−150
−125−100
−100
−75
−50
−25
−75
50
1450
450850
Missoula, May 2006 – p. 9/35
Zeeman interaction (2Σ)
0 1 2 3 4−2
−1
0
1
2
B/tesla
Ene
rgy/
cm−
1
|S,MS> = |1/2, 1/2>
|S,MS> = |1/2, −1/2>
σinelastic
(Spin−flipping)
HZeeman = −µ ·B
µ = − e2m(L + geS)
state |µ|
CaH 2Σ+ 1µB
NH 3Σ− 2µB
OH 2Π3/2 1.4µB
Elastic momentum transfer cross section:
σtr(E) = 2π
∫ π
0
dσ(E)
d cos χ(1− cos χ)d cos χ
Missoula, May 2006 – p. 10/35
He–CaH: coupled channel calculation
Hamiltonian:
H = −~
2
2µR
d2
dR2R +
l2
2µR2+
N2
2µCaHr2+ V (R, re, θ) + VSR
Spin-rotation term:
VSR = γN · S (γ = 0.0415 cm−1)
Channel basis:|NMN 〉|SMS〉|lml〉
Missoula, May 2006 – p. 11/35
He–CaH: modified potential
Spherically averaged potential
8 12 16 20R (a0)
−5
0
5
Ene
rgy
(cm−
1 )
Original potentialModified potential (f=0.15)
V = V CCSD(T) + f × (V CCSD(T) − V CCSD)
f = 0.15: van der Waals minimum 3% more attractive
Missoula, May 2006 – p. 12/35
3He–CaH(N=0): elastic cross sections
10−3
10−2
10−1
100
101
Kinetic energy (cm−1
)
102
103
104
105
Cro
ss s
ectio
n (1
0−16
cm
2 )originalmodified (f=0.1)modified (f=0.15)
Missoula, May 2006 – p. 13/35
3He–CaH: comparison with experimentThermal averaged elastic momentum transfer cross section
0.0 0.2 0.4 0.6 0.8 1.0Temperature (K)
10−14
10−13
Theory (modified potential)TheoryExperiment
Cro
ss s
ectio
n (c
m2 )
σtr(E) = 2π
∫ 2π
0
dσ(E)
d cos χ(1− cos χ)d cos χ
Experiment: J. D. Weinstein et al., Nature 395, 148 (1998)
Missoula, May 2006 – p. 14/35
3He+CaH: Spin-flipping
VSR = γN · S
1/2j =
N = 1
0N =
j = 3/2
j = 1/2
Phys. Rev. A, 67, 060703 (2003)
Missoula, May 2006 – p. 15/35
3He+CaH(N = 0): spin flip cross sections
10−6
10−5
10−4
10−3
10−2
10−1
100
Collision energy (cm−1
)
10−15
10−12
10−9
10−6
10−3
100
103
Cro
ss s
ectio
n (Å
2 )
k(T = 0.4K) = 〈σv〉 = 1.65×10−14 cm3s−1 (with resonance)
1.20×10−17 cm3s−1 (modified potential)
Experiment: k(0.4K) ≈ 10−17 cm3 s−1
Missoula, May 2006 – p. 16/35
3He-NH(3Σ−): (in)elastic cross sections
(B = 100 G = 0.01 T)
10−6
10−4
10−2
100
102
Collision energy (cm−1
)
10−11
10−9
10−7
10−5
10−3
10−1
101
103
Cro
ss s
ectio
n (Å
2 )
← elastic
← inelastic
← without the N = 2 level
Effect of omitting γN · S is negligible
Missoula, May 2006 – p. 17/35
3He+OH(2Π3/2): (in)elastic cross sections
10−6
10−5
10−4
10−3
10−2
10−1
100
101
10−10
10−8
10−6
10−4
10−2
100
102
104
Collision energy (cm−1)
Cro
ss s
ectio
n (A
ng2 )
3He+OH
Elastic, B=0 T
B=0 T
B=2 T
B=0.5 T
B=0.01 T
B=0.1 T
Missoula, May 2006 – p. 18/35
3He+OH(2Π3/2): (in)elastic cross sections
10−1
100
100
101
102
103
E (cm−1)
σ (Å
2 )
B=0 T
B=0.1 T
B=2 T
Missoula, May 2006 – p. 19/35
Stark decelerator
H.L. Bethlem, G. Berden, and G. Meijer, Phys. Rev. Lett. 83, 1558 (1999).
Missoula, May 2006 – p. 20/35
Stark decelerator
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
Missoula, May 2006 – p. 21/35
Missoula, May 2006 – p. 22/35
Radiative lifetime of OH[X2Π3/2(v = 1)]
S. van de Meerakker, N. Vanhaecke, M. van der Loo, G. Groenenboom, and G. Meijer, Phys.
Rev. Lett., 95, 013003 (2005)
Missoula, May 2006 – p. 23/35
Calculation
0.5 1 1.5 2 2.5
−5
0
5
10
Pot
entia
l Ene
rgy
(eV
)
O−H distance (Å)
v=0v=1
⟨µz⟩
OH(X2Π)
0.5 1 1.5 2 2.5
−1
−0.5
0
0.5
1
1.5
2
Dip
ole
Mom
ent (
Deb
ye)
Energy 0.02%
Dipole 0.7%
aug-cc-pV6Z, µz withaug-cc-pVQZ
1σ − 5σ, 1π − 2π CASSCF
Internally contractedSD-MRCI
Special relativistic effects atDouglas-Kroll one-electronlevel
Λ-type doubling, spin-orbit,spin-rotation,rotation-vibration
Field induced parity mixing
Missoula, May 2006 – p. 24/35
Radiative lifetime of OH[X2Π3/2(v = 1)]
τ−1 =∑
f Afi
Method Afi τ (ms) ε(τ) (ms)
HITRAN Q(T )
e−βEi−e−βEf
ω2
Iaπ2c2gfSfi 56.6 ±5.6 · · · ± 11.3
Decay in trap 59.0 ±2
Calculation 4αω3
fi
3c2e2 |〈f |µ|i〉|2 58.0 ±1
Missoula, May 2006 – p. 25/35
Xe+OH(2Π3/2f ) collision experiment
pulsed valve
hexapole
skimmer
Stark decelerator
LIF zone
PMT
photodissociation
laser (193 nm)
detection laser
(282 nm)
Xe
cooled -70o C
Bas van de Meerakker, Steven Hoekstra, Joop Gilijamse, Gerard Meijer (Berlin)
Missoula, May 2006 – p. 26/35
OH energy levels
0
50
100
150
200
250
1 3/2
2 5/2
3 7/2
1 1/2
2 3/2
N J
N J
cm-1
ef
ef
ef
ef
ef
+-
+- +
-
-+
-+
ε p
ε p
F1, X 2Π3/2
F2, X 2Π1/2
Missoula, May 2006 – p. 27/35
Xe-OH energy dependent cross sections
Xe-OH 2Π3/2(J′ = 3/2, f)→ Xe-OH 2Π3/2,1/2(J, e/f)
0 200 400 600 800
100
101
102
103
3/2f
3/2e
5/2e
5/2f
1/2e
E (cm−1)
σ (a
02 )
Xe−OH
Missoula, May 2006 – p. 28/35
Xe+OH, relative cross section
Missoula, May 2006 – p. 29/35
Xe+OH cross sections at 130 cm−1
Xe-OH 2Π3/2(J′ = 3/2, f)→ Xe-OH 2Π3/2,1/2(J, ǫ)
J, ǫ experiment (%) calculation (%)3/2, e 59± 4 61.55/2, e 26± 2 24.35/2, f 11± 2 13.41/2, e 1.5± 0.5 0.311/2, f 1.5± 0.5 0.44
Missoula, May 2006 – p. 30/35
NH(3Σ−)–NH(3Σ−)
SA = 1 and SB = 1⇒ S = 0, 1, 2
S = 0: chemically stable molecule
S = 1: idem, in triplet excited state H
H
N N
Ab initio calculations
S = 2 potential by RCCSD(T) method
Differences between S = 1 and S = 0 potentials andS = 2 potential by CAS-PT2 or CAS-PT3
G. S. F. Dhont, J. H. van Lenthe, G. C. Groenenboom, and A. van der Avoird,
J. Chem. Phys., 123, 184302 (2005)
Missoula, May 2006 – p. 31/35
N2H2 (diimide, diazene) chemistry
0
20
40
60
80
100
120
kcal
/mol +
+
+
C.-H. Lai et al., J. Phys. Chem., 107, 2700 (2003)
Missoula, May 2006 – p. 32/35
NH–NH potential, all three angles optimized
5.5 6 6.5 7 7.5 8 8.5 9−1000
−900
−800
−700
−600
−500
−400
−300
R (a0)
Pot
entia
l (cm
−1 )
S = 2
S = 1
S = 0
θA = θB = 0◦
θA, θB ≈ 90◦
Missoula, May 2006 – p. 33/35
NH–NH bound levels onS = 2 potential
0 1 2 3 0 1 2 3−400
−350
−300
−250
−200
A1
B1
A1
B1
B1
A1
B1
A1
0, 0, 0
1, 0, 00, 1, 0
0, 1,−12, 0, 01, 1, 0
0, 1, 1 + 0, 2, 00, 1, 0
0, 1, 0
1, 1, 00, 1, 1 + 0, 2, 00, 1, 0
J J
Ene
rgy
(cm
−1 )
Label : vs, k
A, k
B
Missoula, May 2006 – p. 34/35
Summary
buffer gas cooling
He+CaH(2Σ+): well understoodHe+NH(3Σ−): predicted favorableHe+OH(2Π3/2): predicted unfavorable
Stark decelerationOH (v = 1) life time: reduced error barXe+OH(2Π): high energy resolution scattering
NH(3Σ−)+NH(3Σ−): ultracold chemistry ?
Missoula, May 2006 – p. 35/35