Transcript Puzzarini_SiH3F-ldip.ppt

SILYL FLUORIDE:
LAMB-DIP SPECTRA and
EQUILIBRIUM STRUCTURE
Cristina PUZZARINI and Gabriele CAZZOLI
Dipartimento di Chimica “G. Ciamician”, Università di Bologna
Jürgen GAUSS
Institut für Physikalische Chemie, University of Mainz
Columbus — June 26, 2009
1) Hyperfine Structure:
- Instrument & Technique
- Theory & Computations
1) Hyperfine Structure:
- Instrument & Technique
- Theory & Computations
MILLIMETER-WAVE EXPERIMENTAL SET-UP
BLOCK DIAGRAM OF THE 50-800 GHz SPECTROMETER
fG
InSb
DETECTOR
MULTIPLIER
GUNN
DIODES
THERMOSTAT
or liquid N2 system
fG
MIX
MULT
90 MHz
|fG - mfRF |
fRF
GUNN P. SUPPLY
and
SYNCR
ref: 73 MHz
20 MHz
|fRF - nfS|
HP8642A
SYNTH
RF OSCILL
3.7- 7.6 GHz
corr
MIX
ref
SYNCR
LOCK - IN
10 MHz
freq. standard
ref: 20 MHz
nfS
MULT
fS
PREAMPL
SYNTH
10 kHz-1 GHz
Measurements: Lamb-dip technique
Using free-space cell
Polarizer
Corner cube
mirror
Cell
Scheme of the radiation path
InSb detector
Frequency
modulated
source
G. Cazzoli & L. Dore, J. Mol. Spectrosc. 143, 231 (1990).
Measurements: Lamb-dip technique
 obs   0 1  v za / c 
 obs
-vza
 vz 
  0 1  
c 

 obs   0
1) Partial saturation
2) Only Doppler profile
3) Rad: back and forward
+vza
vz= 0
Measurements: Lamb-dip technique
C18O: J = 1-0
CH2BrF
28 kHz
Doppler
Doppler profile
Dip profile
Lamb-dip
539120
539125
539130
539135
FREQUENCY (MHz)
109782.0
109782.1
109782.2
Frequency (MHz)
109782.3
109782.4
539140
1) Hyperfine Structure:
- Instrument & Technique
- Theory & Computations
Parameters of Rotational Spectroscopy
Rotational Hamiltonian
Rotational constants
Effective Hamiltonian: determination of HRot via quantum chemistry
Parameters of Rotational Spectroscopy
Rotational Hamiltonian
Rotational constants
Nuclear quadrupole coupling constants
Effective Hamiltonian: determination of HRot via quantum chemistry
Parameters of Rotational Spectroscopy
Rotational Hamiltonian
Rotational constants
Spin-rotation interactions
Nuclear quadrupole coupling constants
Effective Hamiltonian: determination of HRot via quantum chemistry
Parameters of Rotational Spectroscopy
Rotational Hamiltonian
Rotational constants
Spin-rotation interactions
Nuclear quadrupole coupling constants
Spin-spin (direct)
interactions
Effective Hamiltonian: determination of HRot via quantum chemistry
Quantum-Chemical Calculation
of Spectroscopic Parameters
• Spin-rotation interaction
second-order property: requires second derivatives of energy
Quantum-Chemical Calculation
of Spectroscopic Parameters
• Spin-spin coupling
DIPOLAR SPIN-SPIN COUPLING TENSOR
requires equilibrium geometry: no „electronic property“
addditional contribution due to:
 indirect spin-spin coupling (usually negligible)
 vibrational corrections (anharmonic force field)
Beyond the Rigid-Rotator Approximation
COUPLING of ROTATIONAL and VIBRATIONAL MOTION
PERTURBATION THEORY starting from
the rigid-rotator harmonic oscillator approximation
 Vibrational corrections to properties:
KL
D KL  Deq


r
  D KL 
1

 Qr 
 Q 
2
r Q 0

  2 D KL 

 Qr Qs  ...
 Q Q 
r ,s 
r
s Q 0

Vibrational corrections require:
anharmonic force field calculations
Accurate hyperfine parameters
>>>> Main requirements:
- accurate method
- cc basis set
- CV corrections
- vibrational corrections
Accurate hyperfine parameters
>>>> Main requirements:
- accurate method [CCSD(T)]
- cc basis set
- CV corrections
- vibrational corrections
Accurate hyperfine parameters
>>>> Main requirements:
- accurate method [CCSD(T)]
- cc basis set [nQ]
- CV corrections
- vibrational corrections
Accurate hyperfine parameters
>>>> Main requirements:
- accurate method [CCSD(T)]
- cc basis set [nQ]
- CV corrections [additivity/CV bases]
- vibrational corrections
Accurate hyperfine parameters
>>>> Main requirements:
- accurate method [CCSD(T)]
- cc basis set [nQ]
- CV corrections [additivity/CV bases]
- vibrational corrections [ff: -correlated
method
-basis: nT]
1) Hyperfine Structure:
- Instrument & Technique
- Theory & Computations
28SiH F
3
(values in kHz)
F
Theory
CN (Cxx=Cyy)
2.71
CK (Czz)
44.94
H
Cxx
0.64
Cyy
-1.19
THEORY: C
-6.64
zz
Equilibrium:
Cxz (ae)CCSD(T)/aug-cc-pCVQZ
0.60
Vib. Corrections:
(ae)CCSD(T)/cc-pCVTZ
Czx
3.03
H-F -3D1 (1.5
-11.36
CDFOUR
:
zz)
-0.5D2 ((Dxx-Dyy)/4)
-1.75
http://www.cfour.de
H-H 1.5D3 (1.5 Dzz)
12.46
28SiH
3F
J = 15 - 14, K = 13
only F
F + H
EXP
429150.50
429150.55
FREQUENCY (MHz)
429150.60
28SiH
3F
J = 15 - 14, K = 13
only F
F + H
EXP
429150.50
429150.55
FREQUENCY (MHz)
429150.60
(values in kHz)
F
28SiH F
3
Theory
CN (Cxx=Cyy)
CK (Czz)
H
Cxx
Cyy
Czz
Cxz
Czx
H-F -3D1 (1.5 Dzz)
-0.5D2 ((Dxx-Dyy)/4)
H-H 1.5D3 (1.5 Dzz)
2.71
44.94
0.64
-1.19
-6.64
0.60
3.03
-11.36
-1.75
12.46
Experiment
2.71fixed
45.74(35)








29SiH
3F
(Values in kHz)
F
Si
H
THEORY:
CN (Cxx=Cyy)
Theory
2.69
CK (Czz)
44.93
CN (Cxx=Cyy)
-8.89
CK (Czz)
-41.89
Cxx
0.63
Cyy
-1.18
Czz
-6.64
1.5D3 (1.5 Dzz)
16.45
Equilibrium: Cxz(ae)CCSD(T)/aug-cc-pCVQZ
0.59
Czx
3.03
Vib. Corrections:
(ae)CCSD(T)/cc-pCVTZ
F-Si
C
:
-7.46
-0.5D ((D -D )/4)
4.84
http://www.cfour.de
Si-H
-3D (1.5 D )
-11.30
F-H
-3D1 (1.5 FOUR
Dzz)
2
1
H-H
xx
yy
zz
-0.5D2 ((Dxx-Dyy)/4)
-1.73
1.5D3 (1.5 Dzz)
12.42
29SiH
3F
J = 15 - 14, K =13
only F
29
F +
F +
425220.35
425220.40
425220.45
FREQUENCY (MHz)
425220.50
Si
29
Si + H
29SiH
3F
J = 15 - 14, K =13
only F
29
F +
F +
Si
29
Si + H
EXP
recorded in natural abundance
425220.35
425220.40
425220.45
FREQUENCY (MHz)
425220.50
30SiH
(values in kHz)
F
CN (Cxx=Cyy)
CK (Czz)
3F
Theory
2.23
45.46
THEORY:
Equilibrium: (ae)CCSD(T)/aug-cc-pCVQZ
Vib. Corrections: (ae)CCSD(T)/cc-pCVTZ
CFOUR:
http://www.cfour.de
30SiH
3F
J = 14 - 13, K = 9
hfs due to F
(mod=15 kHz)
hfs due to F
(mod=30 kHz)
393942.75
393942.80
FREQUENCY (MHz)
30SiH
3F
J = 14 - 13, K = 9
hfs due to F
(mod=15 kHz)
hfs due to F
(mod=30 kHz)
EXP
recorded in natural abundance
393942.75
393942.80
FREQUENCY (MHz)
2) Equilibrium Structure:
- semi-exp structure
- pure ab initio structure
2) Equilibrium Structure:
- semi-exp structure
- pure ab initio structure
Empirical equilibrium structure
1
B
Be  B0    r
2 r
from EXPERIMENT
(various isotopic species)
From THEORY
(cubic force field)
B0 from EXPERIMENT
(various isotopic species)
Actual FIT:
moments of inertia
1)
2)
3)
4)
5)
6)
7)
8)
28SiH
3F:
A0 & B0
28SiD F: A & B
3
0
0
29SiH F: B
3
0
29SiD F: B
3
0
30SiH F: B
3
0
30SiD F: B
3
0
28SiHD F: A , B
2
0
0
28SiH DF: A , B
2
0
0
Vibrational Corrections from THEORY
(cubic force field: (all)CCSD(T)/CVTZ)
- harmonic ff: analytic 2nd deriv. of E
- anharmonic part: numerical differ.
&
&
C0
C0
Computation of Cubic and Quartic Force Fields
• cubic force fields:
THEORY:
Cubic Force
Field:
single
numerical differentiation along
(ae)CCSD(T)/cc-pCVTZ
qr
• quartic force fields:
CFOUR:
http://www.cfour.de
double numerical differentiation along qr
Schneider & Thiel, Chem. Phys. Lett. 157, 367 (1989)
Stanton et al., J. Chem. Phys. 108, 7190 (1998)
2) Equilibrium Structure:
- semi-exp structure
- pure ab initio structure
Best estimated equilibrium structure
- geometry optimization:
dEtot dE  ( HF  SCF ) dE  (CCSD(T ) dE(core)



dx
dx
dx
dx
(bases: cc-pVn Z, n =Q,5,6; cc-pCV5Z)
- full-T corrections:
(basis: cc-pVTZ)
r( full  T )  r(CCSDT )  r(CCSD(T ))
- pert-Q corrections:
(basis: cc-pVDZ)
r ((Q))  r (CCSDT (Q))  r (CCSDT )
- on the whole:
re (best )  r ( Etot )  r ( full  T )  r ((Q))
2) Equilibrium Structure:
- semi-exp structure
- pure ab initio structure
Pure ab initio equilibrium structure:
basis set convergence and higher excitations
(dist: Å / ang: º)
F-Si
Si-H
HSiF
CCSD(T)/VQZ
1.6007
1.4755
108.34
CCSD(T)/V5Z
1.5970
1.4745
108.34
CCSD(T)/V6Z
1.5963
1.4744
108.33
CBS
1.5961
1.4744
108.31
CBS+CV
1.5909
1.4699
108.31
CBS+CV+full-T
1.5911
1.4701
108.31
CBS+CV+full-T+(Q)
1.5915
1.4702
108.32
EQUILIBRIUM STRUCTURE:
pure ab initio structure
vs
semi-experimental geometry
(dist: Å / ang: º)
F-Si
Si-H
HSiF
CBS+CV+full-T+(Q)
1.5915
1.4702
108.32
Semi-experimental
1.5906(1)
1.4698(2)
108.29(2)
[uncertainties: 3]
THANK YOU for your attention!!