![Page 1: Anh T. Le and Timothy C. Steimle The electric dipole moment of Iridium monosilicide, IrSi Department of Chemistry and Biochemistry, Arizona State University,](https://reader030.vdocuments.mx/reader030/viewer/2022032707/56649e2e5503460f94b1e669/html5/thumbnails/1.jpg)
Anh T. Le and Timothy C. Steimle
The electric dipole moment of Iridium monosilicide, IrSi
Department of Chemistry and Biochemistry, Arizona State
University,Tempe, AZ 85287
Lan Cheng and John F. StantonThe University of Texas at Austin,
Austin,TX 78712-0165.
Michael D. Morse and Maria A. Garcia Department of Chemistry,
University of Utah, Salt Lake City, UT 84112, USA
The 68th International Symposium on Molecular Spectroscopy, June
2013
Funded by DoE-BES
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Motivation
Iridium containing molecules
•IrSi?
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Previous work
*
•Prof Morse’s group: Recorded 31 electronic bands
Recorded high resolution LIF of the (6,0)[16.0]1.5 - X2D5/2
bands for 191&193IrSi (lowest angular momentum quantum
number)
Analyzed, determined the fine and hyperfine parameters Recorded & Analyzed Stark spectra to determine the
molecular dipole moments for the X2D5/2 and [16.0]1.5(v=6)
states
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Experiment method
Ablation laser
CW dye laser
Skimmer
Stark Plates
Well collimatedmolecular beamRot.Temp.<20 K
Electric field ~ 4000 V/cmResolution ~30 MHz
Gated photon counter
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(6,0)[16.0]1.5-X2D5/2 band
Large isotopic shifts (1.5cm-1) between 191IrSi, 193IrSi Formed a head quickly due to large difference in rotational constantsHighly overlapped
Complicated spectrum
Observation
Need to understand the field free spectrum to be able to study the Stark spectra
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(6,0)[16.0]1.5-X2D5/2 band
Observation (cont.)
Resolution ~30 MHz
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1. Effective Hamiltonian
Heff = Hso+ Hrot + Hmhf(Ir)+ HeQq(Ir)
Modeling the (6,0)[16.0]1.5-X2D5/2 band system
Ir(I=3/2)
Parameters: B, h5/2(191,193Ir) and eQq0(191,193Ir) for the
X2D5/2(v=0) state,T00, B, h3/2(191,193Ir) and eQq0(191,193Ir) for the
(6,0)[16.0]1.5
2. 16x16 Matrix representation: Hund’s case (abJ) coupled
basis set: Eigenvalues & Eigenvectors
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Ready for Stark measurement & analysis
Stark effect (next slide)
Predicted spectra
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2339 V/cm||
0V/cm
P(5/2) under applied electric field
1754 V/cm||
LIF
sig
nal
191P(11/2)
1169 V/cm||
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Facing the Challenge
•9 field free transitions in
P(5/2) splits into ~30 intense
DMJ= DMF transitions, and
numerous weaker DMJ DMF
transitions under applied
electric field•Fully resolved at voltage
higher than 4000V/cm
(impossible)
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What to expect?
m(X2D5/2)=1.60(7) D
1. Comparison with isovalent IrC
2. Electronegativity
Si (8.15eV)<Ir (9.0eV) Possible to have small negative dipole moment
Expect small positive dipole moment
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Predictedspectra
Stark spectra of IrSi
193IrSi, P(5/2)
1754 V/cm||
LIF
sig
nal
AB
C,D
c b a
A B C D
a b c
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m(X2D5/2)=-0.414 (6)Dm([16.0]1.5(v=6))=0.782(6)D
m(X2D5/2)=+0.414(6)Dm([16.0]1.5(v=6))=-0.782(6)D
Predicted spectraLIF
sig
nal
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C (11.25eV)Si (8.15eV) Ir (9.0eV)
Difference in bonding IrSi and IrC
IrSi: Covalent bond
IrC: Ionic bond
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Compare with other Ir - containing molecule
•IrP
•IrCl
•IrO
•IrS
Predict the reduced dipole moment of other Ir-containing molecule
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Summary
Recorded high resolution LIF of the (6,0)[16.0]1.5 -
X2D5/2 bands for 191&193IrSi
Analyzed, determined the fine and hyperfine
parameters Recorded & Analyzed Stark spectra to determine the
molecular dipole moments for the X2D5/2 and
[16.0]1.5(v=6) states
Compared reduce dipole moment of other Ir-containing
molecules with IrSiPredict the reduced dipole moment of other Ir-
containing molecule
High level relativistic calculations are in good
agreement with observed dipole moment and eQq0
(mag. hyperfine?)
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Thank you
DoE-BESFunding sources:
Prof. Michael Morse (University of Utah) –IrSi
Prof. John Stanton, Dr. Lan Cheng (U.Texas-Austin) -IrSi
Collaborations:
Fang Wang
Ruohan Zhang
Advisor: Prof. Timothy C. Steimle
Group members:
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Stark spectra of IrSi
m(X2D5/2)=-0.4139(64) D
m([16.0]1.5(v=6))=0.7821(63) D
Determined
dipole moments of IrSi
Comparison
Isovalent IrC
m(X2D5/2)=1.60(7) D
X25/2 : 12 14 22 1332X25/2 : 12 14 22 13 32
Why? next slide