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

Motivation

Iridium containing molecules

•IrSi?

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

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

(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

(6,0)[16.0]1.5-X2D5/2 band

Observation (cont.)

Resolution ~30 MHz

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

Ready for Stark measurement & analysis

Stark effect (next slide)

Predicted spectra

2339 V/cm||

0V/cm

P(5/2) under applied electric field

1754 V/cm||

LIF

sig

nal

191P(11/2)

1169 V/cm||

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)

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

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

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

C (11.25eV)Si (8.15eV) Ir (9.0eV)

Difference in bonding IrSi and IrC

IrSi: Covalent bond

IrC: Ionic bond

Compare with other Ir - containing molecule

•IrP

•IrCl

•IrO

•IrS

Predict the reduced dipole moment of other Ir-containing molecule

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?)

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:

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