Stark Study of the F4X47/2 (1,0) band of FeH

Jinhai Chen and Timothy C. SteimleDept. of Chemistry& BioChem, Arizona State University,

Tempe, AZ, 85287-1604

Jeremy J. Harrison and John M. BrownPhysical and Theoretical Chemistry, University of Oxford

Oxford, United Kingdom

Supported by National Science Foundation – Exp. Phys. Chem.

Published: JCP 124 184307/1-184307/7 (2006)

Motivation Determination of ground and excited state

permanent electric dipole moments,

Insight into metal-H bonding from establishing trends: TiH (X43/2:2.455(3)D)a NiH( X45/2:2.4(1)D)b

a) T.C. Steimle, J. E. Shirley, B. Simard, M. Vasseur, and P. Hackett, J. Chem. Phys. 95, 7179 (1991).

b) J.A. Gray, S.F. Rice, and R. W. Field, J. Chem. Phys. 82, 4717 (1985).

Most fundamental electrostatic property; used for intensity conc. conversion & other phenomena

Benchmark data for electronic structure calculations

Extensively studied in part due to its presence in stellar spectra

FeH pref erent ially f ound in cool regions assoc. with sunspots.

FeH

}History of Visible & NIR Spectroscopy of FeH

NIR-Fourier Transform emission:

a) Phillips et al ApJ Supp. 65, 721 (1987).

b) Dulick et al ApJ 594 651 (2003)

c) Balfour et al J. Chem. Phys. 121, 7735 (2004)

Laser Magnetic Resonance

a) Pure rot; Ken Evenson group JCP 89 4446 (1988)

b) Vib-rot: Evenson &Brown JCP (in press)

Visible Spectroscopy

a) Numerous studies by John Brown’s group

Conclusion: The energy levels of the F4 & X4 states can not be modeled using effective Hamiltonian (severe B-O breakdown)!

Previous spectroscopic studies

The Challenges of NIR Stark Study of FeH

1. No previously known mol. beam generation technique.

2. Fluorescence detection inefficient (1,0) (0,0)

Pulse valve/ablation source & Mol. Beam Machine

Field- f ree Observation high resolution Q(3.5) line

Proton Mag. Hyperfine splitting (Not previously observed)

}

35 MHz FWHM

Field- f ree ObservationHigh resolution P(4.5) Line

X & F State Doubling

Calc

J-dependence of -doubling in the (v=1) F47/2

State

ELD=[DJ(J+1)](J2-0.25)(J2-2.25)(J2-6.25)(J+3.5)

Stark effect on the Q(3.5) Line-Parallel Polarization

Stark effect on Q(3.5) Line-Perpendicular Polarization

Modeling Stark Effect in J=3.5 levels of X47/2 state

Field-free Matrix

Basis: nSJIFMF> with =3/2, 2 & = 7/2

HStark

HStark

HStark= -E

Numerical diagonalization Eigenvalues &vectorsSimilar approach for Stark effect in F47/2 state

Hij =Term value

Results

Obs.

(v=1) F47/2 1.29(3)D

(v=0) X47/2 2.63(3)D

Calc A

2.43 D

2.59 D

A:CASSCF-MRCPS(4) Tanaka et al JCP 115 4558 (2001)

Calc B

0.329 D

1.899 D

B:CASSCF/MRCI Z. Wang, T. Sears &J. Muckerman (in preparation)C:CASSCF/CI-NO iteration Chong et al JCP 85, 2850 (1986)

Calc C

2.9.2 D

Calc E

3.77 D

E: Pseudopotential Dolg et al JCP 86, 2123 (1987)

Rationalizing why (X4) >> (F4)

Two bonding mechanisms:

i) Fe(3d74s) + H(1s) bond formation

ii) Fe(3d64s2) 4s/5p hybridization+ H(1s) bond + occupied 4s/5p hybrid

Evidently Fe(3d64s2) is more important in the F4 state.

Thanks to:

Brookhaven group for providing Ab Initio predications

You for your attendance!

Summary:

1) Generated the first molecular beam of FeH

2) Determined in X4 & F4states

NSF- $