Transcript 2006-OSU(zhong).ppt

Optical Zeeman Spectroscopy
of Iron Monohydride, FeH
Jinhai Chen, Timothy C. Steimle
Department of Chemistry and Biochemistry,
Arizona State University
Zhong Wang, Trevor J. Sears
Department of Chemistry,
Brookhaven National Laboratory
Introduction
FeH has long been a molecule of interest to the astrophysical
community and was first identified from features in the blue
and green regions of the visible spectrum of the sun.

P. K. Carroll and P. McCormack, AstroPhys. J. Letts. 177, L33 (1972).
The electronic spectrum of the FeH molecule is by far the
most extensively studied of those for all of the diatomic 3dtransition metal hydrides.
Previous Studies
FIG. 1. The known and
predicted low-lying electronic
states of FeH below 25 000 cm-1 .
Red lines indicate states accessed
experimentally; these are at their
empirically determined term
values.
The transitions indicated are
those which have been
investigated at high resolution
in previous work.
J. G. Phillips, S. P. Davis, B. Lindgren, and W. J. Balfour,AstroPhys. J. Suppl. Ser. 65, 721(1987)
Why measure the Zeeman effect

Solar spectra show the unusual rational line
shapes.

It has been understood to be due to the local
magnetic field in sunspots.

The FeH spectrum has been proposed as a
probe for estimation of the magnetic fields in
cooler stars and sub-stellar objects.
Our Work
the Zeeman effect in a number of
transitions involving low-J levels in the
(1,0) band of the F4Δi − X4Δi band
system (g-factors)
High Resolution Beam Spectroscopy Machine
High-resolution spectrometer
Helmholtz coils
Results
The Q(3.5) line in the (1,0) band of
the F47/2 – X47/2 transition of FeH
Figure 2.
The Q(3.5) line
observed
(A) field free;
(B) in the
presence of a
magnetic field
strength of 475
Gauss orientated
perpendicular
(ΔMJ = ± 1) to
the laser field.
ΔMJ = ±1
MI = ±0.5, ΔMI = 0
Figure 3.
The Q(3.5) line
observed
(A) field free;
(B) in the
presence of a
magnetic field
strength of 530
Gauss orientated
parallel (ΔMJ = 0)
to the laser field.
ΔMJ = 0
Analysis
The interaction with the static Zeeman field was modeled
using the conventional Zeeman Hamiltonian:
: the magnetic field vector;
: the orbital momentum vector;
: the spin momentum vector.
The matrix representation of HZ is diagonal in the projection
quantum number MF , but of infinite dimension.
Modeling the Zeeman Effect
Field-free Matrix
Non-parity Basis functions:
Y = | nL; SS; JWIFMF>
S =  3/2, L=  2 & W =  7/2
HZeeman
Hij =Term value
(the eight Hund case (aJ))
HZeeman
HZeeman= -mB
(the twelve Hund case (aJ))
The (ν= 0) X4Δ7/2 Laser Magnetic Resonance energy levels.
J. M. Brown, H. Korsgen, S. P. Beaton, and K. M. Evenson, J. Chem. Phys. (2006), to be published.
The gS was fixed to 2.002.
A non-linear least squares fitting procedure is used to
optimize the values of gL for the (v =1)F47/2 state.
The optimized values of gL is 1.079 and the standard
deviation of the fit was 24.5 MHz, which is commensurate
with measurement uncertainly of spectral shifts.
Figure 3
The Q(3.5) line observed (lower) and predicted (upper) in the presence of a
magnetic field of (1) 475 Gauss orientated perpendicular and (2) 530 Gauss
orientated parallel of the laser field spectra.
(1)
(2)
Summary
 The first laboratory measurements of the Zeeman
splittings in the Q(3.5) line of the (1,0) band of the
F4 – X4 transition of FeH have been modelled
using a traditional effective Hamiltonian.
 The upper-state g-factors obtained for the J = 3.5
level. The determined magnetic gL-factor is 1.079(8)
when the gS-factor is constrained to 2.002.
 The determined parameters can be used to predict
the magnetic tuning of features in this band in
sunspot spectra. ( Work in progress)
Acknowledgement


Steimle Group,
Department of Chemistry & Biochemistry,
Arizona State University
(Thanks for Wilton Virgo and Tongmei Ma’s helps)
Gas-phase Molecular Dynamics group,
Department of Chemistry,
Brookhaven National Laboratory, U.S.
$$ National Science Foundation, Experimental Physical Chemistry Division.
$$ Division of Chemical Sciences, Office of Basic Energy Sciences.
Thanks for your attention !
Electromagnet for Zeeman
spectroscopy (56G-1.2kG)
Mirror
‘‘MB,’’ molecular beam; ‘‘LB,’’ tunable laser radiation beam; ‘‘C,’’ Helmholtz coil;
‘‘IC,’’ iron core; ‘‘PMT,’’ cooled photomultiplier tube; ‘‘BPF,’’ band pass filter; ‘‘L,’’
lens; ‘‘M,’’ mirror.