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Application of Sputtering Method
to the Observation of Rotational Spectra
of Metal-containing Molecules
M.Tanimoto , E.Y.Okabayashi , F.Koto , T.Okabayashi
Shizuoka University
Introduction
Transition Metal Compounds



Catalysis
Astrophysics
New Material
Spectroscopic study : difficult



High melting point (involatile)
Quantum chemical calculation difficult
d-electrons
high spin multiplicity
high orbital angular momentum
complicated electronic structure
High Resolution Spectroscopy
Formation of transient transition metal compounds
1.Vaporization (High Temperature Cell)
Up to 2000 degree C possible
 High density

2.Discharge of volatile compounds (e.g. Fe(CO)5)
Expensive , often toxic
 Reaction conditions difficult to select

3.Laser ablation
Used in combination with FTMW
 Not suitable for our spectrometer (low concentration)

4.Sputtering reaction
Fe + H2S
FeS
Experimental Set-up
AlCl3 + He
discharge
AlCl
Power Supply
liq.N2
pump
multiplier
InSb
Heater
Amp.
klystron
PSD
He
PC
Unknown species
6 lines
equal intensity
rather wide separation
High spin state , possibility of metal compound
Electrode (stainless steel : Fe , Ni , Cr)
CrCl
Sputtering from electrode material
After observing CrCl
FeCl : 6Di
2 lowest spin substate of W
(W= 9/2 , 7/2)
Linewidth
FeCl < CrCl
dipole moment
FeCl < CrCl
Stainless Steel
Fe : Cr = 80 : 18
Electronic Structure of the NiX radicals
–1
(cm )
4000
NiF
NiCl
NiBr
NiI
2
D3/2
2224
2000
2 +

1574
1768
1646
2 +

2
D3/2
2
D5/2
830
2
2
251
0
0
1/2
2
3/2
382
1/2
2
161
0
D5/2
2
37
D 5/2
2
0
0
–163
3/2
2
D5/2
Assignment
120 rotational transitions
81
2
–1
Ni Br A D5/2(～37cm )
58
J=37.5–36.5
Reduced mass ratio
L-type doubling
58Ni79Br(35％), 58Ni81Br(34％)
X23/2
, A2D5/2
anomaly in spectral pattern
L–type doubling
238895
(MHz)
238901
Fortrat Diagram of the NiBr radical
ν/J’≒2B
J'
60
50
2
X 3/2
2
A D5/2
60
40
50
40
6268
30
6300
n /2 J'
6269
(MHz)
6270
6400
large perturbation in X23/2 – simultaneous analysis needed
Deperturbed molecular constants
B
D
H
q
qD
ΔG
X23/2
A2D5/2
3176.958(60) 3184.881(60)
1.115(49)
1.613(49)
-302(32)
0.0239(10)
448.84(47)
10.4(16)
37cm-1(LIF, fixed)
MHz
kHz
mHz
mHz
mHz
J’
60
A2D5/2
X23/2
50
40
30
3120
ν/J’≒2B
(MHz)
●●
○○
perturbed (obs.)3230
deperturbed (calc.)
Summary
Features of Sputtering Method
Advantage
various metals
 various gasses
 inexpensive, safe to apply

wide possibility of compounds
Rather low temperature is sufficient
Disadvantage
low concentration compared with HT-cell
 high energy state difficult to observe
FeCl, CoF, AuO lowest spin state

mmW studies using the sputtering method
Sputtering Yield
No. of Sputtered Metal Atoms
Sputtering Yield =
No. of Rare Gas Ions
Ag
+
Ar+: more effective than He+
Higher sputtering yield
for atoms with more
d-electrons
Ar+
3
Yield at 600 eV

Under Ar bombardment
+
He bombardment
Au
Pd
Cu
2
Ni
Al
Co
Cr
Fe
1
Pt
Rh
Ru
Ge
Ir
Mo
Be
V
Si
Hf
Zr
Ti
Nb
U
Re Os
Ta
Th
W
He+
0
10
20
30
40 50
60
Atomic Number
70
80
90