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Absorption spectrum of gaseous terbium monofluoride
JOvBNALoP
494-495 (1978)
~o~U~SP~~OSCOPY~,
Absorption Spectrum of Gaseous Terbium Monofluoride The spectroscopic properties of the gaseous diatomic compounds of the transition metals are not well understood. Mass spectrometric studies of high-temperature gaseous equilibria have shown many of the rare earth compounds-especially the oxides and halides-to be stable, and some bands of HoF were analyzed a few years ago (1). Natural terbium is another of the rare earths which is isotopically simple and we have found that some regions of the absorption spectrum of gaseous TbF may be readily analyzed. Red degraded bands assigned to TbF were observed in absorption in the region 4600 to 6400 .&when mixtures of about 0.2 g of Tb with 0.4 g AlFz were heated to about 2000 EL Plates for rotational analysis were taken with a 3&m Jarred-Ash Ebert spectrograph. Vibrational analysis reveals at least five systems. Three systems with a common lower state have been analyzed. Wavelengths of prominent heads are given in Table I. Bands of the I&-.X and C-X systems have two strong branches, a head-forming R branch and a P branch. A weak Q branch, whose intensity decreases rapidly with increasing J, is also present. In the B-X 0-O band, the first Q line is clearly identified as Q(6). The atates X, B, and C all seem then to be
TABLE 1 Band Heads (A) and Band Origins (cm-r) of TbF system c-x
System
B-X
Bsnd
J., 8
V*’
5018.54
19916.70
O-I
5177.28
19305.60 f 2
Band
1,
I-O
Note i
A-X
those
-1
o-o
Vo’
LT
2-o
Systam
cm
4972.08
cm
f
2
-I
20633.39
f
2
20103.28
t
I
o-o
5108.15
19567.31
f
1
o-1
5272.12
18956.15
f
1
2-o
5449.04
18343‘50
*
7
1-O
5616.72
17795.66
f
8
Band
bandm
are
all
degraded
494
to
longer
wavelengths.
495
NOTES TABLE
II
Rotational Constants (cm-r) 107Dv
B” state
c
v=o
0.2415
r
3
1.5
i7
B
v=2
0.2380
* 2
2.0
f3
I
0.2400
f
I
2.0
*
0
0.24144
?
7
2.02
?: 4
0.2396
f
8
0.2393
f
8
A
v=2 I
X
Y=
I
I
0.25642
+ 7
1.72
t
0
0.25782
t
1.73
+ 5
TABLE
8
8
III
Molecular Constants state
T
e
we
xewe
Cn=6
19968
514.0
* 6
2.1
B3-6
19604
541.86
+ 6
2.9372
AR-7
17272
557.9
t
4
2.5
+
0
615.9
?
1
2.40
+ 6
XSl=6
Note:
Errors
quoted
values
of
and
r2/x2
re =
are were
three
times
calculated
103Ue
Be
=t?,
R
i:2 8
the with
0.24221
+ 8
1.55
0.25851
+ 8
1.385?
*
I
2.0246
f
3
6
1.9596
+ 3
I
standard p
deviations.
( ‘5qTblqF)
=
16.98112
The a . m. u
.
16.8575/pB.
ht = 6 states. Bands of the A-X system have strong R and Q branches with a very weak P branch. State A then appears to be an tl = 7 state. There are small irregularities in all the upper state levels. In addition, the B values for w = 1 and 2 of the A state are almost identical, so that one or both of these levels are perturbed. Rotational constants are given in Table II and derived molecular constants in Table III. As expected, the values of the ground state constants are very close to those for the ground state of HoF. ACKNOWLEDGMENT One of us (D.J.W.L.)
would like to thank the S.R.C. for the award of a studentship. REFERENCE
1. D. J. W.
ROBBINS
AND R.
F.
BARROW,
/.
Phys. B. 7, L234 (1974). D. J. W. R.
Physical Chmistry Laboratory Oxford University ox I 3Q2, England Re.ct&cdSc#ember 19,1977
F.
LIJMLEY
BARROW
494-495 (1978)
~o~U~SP~~OSCOPY~,
Absorption Spectrum of Gaseous Terbium Monofluoride The spectroscopic properties of the gaseous diatomic compounds of the transition metals are not well understood. Mass spectrometric studies of high-temperature gaseous equilibria have shown many of the rare earth compounds-especially the oxides and halides-to be stable, and some bands of HoF were analyzed a few years ago (1). Natural terbium is another of the rare earths which is isotopically simple and we have found that some regions of the absorption spectrum of gaseous TbF may be readily analyzed. Red degraded bands assigned to TbF were observed in absorption in the region 4600 to 6400 .&when mixtures of about 0.2 g of Tb with 0.4 g AlFz were heated to about 2000 EL Plates for rotational analysis were taken with a 3&m Jarred-Ash Ebert spectrograph. Vibrational analysis reveals at least five systems. Three systems with a common lower state have been analyzed. Wavelengths of prominent heads are given in Table I. Bands of the I&-.X and C-X systems have two strong branches, a head-forming R branch and a P branch. A weak Q branch, whose intensity decreases rapidly with increasing J, is also present. In the B-X 0-O band, the first Q line is clearly identified as Q(6). The atates X, B, and C all seem then to be
TABLE 1 Band Heads (A) and Band Origins (cm-r) of TbF system c-x
System
B-X
Bsnd
J., 8
V*’
5018.54
19916.70
O-I
5177.28
19305.60 f 2
Band
1,
I-O
Note i
A-X
those
-1
o-o
Vo’
LT
2-o
Systam
cm
4972.08
cm
f
2
-I
20633.39
f
2
20103.28
t
I
o-o
5108.15
19567.31
f
1
o-1
5272.12
18956.15
f
1
2-o
5449.04
18343‘50
*
7
1-O
5616.72
17795.66
f
8
Band
bandm
are
all
degraded
494
to
longer
wavelengths.
495
NOTES TABLE
II
Rotational Constants (cm-r) 107Dv
B” state
c
v=o
0.2415
r
3
1.5
i7
B
v=2
0.2380
* 2
2.0
f3
I
0.2400
f
I
2.0
*
0
0.24144
?
7
2.02
?: 4
0.2396
f
8
0.2393
f
8
A
v=2 I
X
Y=
I
I
0.25642
+ 7
1.72
t
0
0.25782
t
1.73
+ 5
TABLE
8
8
III
Molecular Constants state
T
e
we
xewe
Cn=6
19968
514.0
* 6
2.1
B3-6
19604
541.86
+ 6
2.9372
AR-7
17272
557.9
t
4
2.5
+
0
615.9
?
1
2.40
+ 6
XSl=6
Note:
Errors
quoted
values
of
and
r2/x2
re =
are were
three
times
calculated
103Ue
Be
=t?,
R
i:2 8
the with
0.24221
+ 8
1.55
0.25851
+ 8
1.385?
*
I
2.0246
f
3
6
1.9596
+ 3
I
standard p
deviations.
( ‘5qTblqF)
=
16.98112
The a . m. u
.
16.8575/pB.
ht = 6 states. Bands of the A-X system have strong R and Q branches with a very weak P branch. State A then appears to be an tl = 7 state. There are small irregularities in all the upper state levels. In addition, the B values for w = 1 and 2 of the A state are almost identical, so that one or both of these levels are perturbed. Rotational constants are given in Table II and derived molecular constants in Table III. As expected, the values of the ground state constants are very close to those for the ground state of HoF. ACKNOWLEDGMENT One of us (D.J.W.L.)
would like to thank the S.R.C. for the award of a studentship. REFERENCE
1. D. J. W.
ROBBINS
AND R.
F.
BARROW,
/.
Phys. B. 7, L234 (1974). D. J. W. R.
Physical Chmistry Laboratory Oxford University ox I 3Q2, England Re.ct&cdSc#ember 19,1977
F.
LIJMLEY
BARROW