152
S. Rashev and D.C. Moule
Table 8.4 Calculated vibrational states in S 0 H 2 CO, of other symmetries (A 2 , B 1 , B 2 ), using the
refined PES in this work (column 2). The experimentally measured frequencies [6] are displayed
in column 2, for comparison. Assignments and symmetries of the states are given in column 1
Assignment and symmetry
Calculated with the refined PES
Measured [6]
ν 4 (B 1 )
1167.26
1167.4
ν 6 (B 2 )
1249.89
1249.6
ν 4 + ν 6 (A 2 )
2422.74
2422.4
ν 3 + ν 4 (B 1 )
2666.80
2667.1
ν 3 + ν 1 (B 2 )
2719.47
2718.6
ν 5 (B 2 )
2843.61
2843.0
ν 2 + ν 4 (B 1 )
2905.22
2906.0
ν 2 + ν 6 (B 2 )
3001.12
3000.6
3ν 4 (B 1 )
3481.40
3480.7
2ν 4 + ν 6 (B 2 )
3585.60
3586.6
ν 4 + 2ν 6 (B 1 )
3676.26
3673.5
ν 3 + ν 4 + ν 6 (A 2 )
3889.41
3886.5
ν 1 + ν 4 (B 1 )
3941.99
3940.2
ν 3 + ν 4 + ν 6 (A 2 )
4164.99
4163.9
ν 2 + ν 3 + ν 4 (B 1 )
4396.10
4397.5
ν 2 + ν 3 + ν 6 (B 2 )
4467.04
4466.8
ν 2 + ν 5 (B 2 )
4572.78
4571.5
2ν 2 + ν 4 (B 1 )
4622.90
4624.3
2ν 2 + ν 6 (B 2 )
4736.46
4733.8
2ν 4 + ν 6 (A 2 )
4740.83
4741.9
ν 3 + 3ν 4 (B 1 )
4975.65
4977.1
ν 3 + 2ν 4 + ν 6 (B 2 )
5046.88
5043.7
above coordinates 1–4, respectively. As it is seen from the figures, all four fields
show very similar behavior up to quite high excitation levels, with only the ab initio
Yachmenev et al. field [24] showing marked deviation, for the CH stretch.
Using the obtained refined quartic PES in this work, we have also carried out a
calculation on the vibrational frequencies in HDCO. It was our purpose to find how
well does the PES, fitted to the vibrational frequencies of H 2 CO, perform for the
isotopomer HDCO. In Table 8.5 are displayed the results from our calculation of
all A (even number of ν 4 quanta) vibrational states in S 0 HDCO, in the range up
to E v = 5000 cm −1 . In this table, the results from the calculations with our newly
obtained refined PES, are compared to the results from our recent calculations [29],
using the original ab initio MLT PES [22], as well as to the set of experimentally
measured frequencies in the recent work of Ellsworth et al. [33]. It can be seen from
Table 8.5, that there is a marked improvement in the calculations with the refined
PES over the results obtained with the original MLT field, as regards the comparison
with experimental results [33]. However the improved frequencies are still too far
S. Rashev and D.C. Moule
Table 8.4 Calculated vibrational states in S 0 H 2 CO, of other symmetries (A 2 , B 1 , B 2 ), using the
refined PES in this work (column 2). The experimentally measured frequencies [6] are displayed
in column 2, for comparison. Assignments and symmetries of the states are given in column 1
Assignment and symmetry
Calculated with the refined PES
Measured [6]
ν 4 (B 1 )
1167.26
1167.4
ν 6 (B 2 )
1249.89
1249.6
ν 4 + ν 6 (A 2 )
2422.74
2422.4
ν 3 + ν 4 (B 1 )
2666.80
2667.1
ν 3 + ν 1 (B 2 )
2719.47
2718.6
ν 5 (B 2 )
2843.61
2843.0
ν 2 + ν 4 (B 1 )
2905.22
2906.0
ν 2 + ν 6 (B 2 )
3001.12
3000.6
3ν 4 (B 1 )
3481.40
3480.7
2ν 4 + ν 6 (B 2 )
3585.60
3586.6
ν 4 + 2ν 6 (B 1 )
3676.26
3673.5
ν 3 + ν 4 + ν 6 (A 2 )
3889.41
3886.5
ν 1 + ν 4 (B 1 )
3941.99
3940.2
ν 3 + ν 4 + ν 6 (A 2 )
4164.99
4163.9
ν 2 + ν 3 + ν 4 (B 1 )
4396.10
4397.5
ν 2 + ν 3 + ν 6 (B 2 )
4467.04
4466.8
ν 2 + ν 5 (B 2 )
4572.78
4571.5
2ν 2 + ν 4 (B 1 )
4622.90
4624.3
2ν 2 + ν 6 (B 2 )
4736.46
4733.8
2ν 4 + ν 6 (A 2 )
4740.83
4741.9
ν 3 + 3ν 4 (B 1 )
4975.65
4977.1
ν 3 + 2ν 4 + ν 6 (B 2 )
5046.88
5043.7
above coordinates 1–4, respectively. As it is seen from the figures, all four fields
show very similar behavior up to quite high excitation levels, with only the ab initio
Yachmenev et al. field [24] showing marked deviation, for the CH stretch.
Using the obtained refined quartic PES in this work, we have also carried out a
calculation on the vibrational frequencies in HDCO. It was our purpose to find how
well does the PES, fitted to the vibrational frequencies of H 2 CO, perform for the
isotopomer HDCO. In Table 8.5 are displayed the results from our calculation of
all A (even number of ν 4 quanta) vibrational states in S 0 HDCO, in the range up
to E v = 5000 cm −1 . In this table, the results from the calculations with our newly
obtained refined PES, are compared to the results from our recent calculations [29],
using the original ab initio MLT PES [22], as well as to the set of experimentally
measured frequencies in the recent work of Ellsworth et al. [33]. It can be seen from
Table 8.5, that there is a marked improvement in the calculations with the refined
PES over the results obtained with the original MLT field, as regards the comparison
with experimental results [33]. However the improved frequencies are still too far