The infrared absorption spectrum of C2H2 has been studied in the region from 2500 to 4150 cm−1. Nineteen bands were observed, of which 11 were sufficiently intense and well resolved to permit rotational analysis. Five bands involving the ground vibrational state were analyzed giving the rotational constants B0=1.17654±0.00004 and D0=1.51±0.03×10−6 cm−1. The l-doubling constants for the degenerate modes were determined to be q4=5.27, q5=4.63×10−3 cm−1. The rotational constants determined for the various observed states clearly show that additional data will be needed and due account taken of resonances to obtain a satisfactory set of rotational constants. The use of difference bands involving the v4=1-level permits the determination of the vibrational frequency of that level to be 612.88 cm−1.
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Calculated frequencies in vacuum wave numbers in three ∑−∑ bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
3ν41+ν51 Band center 2560.59
ν3 Band center 3281.92
ν2+ν41+ν51 Band center 3294.87
J
R branch
P branch
R branch
P branch
R branch
P branch
0
2562.95
3284.27
(0.25)
3297.21
(0.18)
1
65.34
(0.32)
2558.23
(0.26)
86.60
(0.59)
3279.57
(0.57)
99.55
(0.53)
3292.52
(0.50)
2
67.74
(0.77)
55.90
(0.93)
88.93
(0.92)
77.21
(0.22)
3301.88
(0.87)
90.16
(0.15)
3
70.16
(0.18)
53.57
(0.60)
91.25
(0.24)
74.84
(0.85)
04.19
(0.18)
87.78
(0.78)
4
72.59
(0.60)
51.27
(0.28)
93.56
(0.55)
72.46
(0.45)
06.50
(0.51)
85.40
(0.45)
5
75.04
(0.05)
48.98
(0.99)
95.86
(0.84)
70.07
(0.07)
08.80
(0.76)
83.02
(0.00)
6
77.50
(0.51)
46.71
(0.73)
98.15
(0.13)
67.68
(0.67)
11.09
(0.09)
80.62
(0.60)
7
80.00
(0.98)
44.46
(0.45)
3300.44
(0.44)
65.28
(0.26)
13.37
(0.36)
78.21
(0.20)
8
82.51
(0.50)
42.22
(0.21)
02.71
(0.72)
62.86
(0.86)
15.64
(0.64)
75.80
(0.78)
9
85.04
(0.04)
40.00
(0.98)
04.98
(0.98)
60.44
(0.44)
17.89
(0.88)
73.37
(0.35)
10
87.60
(0.58)
37.81
(0.80)
07.23
(0.25)
58.01
(0.02)
20.14
(0.15)
70.94
(0.93)
11
90.18
(0.17)
35.64
(0.62)
09.48
(0.48)
55.58
(0.57)
22.38
(0.40)
68.49
(0.48)
12
92.79
(0.78)
33.49
(0.48)
11.71
(0.73)
53.13
(0.12)
24.60
(0.61)
66.04
(0.05)
13
95.41
(0.41)
31.37
(0.36)
14.94
50.67
(0.67)
26.82
(0.82)
63.58
(0.58)
14
98.08
(0.09)
29.28
(0.27)
16.16
(0.17)
48.21
(0.21)
29.02
(0.06)
61.10
(0.12)
15
2600.78
(0.80)
27.21
(0.21)
18.36
(0.36)
45.74
31.21
(0.21)
58.62
(0.63)
16
03.50
(0.52)
25.18
(0.19)
20.55
(0.55)
43.25
(0.22)
33.39
(0.42)
56.12
(0.12)
17
06.26
(0.27)
23.17
(0.18)
22.74
(0.74)
40.76
(0.77)
35.55
(0.56)
53.61
(0.62)
18
09.07
(0.06)
21.20
(0.20)
24.90
(0.92)
38.26
(0.30)
37.70
(0.69)
51.09
(0.10)
19
11.91
(0.87)
19.28
(0.28)
27.07
(0.06)
35.75
(0.76)
39.83
(0.80)
48.56
(0.58)
20
17.39
(0.38)
29.21
(0.21)
33.22
(0.25)
41.95
(0.96)
46.02
(0.03)
21
31.35
(0.34)
30.70
(0.70)
44.06
(0.06)
43.46
(0.47)
22
33.47
(0.42)
28.15
(0.15)
46.15
(0.15)
41.89
23
35.58
(0.56)
25.60
(0.61)
48.22
(0.22)
38.31
(0.30)
24
37.68
(0.69)
23.03
(0.04)
50.27
(0.25)
35.71
25
39.76
(0.74)
20.46
(0.48)
52.31
(0.30)
33.10
(0.10)
26
41.82
(0.83)
17.87
(0.88)
54.33
(0.31)
30.47
(0.44)
27
43.87
(0.90)
15.26
(0.26)
56.32
(0.33)
27.81
(0.80)
28
45.92
(0.91)
12.66
(0.65)
58.31
(0.29)
25.16
(0.16)
29
47.94
(0.94)
10.03
(0.03)
60.26
(0.26)
22.48
(0.48)
30
49.94
(0.94)
07.40
(0.39)
62.20
(0.22)
19.78
(0.78)
31
51.94
(0.91)
04.74
(0.74)
64.11
(0.16)
17.07
(0.07)
32
53.91
(0.90)
02.08
(0.07)
66.00
(0.03)
14.33
(0.29)
33
55.87
(0.86)
3199.40
(0.41)
67.87
(0.93)
11.58
(0.62)
34
57.80
(0.83)
96.71
(0.70)
35
59.72
(0.76)
94.00
(0.03)
Table II
Calculated frequencies in vacuum wave numbers in two π−∑ bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
J
R branch
ν2+ν51 Band center 2701.92 P branch
Q branch
R branch
ν1+ν51 Band center 4091.20 P branch
Q branch
0
2704.26
(0.27)
4093.54
(0.50)
1
06.59
(0.59)
95.86
(0.85)
2
08.90
(0.91)
2697.20
(0.15)
98.18
(0.18)
4086.48
(0.48)
3
11.20
(0.20)
94.82
(0.84)
4100.47
(0.48)
84.10
(0.11)
4
13.49
(0.49)
92.43
02.76
(0.78)
81.70
(0.72)
5
15.77
(0.77)
90.03
(0.02)
05.02
(0.03)
79.30
(0.32)
6
18.03
(0.05)
87.61
(0.63)
07.28
(0.25)
76.87
(0.88)
7
20.28
(0.29)
85.18
(0.19)
09.52
(0.54)
74.44
(0.43)
8
22.52
(0.51)
82.74
11.74
(0.73)
71.99
(0.00)
9
24.74
(0.71)
80.29
(0.26)
13.95
(0.97)
69.52
(0.54)
10
26.95
(0.95)
77.82
(0.74)
16.15
(0.15)
67.05
(0.08)
11
29.15
(0.14)
75.34
(0.35)
18.33
(0.33)
64.55
(0.56)
12
31.33
(0.33)
72.85
(0.84)
20.50
(0.49)
62.05
(0.04)
13
33.50
(0.52)
70.35
(0.34)
2701.60
(0.60)
22.66
(0.64)
59.53
(0.53)
14
35.66
(0.67)
67.83
(0.85)
01.55
(0.55)
24.79
(0.76)
57.00
(0.96)
15
37.80
(0.79)
65.30
(0.29)
01.50
(0.49)
26.92
(0.91)
54.45
(0.47)
16
39.93
(0.92)
62.76
(0.76)
01.44
(0.44)
29.03
(0.03)
51.89
(0.91)
17
42.05
(0.04)
60.21
(0.19)
01.38
(0.38)
31.12
(0.12)
49.32
(0.32)
18
44.15
(0.14)
57.64
(0.62)
01.32
(0.32)
33.20
(0.21)
46.74
(0.72)
19
46.23
(0.23)
55.06
(0.05)
01.25
(0.25)
35.27
(0.27)
44.14
(0.15)
4090.32
(0.30)
20
48.30
(0.31)
52.47
(0.43)
01.18
(0.17)
37.32
(0.31)
41.52
(0.50)
90.22
(0.21)
21
50.36
(0.38)
49.86
(0.86)
01.10
(0.10)
39.36
(0.34)
38.90
(0.90)
90.13
(0.11)
22
52.41
47.24
(0.23)
01.02
(0.03)
41.38
(0.34)
36.26
(0.25)
90.02
(0.01)
23
54.44
(0.44)
44.61
(0.60)
00.94
(0.95)
43.39
(0.35)
33.61
(0.61)
89.92
(0.93)
24
56.45
(0.47)
41.97
(0.95)
00.86
45.38
(0.36)
30.94
(0.97)
89.81
(0.82)
25
58.45
(0.48)
39.31
(0.25)
00.77
(0.77)
47.35
(0.34)
28.26
(0.27)
89.70
(0.70)
26
36.64
(0.62)
00.67
(0.68)
49.33
(0.34)
25.57
89.57
(0.59)
27
33.95
(0.99)
00.58
(0.58)
51.25
(0.22)
22.86
(0.84)
89.45
(0.47)
28
00.48
53.19
(0.22)
20.16
(0.18)
89.32
(0.33)
29
00.37
(0.36)
55.11
(0.11)
17.42
(0.44)
89.19
(0.20)
30
57.01
(0.02)
14.67
(0.71)
89.05
(0.06)
31
58.90
(0.95)
11.92
(0.91)
88.91
(0.92)
32
09.15
(0.12)
88.76
(0.76)
33
88.61
(0.60)
34
88.45
(0.44)
35
88.29
(0.26)
Table III
Calculated frequencies in vacuum wave numbers in three ∑−π bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
ν3−ν41 Band center 2670.23
ν2+ν41+ν51−ν41 Band center 2683.18
ν1−ν51 Band center 2643.71
R branch
P branch
Q branch
R branch
P branch
Q branch
R branch
P branch
Q branch
1
2674.91
(0.92)
2687.86
(0.85)
2648.38
(0.41)
2641.38
2
77.24
2665.52
(0.53)
90.19
(0.17)
2678.47
(0.47)
50.70
(0.68)
39.00
(0.98)
3
79.57
(0.52)
63.16
(0.15)
92.52
76.11
(0.09)
53.00
(0.98)
36.62
(0.62)
4
81.89
(0.86)
60.79
(0.78)
94.84
(0.84)
73.74
(0.73)
55.28
(0.27)
34.23
(0.22)
5
84.21
(0.20)
58.42
(0.40)
97.15
(0.15)
71.36
(0.35)
57.55
(0.56)
31.82
(0.83)
2643.37
(0.37)
6
86.52
(0.52)
56.04
(0.04)
2669.91
(0.91)
99.45
(0.44)
68.98
(0.95)
59.81
(0.81)
29.40
(0.41)
43.23
(0.23)
7
88.82
(0.83)
53.65
(0.66)
69.79
(0.79)
2701.75
66.59
(0.57)
2682.58
(0.57)
62.06
(0.06)
26.97
(0.96)
43.07
(0.07)
8
91.11
(0.14
51.26
(0.27)
69.66
(0.65)
04.04
(0.04)
64.20
82.43
(0.42)
64.29
(0.28)
24.53
(0.53)
42.89
(0.90)
9
93.40
(0.42)
48.87
(0.86)
69.51
(0.50)
06.32
(0.33)
61.79
(0.80)
82.26
(0.26)
66.51
(0.53)
22.07
(0.07)
42.69
(0.68)
10
95.68
(0.69)
46.46
(0.48)
69.35
(0.33)
08.60
(0.59)
59.38
(0.40)
82.07
(0.06)
68.71
(0.71)
19.60
(0.59)
42.46
(0.47)
11
97.95
(0.98)
44.05
(0.06)
69.16
(0.16)
10.86
(0.87)
56.97
(0.98)
81.86
(0.86)
70.90
(0.89)
17.11
(0.12)
42.22
(0.22)
12
2700.23
(0.22)
41.64
(0.66)
68.96
(0.95)
13.12
(0.13)
54.55
(0.56)
81.63
(0.64)
73.08
(0.06)
14.63
(0.61)
41.94
(0.95)
13
02.48
(0.49)
39.22
(0.25)
68.75
(0.71)
15.37
(0.38)
52.12
(0.13)
81.38
(0.38)
75.24
(0.25)
12.11
(0.11)
41.65
(0.66)
14
04.73
(0.75)
36.80
(0.81)
68.51
(0.51)
17.61
(0.62)
49.68
(0.69)
81.12
(0.12)
77.39
(0.39)
09.58
(0.59)
41.33
(0.34)
15
06.98
(0.99)
34.36
(0.36)
68.26
(0.26)
19.84
(0.84)
47.23
(0.23)
80.83
(0.81)
79.52
(0.52)
07.05
(0.05)
40.99
(0.99)
16
09.22
(0.23)
31.91
(0.92)
67.99
(0.98)
22.07
(0.06)
44.78
(0.80)
80.52
(0.55)
81.64
(0.64)
04.50
(0.51)
40.63
(0.62)
17
11.44
(0.46)
29.47
(0.47)
67.70
(0.72)
24.28
(0.28)
42.32
(0.32)
80.18
83.75
(0.74)
01.94
(0.94)
40.25
(0.24)
18
13.66
(0.69)
27.01
(0.96)
67.40
(0.42)
26.46
(0.48)
39.84
(0.84)
79.86
(0.88)
85.84
(0.86)
2599.36
(0.36)
39.84
(0.84)
19
15.87
(0.87)
67.07
(0.08)
28.65
(0.65)
37.36
(0.37)
79.50
(0.52)
87.92
(0.92)
96.78
(0.78)
39.41
(0.40)
20
18.07
(0.05)
66.73
(0.75)
30.82
(0.82)
34.87
(0.87)
79.12
(0.13)
89.98
(0.02)
94.18
(0.18)
38.96
(0.98)
21
20.26
(0.29)
66.37
(0.38)
32.98
(0.97)
32.37
(0.39)
78.72
(0.70)
92.03
(0.05)
91.57
(0.58)
38.48
(0.49)
22
22.48
65.99
(0.99)
35.13
(0.14)
29.86
(0.86)
78.28
(0.26)
94.07
(0.08)
88.95
(0.95)
37.98
(0.99)
23
24.61
(0.64)
65.59
(0.57)
37.26
(0.26)
27.34
(0.34)
96.09
(0.11)
86.31
(0.32)
37.46
(0.40)
24
26.78
(0.79)
65.17
(0.18)
39.38
(0.37)
24.80
(0.81)
98.10
(0.13)
83.66
(0.68)
36.92
(0.91)
25
28.93
(0.94)
64.75
(0.74)
41.48
(0.48)
22.25
(0.27)
2700.09
(0.03)
81.00
(0.01)
36.38
(0.36)
26
64.27
(0.28)
43.57
(0.57)
19.70
02.07
(0.96)
78.33
(0.35)
35.77
(0.78)
27
63.79
(0.79)
45.64
(0.65)
17.12
(0.12)
04.03
(0.04)
75.64
(0.63)
35.16
(0.16)
28
63.29
(0.29)
47.69
(0.68)
14.54
(0.61)
05.98
(0.04)
72.94
(0.97)
34.52
(0.52)
29
49.73
(0.73)
11.94
(0.96)
07.92
70.24
(0.18)
33.87
(0.91)
30
09.32
(0.36)
09.84
67.51
(0.52)
Table IV
Calculated frequencies in vacuum wave numbers in two π−π bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
ν2+2ν40+ν51−ν41 Band center 3285.58
ν1+ν51−ν41 Band center 3479.47
J
R branch
P branch
R branch
P branch
1
3484.14
(0.14)
2
86.46
(0.48)
3474.74
(0.74)
3
88.67
72.36
(0.34)
4
91.07
(0.09)
69.98
(0.97)
5
93.35
(0.37)
67.47
6
3271.28
(0.20)
3271.32
(0.24)
95.63
(0.66)
3465.12
(0.10)
3465.17
(0.14)
7
68.86
(0.79)
68.91
(0.85)
97.89
(0.89)
62.68
62.78
8
66.43
(0.34)
66.48
(0.41)
3500.14
(0.18)
60.23
(0.22)
60.35
(0.34)
9
64.00
(0.92)
64.06
(0.99)
02.37
(0.39)
57.79
(0.77)
57.91
(0.90)
10
3310.75
(0.71)
3310.91
(0.89)
61.56
(0.50)
61.62
(0.57)
04.60
(0.58)
55.32
(0.31)
55.46
(0.45)
11
12.98
(0.95)
13.16
(0.09)
59.10
(0.07)
59.16
(0.12)
06.81
(0.80)
52.84
(0.84)
53.00
(0.00)
12
15.18
(0.18)
15.40
(0.36)
56.64
(0.60)
56.70
(0.66)
09.01
(0.02)
50.33
(0.34)
50.52
(0.53)
13
17.38
(0.46)
17.62
(0.61)
54.17
(0.17)
54.23
(0.25)
11.20
(0.18)
47.84
(0.86)
48.04
(0.05)
14
19.65
(0.64)
19.91
(0.81)
51.66
(0.66)
51.74
(0.73)
13.37
(0.38)
45.32
(0.30)
45.55
(0.55)
15
21.84
(0.76)
22.12
(0.03)
49.19
(0.17)
49.25
(0.23)
15.52
(0.51)
42.79
(0.79)
43.04
(0.05)
16
23.92
(0.95)
24.22
(0.24)
46.69
(0.68)
46.75
(0.73)
17.68
(0.67)
40.25
(0.26)
40.53
(0.53)
17
26.07
(0.08)
26.41
(0.43)
44.17
(0.16)
44.23
(0.21)
19.82
(0.80)
37.70
(0.69)
38.00
(0.00)
18
28.21
(0.23)
28.57
(0.59)
41.65
(0.64)
41.70
(0.68)
21.94
(0.94)
35.14
(0.14)
35.46
(0.46)
19
30.35
(0.37)
30.72
(0.80)
39.13
(0.14)
39.18
(0.16)
24.06
(0.11)
32.54
(0.56)
32.91
(0.90)
20
32.46
(0.46)
32.88
(0.90)
3236.60
(0.62)
26.16
(0.14)
29.97
(0.97)
30.35
(0.34)
21
34.56
(0.59)
35.00
(0.05)
34.05
(0.07)
28.24
(0.22)
27.37
(0.38)
27.77
(0.78)
22
36.65
(0.70)
37.13
(0.18)
31.48
(0.51)
30.31
(0.31)
24.75
(0.76)
25.17
(0.20)
23
38.74
(0.73)
39.24
(0.26)
28.91
(0.93)
32.37
(0.37)
22.12
(0.14)
22.60
(0.60)
24
40.80
(0.82)
41.34
(0.33)
26.32
(0.34)
34.42
(0.41)
25
42.84
(0.83)
43.42
(0.44)
23.72
(0.72)
26
44.88
(0.88)
45.49
(0.48)
21.11
(0.10)
27
46.91
(0.84)
47.55
(0.54)
18.49
(0.49)
28
48.92
(0.87)
49.60
(0.47)
15.86
(0.86)
29
50.91
(0.84)
51.63
(0.56)
13.22
30
52.89
(0.80)
53.65
(0.54)
10.56
(0.50)
31
54.86
(0.74)
55.66
(0.52)
07.89
(0.92)
32
56.41
(0.65)
57.62
(0.44)
33
58.74
(0.57)
59.62
(0.41)
Table V
Observed band centers, band origins, and changes in rotational constants of some bands of C2H2. All numerical quantities are expressed in vacuum-wave numbers.
Rotational constants calculated using average values of the doublet frequencies.
Table VI
Calculated and observed values of Δ2F for the ground state of C2H2 as obtained from several bands. For observed values only the fractional part is given.
J
Calc
ν1+ν51
ν2+ν41+ν51
ν3
ν2+ν51
3ν41+ν51
1
7.059
0.02
0.03
0.03
2
11.765
0.74
0.74
0.75
0.72
3
16.471
0.46
0.42
0.47
0.49
4
21.177
0.16
0.18
0.17
0.18
0.19
5
25.882
0.90
0.91
0.88
0.86
0.87
6
30.587
0.60
0.56
0.58
0.60
0.60
7
35.291
0.25
0.31
0.27
0.30
8
39.995
0.00
0.01
0.00
0.03
0.00
9
44.699
0.65
0.71
0.70
0.70
10
49.401
0.41
0.40
0.41
0.36
0.42
11
54.103
0.11
0.10
0.13
0.11
0.11
12
58.803
0.80
0.82
0.81
0.80
0.81
13
63.503
0.53
0.49
0.52
0.48
0.51
14
68.202
0.17
0.19
0.23
0.20
15
72.900
0.85
0.95
0.91
0.90
16
77.598
0.59
0.59
0.60
0.62
17
82.293
0.31
0.32
0.25
0.30
0.32
18
86.987
0.97
0.98
0.98
0.99
0.99
19
91.680
0.71
0.66
0.67
0.71
0.68
20
96.372
0.37
0.33
0.36
0.37
21
101.062
0.06
0.06
0.08
22
105.751
0.73
0.73
0.78
23
110.438
0.37
0.39
0.38
24
115.123
0.08
0.12
0.08
25
119.806
0.81
0.81
0.85
26
124.487
0.50
0.50
0.48
0.49
27
129.167
0.16
0.15
0.18
28
133.845
0.85
0.87
29
138.521
0.51
0.51
0.52
30
143.194
0.20
0.19
0.20
31
147.865
0.90
0.93
0.87
32
152.534
0.54
0.50
Table VII
Values of Bv and changes in B from the ground state for several vibrational states in C2H2. For π states the average value of the two levels is given.
Calculated frequency of the ν4 fundamental frequency.
(ν1+ν51)−(ν1+ν51−ν41)=612.90
(ν3)−(ν3−ν41)=612.87
(ν2+ν41+ν51)−(ν2+ν41+ν51−ν41)=612.87
Average=612.88 cm−1
Tables (8)
Table I
Calculated frequencies in vacuum wave numbers in three ∑−∑ bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
3ν41+ν51 Band center 2560.59
ν3 Band center 3281.92
ν2+ν41+ν51 Band center 3294.87
J
R branch
P branch
R branch
P branch
R branch
P branch
0
2562.95
3284.27
(0.25)
3297.21
(0.18)
1
65.34
(0.32)
2558.23
(0.26)
86.60
(0.59)
3279.57
(0.57)
99.55
(0.53)
3292.52
(0.50)
2
67.74
(0.77)
55.90
(0.93)
88.93
(0.92)
77.21
(0.22)
3301.88
(0.87)
90.16
(0.15)
3
70.16
(0.18)
53.57
(0.60)
91.25
(0.24)
74.84
(0.85)
04.19
(0.18)
87.78
(0.78)
4
72.59
(0.60)
51.27
(0.28)
93.56
(0.55)
72.46
(0.45)
06.50
(0.51)
85.40
(0.45)
5
75.04
(0.05)
48.98
(0.99)
95.86
(0.84)
70.07
(0.07)
08.80
(0.76)
83.02
(0.00)
6
77.50
(0.51)
46.71
(0.73)
98.15
(0.13)
67.68
(0.67)
11.09
(0.09)
80.62
(0.60)
7
80.00
(0.98)
44.46
(0.45)
3300.44
(0.44)
65.28
(0.26)
13.37
(0.36)
78.21
(0.20)
8
82.51
(0.50)
42.22
(0.21)
02.71
(0.72)
62.86
(0.86)
15.64
(0.64)
75.80
(0.78)
9
85.04
(0.04)
40.00
(0.98)
04.98
(0.98)
60.44
(0.44)
17.89
(0.88)
73.37
(0.35)
10
87.60
(0.58)
37.81
(0.80)
07.23
(0.25)
58.01
(0.02)
20.14
(0.15)
70.94
(0.93)
11
90.18
(0.17)
35.64
(0.62)
09.48
(0.48)
55.58
(0.57)
22.38
(0.40)
68.49
(0.48)
12
92.79
(0.78)
33.49
(0.48)
11.71
(0.73)
53.13
(0.12)
24.60
(0.61)
66.04
(0.05)
13
95.41
(0.41)
31.37
(0.36)
14.94
50.67
(0.67)
26.82
(0.82)
63.58
(0.58)
14
98.08
(0.09)
29.28
(0.27)
16.16
(0.17)
48.21
(0.21)
29.02
(0.06)
61.10
(0.12)
15
2600.78
(0.80)
27.21
(0.21)
18.36
(0.36)
45.74
31.21
(0.21)
58.62
(0.63)
16
03.50
(0.52)
25.18
(0.19)
20.55
(0.55)
43.25
(0.22)
33.39
(0.42)
56.12
(0.12)
17
06.26
(0.27)
23.17
(0.18)
22.74
(0.74)
40.76
(0.77)
35.55
(0.56)
53.61
(0.62)
18
09.07
(0.06)
21.20
(0.20)
24.90
(0.92)
38.26
(0.30)
37.70
(0.69)
51.09
(0.10)
19
11.91
(0.87)
19.28
(0.28)
27.07
(0.06)
35.75
(0.76)
39.83
(0.80)
48.56
(0.58)
20
17.39
(0.38)
29.21
(0.21)
33.22
(0.25)
41.95
(0.96)
46.02
(0.03)
21
31.35
(0.34)
30.70
(0.70)
44.06
(0.06)
43.46
(0.47)
22
33.47
(0.42)
28.15
(0.15)
46.15
(0.15)
41.89
23
35.58
(0.56)
25.60
(0.61)
48.22
(0.22)
38.31
(0.30)
24
37.68
(0.69)
23.03
(0.04)
50.27
(0.25)
35.71
25
39.76
(0.74)
20.46
(0.48)
52.31
(0.30)
33.10
(0.10)
26
41.82
(0.83)
17.87
(0.88)
54.33
(0.31)
30.47
(0.44)
27
43.87
(0.90)
15.26
(0.26)
56.32
(0.33)
27.81
(0.80)
28
45.92
(0.91)
12.66
(0.65)
58.31
(0.29)
25.16
(0.16)
29
47.94
(0.94)
10.03
(0.03)
60.26
(0.26)
22.48
(0.48)
30
49.94
(0.94)
07.40
(0.39)
62.20
(0.22)
19.78
(0.78)
31
51.94
(0.91)
04.74
(0.74)
64.11
(0.16)
17.07
(0.07)
32
53.91
(0.90)
02.08
(0.07)
66.00
(0.03)
14.33
(0.29)
33
55.87
(0.86)
3199.40
(0.41)
67.87
(0.93)
11.58
(0.62)
34
57.80
(0.83)
96.71
(0.70)
35
59.72
(0.76)
94.00
(0.03)
Table II
Calculated frequencies in vacuum wave numbers in two π−∑ bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
J
R branch
ν2+ν51 Band center 2701.92 P branch
Q branch
R branch
ν1+ν51 Band center 4091.20 P branch
Q branch
0
2704.26
(0.27)
4093.54
(0.50)
1
06.59
(0.59)
95.86
(0.85)
2
08.90
(0.91)
2697.20
(0.15)
98.18
(0.18)
4086.48
(0.48)
3
11.20
(0.20)
94.82
(0.84)
4100.47
(0.48)
84.10
(0.11)
4
13.49
(0.49)
92.43
02.76
(0.78)
81.70
(0.72)
5
15.77
(0.77)
90.03
(0.02)
05.02
(0.03)
79.30
(0.32)
6
18.03
(0.05)
87.61
(0.63)
07.28
(0.25)
76.87
(0.88)
7
20.28
(0.29)
85.18
(0.19)
09.52
(0.54)
74.44
(0.43)
8
22.52
(0.51)
82.74
11.74
(0.73)
71.99
(0.00)
9
24.74
(0.71)
80.29
(0.26)
13.95
(0.97)
69.52
(0.54)
10
26.95
(0.95)
77.82
(0.74)
16.15
(0.15)
67.05
(0.08)
11
29.15
(0.14)
75.34
(0.35)
18.33
(0.33)
64.55
(0.56)
12
31.33
(0.33)
72.85
(0.84)
20.50
(0.49)
62.05
(0.04)
13
33.50
(0.52)
70.35
(0.34)
2701.60
(0.60)
22.66
(0.64)
59.53
(0.53)
14
35.66
(0.67)
67.83
(0.85)
01.55
(0.55)
24.79
(0.76)
57.00
(0.96)
15
37.80
(0.79)
65.30
(0.29)
01.50
(0.49)
26.92
(0.91)
54.45
(0.47)
16
39.93
(0.92)
62.76
(0.76)
01.44
(0.44)
29.03
(0.03)
51.89
(0.91)
17
42.05
(0.04)
60.21
(0.19)
01.38
(0.38)
31.12
(0.12)
49.32
(0.32)
18
44.15
(0.14)
57.64
(0.62)
01.32
(0.32)
33.20
(0.21)
46.74
(0.72)
19
46.23
(0.23)
55.06
(0.05)
01.25
(0.25)
35.27
(0.27)
44.14
(0.15)
4090.32
(0.30)
20
48.30
(0.31)
52.47
(0.43)
01.18
(0.17)
37.32
(0.31)
41.52
(0.50)
90.22
(0.21)
21
50.36
(0.38)
49.86
(0.86)
01.10
(0.10)
39.36
(0.34)
38.90
(0.90)
90.13
(0.11)
22
52.41
47.24
(0.23)
01.02
(0.03)
41.38
(0.34)
36.26
(0.25)
90.02
(0.01)
23
54.44
(0.44)
44.61
(0.60)
00.94
(0.95)
43.39
(0.35)
33.61
(0.61)
89.92
(0.93)
24
56.45
(0.47)
41.97
(0.95)
00.86
45.38
(0.36)
30.94
(0.97)
89.81
(0.82)
25
58.45
(0.48)
39.31
(0.25)
00.77
(0.77)
47.35
(0.34)
28.26
(0.27)
89.70
(0.70)
26
36.64
(0.62)
00.67
(0.68)
49.33
(0.34)
25.57
89.57
(0.59)
27
33.95
(0.99)
00.58
(0.58)
51.25
(0.22)
22.86
(0.84)
89.45
(0.47)
28
00.48
53.19
(0.22)
20.16
(0.18)
89.32
(0.33)
29
00.37
(0.36)
55.11
(0.11)
17.42
(0.44)
89.19
(0.20)
30
57.01
(0.02)
14.67
(0.71)
89.05
(0.06)
31
58.90
(0.95)
11.92
(0.91)
88.91
(0.92)
32
09.15
(0.12)
88.76
(0.76)
33
88.61
(0.60)
34
88.45
(0.44)
35
88.29
(0.26)
Table III
Calculated frequencies in vacuum wave numbers in three ∑−π bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
ν3−ν41 Band center 2670.23
ν2+ν41+ν51−ν41 Band center 2683.18
ν1−ν51 Band center 2643.71
R branch
P branch
Q branch
R branch
P branch
Q branch
R branch
P branch
Q branch
1
2674.91
(0.92)
2687.86
(0.85)
2648.38
(0.41)
2641.38
2
77.24
2665.52
(0.53)
90.19
(0.17)
2678.47
(0.47)
50.70
(0.68)
39.00
(0.98)
3
79.57
(0.52)
63.16
(0.15)
92.52
76.11
(0.09)
53.00
(0.98)
36.62
(0.62)
4
81.89
(0.86)
60.79
(0.78)
94.84
(0.84)
73.74
(0.73)
55.28
(0.27)
34.23
(0.22)
5
84.21
(0.20)
58.42
(0.40)
97.15
(0.15)
71.36
(0.35)
57.55
(0.56)
31.82
(0.83)
2643.37
(0.37)
6
86.52
(0.52)
56.04
(0.04)
2669.91
(0.91)
99.45
(0.44)
68.98
(0.95)
59.81
(0.81)
29.40
(0.41)
43.23
(0.23)
7
88.82
(0.83)
53.65
(0.66)
69.79
(0.79)
2701.75
66.59
(0.57)
2682.58
(0.57)
62.06
(0.06)
26.97
(0.96)
43.07
(0.07)
8
91.11
(0.14
51.26
(0.27)
69.66
(0.65)
04.04
(0.04)
64.20
82.43
(0.42)
64.29
(0.28)
24.53
(0.53)
42.89
(0.90)
9
93.40
(0.42)
48.87
(0.86)
69.51
(0.50)
06.32
(0.33)
61.79
(0.80)
82.26
(0.26)
66.51
(0.53)
22.07
(0.07)
42.69
(0.68)
10
95.68
(0.69)
46.46
(0.48)
69.35
(0.33)
08.60
(0.59)
59.38
(0.40)
82.07
(0.06)
68.71
(0.71)
19.60
(0.59)
42.46
(0.47)
11
97.95
(0.98)
44.05
(0.06)
69.16
(0.16)
10.86
(0.87)
56.97
(0.98)
81.86
(0.86)
70.90
(0.89)
17.11
(0.12)
42.22
(0.22)
12
2700.23
(0.22)
41.64
(0.66)
68.96
(0.95)
13.12
(0.13)
54.55
(0.56)
81.63
(0.64)
73.08
(0.06)
14.63
(0.61)
41.94
(0.95)
13
02.48
(0.49)
39.22
(0.25)
68.75
(0.71)
15.37
(0.38)
52.12
(0.13)
81.38
(0.38)
75.24
(0.25)
12.11
(0.11)
41.65
(0.66)
14
04.73
(0.75)
36.80
(0.81)
68.51
(0.51)
17.61
(0.62)
49.68
(0.69)
81.12
(0.12)
77.39
(0.39)
09.58
(0.59)
41.33
(0.34)
15
06.98
(0.99)
34.36
(0.36)
68.26
(0.26)
19.84
(0.84)
47.23
(0.23)
80.83
(0.81)
79.52
(0.52)
07.05
(0.05)
40.99
(0.99)
16
09.22
(0.23)
31.91
(0.92)
67.99
(0.98)
22.07
(0.06)
44.78
(0.80)
80.52
(0.55)
81.64
(0.64)
04.50
(0.51)
40.63
(0.62)
17
11.44
(0.46)
29.47
(0.47)
67.70
(0.72)
24.28
(0.28)
42.32
(0.32)
80.18
83.75
(0.74)
01.94
(0.94)
40.25
(0.24)
18
13.66
(0.69)
27.01
(0.96)
67.40
(0.42)
26.46
(0.48)
39.84
(0.84)
79.86
(0.88)
85.84
(0.86)
2599.36
(0.36)
39.84
(0.84)
19
15.87
(0.87)
67.07
(0.08)
28.65
(0.65)
37.36
(0.37)
79.50
(0.52)
87.92
(0.92)
96.78
(0.78)
39.41
(0.40)
20
18.07
(0.05)
66.73
(0.75)
30.82
(0.82)
34.87
(0.87)
79.12
(0.13)
89.98
(0.02)
94.18
(0.18)
38.96
(0.98)
21
20.26
(0.29)
66.37
(0.38)
32.98
(0.97)
32.37
(0.39)
78.72
(0.70)
92.03
(0.05)
91.57
(0.58)
38.48
(0.49)
22
22.48
65.99
(0.99)
35.13
(0.14)
29.86
(0.86)
78.28
(0.26)
94.07
(0.08)
88.95
(0.95)
37.98
(0.99)
23
24.61
(0.64)
65.59
(0.57)
37.26
(0.26)
27.34
(0.34)
96.09
(0.11)
86.31
(0.32)
37.46
(0.40)
24
26.78
(0.79)
65.17
(0.18)
39.38
(0.37)
24.80
(0.81)
98.10
(0.13)
83.66
(0.68)
36.92
(0.91)
25
28.93
(0.94)
64.75
(0.74)
41.48
(0.48)
22.25
(0.27)
2700.09
(0.03)
81.00
(0.01)
36.38
(0.36)
26
64.27
(0.28)
43.57
(0.57)
19.70
02.07
(0.96)
78.33
(0.35)
35.77
(0.78)
27
63.79
(0.79)
45.64
(0.65)
17.12
(0.12)
04.03
(0.04)
75.64
(0.63)
35.16
(0.16)
28
63.29
(0.29)
47.69
(0.68)
14.54
(0.61)
05.98
(0.04)
72.94
(0.97)
34.52
(0.52)
29
49.73
(0.73)
11.94
(0.96)
07.92
70.24
(0.18)
33.87
(0.91)
30
09.32
(0.36)
09.84
67.51
(0.52)
Table IV
Calculated frequencies in vacuum wave numbers in two π−π bands of C2H2. The fractional parts of the measured frequencies are given in parentheses.
ν2+2ν40+ν51−ν41 Band center 3285.58
ν1+ν51−ν41 Band center 3479.47
J
R branch
P branch
R branch
P branch
1
3484.14
(0.14)
2
86.46
(0.48)
3474.74
(0.74)
3
88.67
72.36
(0.34)
4
91.07
(0.09)
69.98
(0.97)
5
93.35
(0.37)
67.47
6
3271.28
(0.20)
3271.32
(0.24)
95.63
(0.66)
3465.12
(0.10)
3465.17
(0.14)
7
68.86
(0.79)
68.91
(0.85)
97.89
(0.89)
62.68
62.78
8
66.43
(0.34)
66.48
(0.41)
3500.14
(0.18)
60.23
(0.22)
60.35
(0.34)
9
64.00
(0.92)
64.06
(0.99)
02.37
(0.39)
57.79
(0.77)
57.91
(0.90)
10
3310.75
(0.71)
3310.91
(0.89)
61.56
(0.50)
61.62
(0.57)
04.60
(0.58)
55.32
(0.31)
55.46
(0.45)
11
12.98
(0.95)
13.16
(0.09)
59.10
(0.07)
59.16
(0.12)
06.81
(0.80)
52.84
(0.84)
53.00
(0.00)
12
15.18
(0.18)
15.40
(0.36)
56.64
(0.60)
56.70
(0.66)
09.01
(0.02)
50.33
(0.34)
50.52
(0.53)
13
17.38
(0.46)
17.62
(0.61)
54.17
(0.17)
54.23
(0.25)
11.20
(0.18)
47.84
(0.86)
48.04
(0.05)
14
19.65
(0.64)
19.91
(0.81)
51.66
(0.66)
51.74
(0.73)
13.37
(0.38)
45.32
(0.30)
45.55
(0.55)
15
21.84
(0.76)
22.12
(0.03)
49.19
(0.17)
49.25
(0.23)
15.52
(0.51)
42.79
(0.79)
43.04
(0.05)
16
23.92
(0.95)
24.22
(0.24)
46.69
(0.68)
46.75
(0.73)
17.68
(0.67)
40.25
(0.26)
40.53
(0.53)
17
26.07
(0.08)
26.41
(0.43)
44.17
(0.16)
44.23
(0.21)
19.82
(0.80)
37.70
(0.69)
38.00
(0.00)
18
28.21
(0.23)
28.57
(0.59)
41.65
(0.64)
41.70
(0.68)
21.94
(0.94)
35.14
(0.14)
35.46
(0.46)
19
30.35
(0.37)
30.72
(0.80)
39.13
(0.14)
39.18
(0.16)
24.06
(0.11)
32.54
(0.56)
32.91
(0.90)
20
32.46
(0.46)
32.88
(0.90)
3236.60
(0.62)
26.16
(0.14)
29.97
(0.97)
30.35
(0.34)
21
34.56
(0.59)
35.00
(0.05)
34.05
(0.07)
28.24
(0.22)
27.37
(0.38)
27.77
(0.78)
22
36.65
(0.70)
37.13
(0.18)
31.48
(0.51)
30.31
(0.31)
24.75
(0.76)
25.17
(0.20)
23
38.74
(0.73)
39.24
(0.26)
28.91
(0.93)
32.37
(0.37)
22.12
(0.14)
22.60
(0.60)
24
40.80
(0.82)
41.34
(0.33)
26.32
(0.34)
34.42
(0.41)
25
42.84
(0.83)
43.42
(0.44)
23.72
(0.72)
26
44.88
(0.88)
45.49
(0.48)
21.11
(0.10)
27
46.91
(0.84)
47.55
(0.54)
18.49
(0.49)
28
48.92
(0.87)
49.60
(0.47)
15.86
(0.86)
29
50.91
(0.84)
51.63
(0.56)
13.22
30
52.89
(0.80)
53.65
(0.54)
10.56
(0.50)
31
54.86
(0.74)
55.66
(0.52)
07.89
(0.92)
32
56.41
(0.65)
57.62
(0.44)
33
58.74
(0.57)
59.62
(0.41)
Table V
Observed band centers, band origins, and changes in rotational constants of some bands of C2H2. All numerical quantities are expressed in vacuum-wave numbers.
Rotational constants calculated using average values of the doublet frequencies.
Table VI
Calculated and observed values of Δ2F for the ground state of C2H2 as obtained from several bands. For observed values only the fractional part is given.
J
Calc
ν1+ν51
ν2+ν41+ν51
ν3
ν2+ν51
3ν41+ν51
1
7.059
0.02
0.03
0.03
2
11.765
0.74
0.74
0.75
0.72
3
16.471
0.46
0.42
0.47
0.49
4
21.177
0.16
0.18
0.17
0.18
0.19
5
25.882
0.90
0.91
0.88
0.86
0.87
6
30.587
0.60
0.56
0.58
0.60
0.60
7
35.291
0.25
0.31
0.27
0.30
8
39.995
0.00
0.01
0.00
0.03
0.00
9
44.699
0.65
0.71
0.70
0.70
10
49.401
0.41
0.40
0.41
0.36
0.42
11
54.103
0.11
0.10
0.13
0.11
0.11
12
58.803
0.80
0.82
0.81
0.80
0.81
13
63.503
0.53
0.49
0.52
0.48
0.51
14
68.202
0.17
0.19
0.23
0.20
15
72.900
0.85
0.95
0.91
0.90
16
77.598
0.59
0.59
0.60
0.62
17
82.293
0.31
0.32
0.25
0.30
0.32
18
86.987
0.97
0.98
0.98
0.99
0.99
19
91.680
0.71
0.66
0.67
0.71
0.68
20
96.372
0.37
0.33
0.36
0.37
21
101.062
0.06
0.06
0.08
22
105.751
0.73
0.73
0.78
23
110.438
0.37
0.39
0.38
24
115.123
0.08
0.12
0.08
25
119.806
0.81
0.81
0.85
26
124.487
0.50
0.50
0.48
0.49
27
129.167
0.16
0.15
0.18
28
133.845
0.85
0.87
29
138.521
0.51
0.51
0.52
30
143.194
0.20
0.19
0.20
31
147.865
0.90
0.93
0.87
32
152.534
0.54
0.50
Table VII
Values of Bv and changes in B from the ground state for several vibrational states in C2H2. For π states the average value of the two levels is given.
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