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Microwave spectrum of 12CH317OH
JOURNAL OF MOLECULAR SPECTROSCOPY 148,506-508 (1991)
NOTES Microwave
Spectrum of ‘*CH3”0H
We report the microwave spectrum of “CHs”OH and its molecular constants for the first time. The sample was a 90% enriched CHs’*OH purchased from Merck Frosst Canada, Inc., which contained about i’ib of ‘*CH3”0H. A conventional Stark-modulated spectrometer was used to observe the K = 2 + 1 Qbranch series of the E-species and the a-type JK = 10 + 00, 2K + lK lines of both the A- and E-species of ‘*CH “OH in its ground torsional state. ine observed frequencies of the K = 2 + 1, E Q-branch lines are listed in Table I. The frequencies between J = 2 and 12 were least-squares fitted to a power series expansion of J(J + 1) as “J = V, t uJ(J t 1) t b.P(J + 1)2 + c.P(J + 1)’ + 0Y(J t 1)4, where the series origin V, = 29697.79( 1.12) MHz, a = -1.702( 105) MHz, b x lo* = 9.82(27) MHz, c X lo5 = -2.696(2.607) MHz, and d X 10’ = -3.758(807) MHz with 30 errors in parentheses which apply to the last significant digits. The standard deviation of the fit was 0.38 MHz. The observed frequencies of eight a-type lines are listed in Table II. The JK = l,, + O0lines show hyperfine splittings due to the nuclear quadrupole moment of “0 (I = 5/2), from which the x,, component of the quadrupole coupling tensor was determined to be -7.86( 11) MHz. It was difficult to determine the other independent parameter, xbb - x,, because the 2,, + 1r,, and 2r2 * 1 ,, , A lines exhibited only partially resolved hyperline components. Therefore we estimated the X, value to be - 11 MHz by referring to those of HZ”0 (I) and C2H4”0 (2), which gives the value of xbb - X, - - 15 MHz. The hypothetical unsplit frequencies(YO)ofthe2,, + li0and2i2+ 1I ,, A transitions were obtained by using xbb - X, thus estimated and X, determined above. Although this estimate is crude, the accuracy of the hypothetical frequencies is not so bad because they are insensitive to the variation of x bb- x, (kSS than 0.1 MHZ for 5 MHZ VatiatiOn of & - X,). The hyperhne splittings of the other J = 2 6 1 lines were not resolved, and we assumed that the observed frequencies were equal to the hypothetical unsplit frequencies. Since the information from the observed frequencies is not enough to determine all the molecular constants listed in Table IV, we fixed the following parameters at constant values to analyze the observed frequencies; the moment of inertia about the u-axis (the internal axis), I,, was estimated by using the structural parameters TABLE I
K = 2 + 1, E Q-Branch Transitions (MHz) J
%h.
(O-C)
(0-C)
J
Voh*
2
29690.76’
(-0.34)
10
30607.49
( 0.05)
18
35213.29
29691.91 a ( 0.47)
11
31007.29
(-0.14)
19
35573.81
(-0.04)
20
35717.89
4
29702.73
( 0.00)
12
31496.32
5
29734.06
( 0.02)
13
32068.47
21
35600.79
6
29796.12
(-0.17)
14
32707.20
22
35290.93
7
29901.82
(-0.60)
15
33384.69
23
34471.03
8
30063.92
(-0.04)
16
34062.14
9
30295.58
( 0.16)
17
34690.31
Accuracy of thii line is O.lh4Hz. accuracy of others is 0.05MHz
0022-2852191 $3.00 0
““Il.
3
’
CopyriSht
J
1991by Academic Press. Inc.
All rights of reproduction
in any form reserved.
506
507
NOTES TABLE II n-Type Transitions of CHg “OH (MHz) Transition
Species
‘,,+%I
A
‘o+Oo
Ft
E
F
5nesn In+5n
47315.06
3n+5/2
47315.71
1.07(4.03)
5/2csn
47317.72
-1.27(-0.02)
ltZt5R
47319.42
0.43( 0.03)
3n+5n
47320.08
1.09(-0.01)
202+
‘01
A
2ll+
IlO
A
7n+sn
95433.48
9nh7n
95435.70
112 + 5n
93829.56
9nc7n
93831.19
20+ 2.,+ 21+-
a
41
A
“0’
47313.38
_d
2,2@
hfshb
“*’
94626.42
-1.26(
47314&a(5)
0.00)
0.42( 0.03)
47318.99(5)
-
94626.4 (5)
-1.65(-0.25)
95435.1 (5)
0.57( 0.25) -0.90(-0.09)
93830.5 (5)
0.76( 0.09)
10
E
_d
94629.91
-
94629.9 (5)
1.1
E
_d
94624.34
-
94624.3 (5)
E
_d
94637.11
‘1
94637.2 (5)
Accuracy is better than O.OSMHzfor completelyresolvedlines ( I,, e Ow and 1, + 0, )
and is O.IMHzfor other lines. b (Observed hyperfine splitting - Calculated hyperfine splitting) in parentheses after hfs,. E v, = hypotheticalunsplitfrequency d Not resolved
given by Gerry et al. (3) and the values of I, of “CH, 160H (4) and “CH, ‘*OH (3); the values of lab, Inz, two u-type parameters, G, and L,, and a centrifugal distortion constant, DK, are fixed to be the averages of corresponding parameters of “CH3 160H (4, 5) and 12CHS“OH (3, 6). The observed a-type lines and the observed K = 2 + 1, E Q-branch lines with J = 2-12 were fitted to the a-type parameters B, C, F”;, D,, and DJK, and the potential barrier height V, with an rms deviation of 0.42 MHz. The results are listed in Tables III and IV. We estimated the errors of I,, and Ia2using those of the structural parametefi of ‘%H,‘60H (4) and 12CHS‘*OH (3) 1which are related to the error of Vj. It is to be noted that the obtained barrier height V, of ‘2CH3’70H is between that of ‘2CH,‘60H and that of ‘2CH3180H.
TABLE III Barrier Height (cm-‘) and Inertial Constants (amu. A2) of CH3”0HB
“3 375.293(60)
’
I 11 0.75444(13)
I 12
b
3.21187(35)
Conversionfactor= 505376MHzw1wA?
b
‘b
4
20.94127(16)
21.72978(11)
The errors for V,, I,, and I, ¬e
the last digits of the constants. b Estimated from structural parameters of CHPOH and CH+OH.
I ab
-0.10815
b
3 D and apply to
508
NOTES TABLE IV Molecular Constants of CH3”OH (MHz)” A
127439.2(15.4) b
F”
-69.55(6)
B
24132.43(B)
G”
-3.436 ’
C
23257.30(12)
L
0.047 c
-124.63 b
D,
0.0495(180)
DIK
0.2844(X?)
Da
1.314 c
D sb p (unitless) F
0.8099117 b 827708.4 ’
Valuesin parentheses denote 3 TVand apply to the last digiu of the constants. b Calculated from strucmral parameters given in TablelII. ’
Averageof theCH@OH andCHII*OHvalues.
ACKNOWLEDGMENTS We are grateful to Dr. J. T. Hougen for helpful discussions and to Professor E. Hirota for his critical reading of the manuscript. REFERENCES 1. 2. 3. 4. 5. 6.
J. VERHOEVEN, A. DYMANUS, AND H. BLUYSSEN, J. Chem. Phys. SO, 3330-3338 (1969). R. A. CRESWELLAND R. H. SCHWENDEMAN,Chem. Phys. Lett. 21,521-524 ( 1974). M. C. L. GERRY, R. M. LEES, AND G. WINNEWISSER, J. Mol. Spectrosc. 61,231-242 ( 1976). R. M. LEES AND J. G. BAKER, .I Chem. Phys. 48,5299-53 18 ( 1968). E. HERBST, J. K. MESSER, F. C. DE LUCIA, AND P. HELMINGER, .I. Mol. Spectrosc. 108,42-57 ( 1984). Y. HOSHINO, M. OHISHI, AND K. TAKAGI, to be published. YOSHIAKI HOSHINO MASATOSHI OHISHI’ KOJIRO TAKACI
Department of Physics Toyama University Gofuku. Toyama 930, Japan Received March 28, 1991 ’ Present address: Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 38413, Japan.
NOTES Microwave
Spectrum of ‘*CH3”0H
We report the microwave spectrum of “CHs”OH and its molecular constants for the first time. The sample was a 90% enriched CHs’*OH purchased from Merck Frosst Canada, Inc., which contained about i’ib of ‘*CH3”0H. A conventional Stark-modulated spectrometer was used to observe the K = 2 + 1 Qbranch series of the E-species and the a-type JK = 10 + 00, 2K + lK lines of both the A- and E-species of ‘*CH “OH in its ground torsional state. ine observed frequencies of the K = 2 + 1, E Q-branch lines are listed in Table I. The frequencies between J = 2 and 12 were least-squares fitted to a power series expansion of J(J + 1) as “J = V, t uJ(J t 1) t b.P(J + 1)2 + c.P(J + 1)’ + 0Y(J t 1)4, where the series origin V, = 29697.79( 1.12) MHz, a = -1.702( 105) MHz, b x lo* = 9.82(27) MHz, c X lo5 = -2.696(2.607) MHz, and d X 10’ = -3.758(807) MHz with 30 errors in parentheses which apply to the last significant digits. The standard deviation of the fit was 0.38 MHz. The observed frequencies of eight a-type lines are listed in Table II. The JK = l,, + O0lines show hyperfine splittings due to the nuclear quadrupole moment of “0 (I = 5/2), from which the x,, component of the quadrupole coupling tensor was determined to be -7.86( 11) MHz. It was difficult to determine the other independent parameter, xbb - x,, because the 2,, + 1r,, and 2r2 * 1 ,, , A lines exhibited only partially resolved hyperline components. Therefore we estimated the X, value to be - 11 MHz by referring to those of HZ”0 (I) and C2H4”0 (2), which gives the value of xbb - X, - - 15 MHz. The hypothetical unsplit frequencies(YO)ofthe2,, + li0and2i2+ 1I ,, A transitions were obtained by using xbb - X, thus estimated and X, determined above. Although this estimate is crude, the accuracy of the hypothetical frequencies is not so bad because they are insensitive to the variation of x bb- x, (kSS than 0.1 MHZ for 5 MHZ VatiatiOn of & - X,). The hyperhne splittings of the other J = 2 6 1 lines were not resolved, and we assumed that the observed frequencies were equal to the hypothetical unsplit frequencies. Since the information from the observed frequencies is not enough to determine all the molecular constants listed in Table IV, we fixed the following parameters at constant values to analyze the observed frequencies; the moment of inertia about the u-axis (the internal axis), I,, was estimated by using the structural parameters TABLE I
K = 2 + 1, E Q-Branch Transitions (MHz) J
%h.
(O-C)
(0-C)
J
Voh*
2
29690.76’
(-0.34)
10
30607.49
( 0.05)
18
35213.29
29691.91 a ( 0.47)
11
31007.29
(-0.14)
19
35573.81
(-0.04)
20
35717.89
4
29702.73
( 0.00)
12
31496.32
5
29734.06
( 0.02)
13
32068.47
21
35600.79
6
29796.12
(-0.17)
14
32707.20
22
35290.93
7
29901.82
(-0.60)
15
33384.69
23
34471.03
8
30063.92
(-0.04)
16
34062.14
9
30295.58
( 0.16)
17
34690.31
Accuracy of thii line is O.lh4Hz. accuracy of others is 0.05MHz
0022-2852191 $3.00 0
““Il.
3
’
CopyriSht
J
1991by Academic Press. Inc.
All rights of reproduction
in any form reserved.
506
507
NOTES TABLE II n-Type Transitions of CHg “OH (MHz) Transition
Species
‘,,+%I
A
‘o+Oo
Ft
E
F
5nesn In+5n
47315.06
3n+5/2
47315.71
1.07(4.03)
5/2csn
47317.72
-1.27(-0.02)
ltZt5R
47319.42
0.43( 0.03)
3n+5n
47320.08
1.09(-0.01)
202+
‘01
A
2ll+
IlO
A
7n+sn
95433.48
9nh7n
95435.70
112 + 5n
93829.56
9nc7n
93831.19
20+ 2.,+ 21+-
a
41
A
“0’
47313.38
_d
2,2@
hfshb
“*’
94626.42
-1.26(
47314&a(5)
0.00)
0.42( 0.03)
47318.99(5)
-
94626.4 (5)
-1.65(-0.25)
95435.1 (5)
0.57( 0.25) -0.90(-0.09)
93830.5 (5)
0.76( 0.09)
10
E
_d
94629.91
-
94629.9 (5)
1.1
E
_d
94624.34
-
94624.3 (5)
E
_d
94637.11
‘1
94637.2 (5)
Accuracy is better than O.OSMHzfor completelyresolvedlines ( I,, e Ow and 1, + 0, )
and is O.IMHzfor other lines. b (Observed hyperfine splitting - Calculated hyperfine splitting) in parentheses after hfs,. E v, = hypotheticalunsplitfrequency d Not resolved
given by Gerry et al. (3) and the values of I, of “CH, 160H (4) and “CH, ‘*OH (3); the values of lab, Inz, two u-type parameters, G, and L,, and a centrifugal distortion constant, DK, are fixed to be the averages of corresponding parameters of “CH3 160H (4, 5) and 12CHS“OH (3, 6). The observed a-type lines and the observed K = 2 + 1, E Q-branch lines with J = 2-12 were fitted to the a-type parameters B, C, F”;, D,, and DJK, and the potential barrier height V, with an rms deviation of 0.42 MHz. The results are listed in Tables III and IV. We estimated the errors of I,, and Ia2using those of the structural parametefi of ‘%H,‘60H (4) and 12CHS‘*OH (3) 1which are related to the error of Vj. It is to be noted that the obtained barrier height V, of ‘2CH3’70H is between that of ‘2CH,‘60H and that of ‘2CH3180H.
TABLE III Barrier Height (cm-‘) and Inertial Constants (amu. A2) of CH3”0HB
“3 375.293(60)
’
I 11 0.75444(13)
I 12
b
3.21187(35)
Conversionfactor= 505376MHzw1wA?
b
‘b
4
20.94127(16)
21.72978(11)
The errors for V,, I,, and I, ¬e
the last digits of the constants. b Estimated from structural parameters of CHPOH and CH+OH.
I ab
-0.10815
b
3 D and apply to
508
NOTES TABLE IV Molecular Constants of CH3”OH (MHz)” A
127439.2(15.4) b
F”
-69.55(6)
B
24132.43(B)
G”
-3.436 ’
C
23257.30(12)
L
0.047 c
-124.63 b
D,
0.0495(180)
DIK
0.2844(X?)
Da
1.314 c
D sb p (unitless) F
0.8099117 b 827708.4 ’
Valuesin parentheses denote 3 TVand apply to the last digiu of the constants. b Calculated from strucmral parameters given in TablelII. ’
Averageof theCH@OH andCHII*OHvalues.
ACKNOWLEDGMENTS We are grateful to Dr. J. T. Hougen for helpful discussions and to Professor E. Hirota for his critical reading of the manuscript. REFERENCES 1. 2. 3. 4. 5. 6.
J. VERHOEVEN, A. DYMANUS, AND H. BLUYSSEN, J. Chem. Phys. SO, 3330-3338 (1969). R. A. CRESWELLAND R. H. SCHWENDEMAN,Chem. Phys. Lett. 21,521-524 ( 1974). M. C. L. GERRY, R. M. LEES, AND G. WINNEWISSER, J. Mol. Spectrosc. 61,231-242 ( 1976). R. M. LEES AND J. G. BAKER, .I Chem. Phys. 48,5299-53 18 ( 1968). E. HERBST, J. K. MESSER, F. C. DE LUCIA, AND P. HELMINGER, .I. Mol. Spectrosc. 108,42-57 ( 1984). Y. HOSHINO, M. OHISHI, AND K. TAKAGI, to be published. YOSHIAKI HOSHINO MASATOSHI OHISHI’ KOJIRO TAKACI
Department of Physics Toyama University Gofuku. Toyama 930, Japan Received March 28, 1991 ’ Present address: Nobeyama Radio Observatory, Nobeyama, Minamimaki, Minamisaku, Nagano 38413, Japan.