62nd OSU International Symposium on Molecular Spectroscopy
WG06
Coupled-state analysis of rotational
transitions in the GT, GG, and GG’
conformers of n-propanol
Zbigniew Kisiel, Orest Dorosh
Institute of Physics, Polish Academy of Sciences
Atsuko Maeda, Frank C. De Lucia, Eric Herbst
Department of Physics, The Ohio State University
TT
TG (two identical)
Rotation
of CH2OH
about CC
GT
Rotation of OH about CO
GG
GG’
Most relevant previous studies:
Abdurakhmanov et al. : several papers over the period 19671987, cm-wave rotational studies of n-propanol.
gauche form estimated to be the most stable one.
Maeda et al. , Astrophys. J. Suppl. Ser. 162, 428 (2006): over
2400 lines of the GT conformer up to 375 GHz assigned and fitted
Kahn & Bruice, Chem.Phys.Chem. 6, 487 (2005): detailed ab
initio analysis of relative energies. In the preferred result GT is the
global minimum with GG, GG’ at 38, 52 cm-1, resp. TT,TG are at
28,45 cm-1, resp.
Present authors, RI14, 61st OSU Symposium: assignment of
GG and GG’ conformers on the basis of bands spotted in the FASSST
spectrum, using the AABS package. Preliminary analysis in terms of a
two state GG  GG’ fit.
Noted deficiency of the GT fit
A.Maeda, et al., Astrophys. J. Suppl. Ser. 162, 428 (2006)
17
15
Ka= 19
16
18
Distribution plot of obs-calc values for the GT conformer
symbol size is proportional to the magnitude of obs-calc.
Red circles are for obs-calc > 0.3 MHz and do not increase above o-c>0.7 MHz
Calculated spectroscopic observables for n-propanol:
A*
B
C
/MHz
DJ /kHz
DJK
DK
dJ
dK
GT
GG
14339
5102
4307
14100
5019
4280
GG’
14216
5034
4227
TT
26579
3784
3531
TG
26147
3734
3508
5.40
-23.8
64.1
1.59
11.9
5.09
-21.7
58.4
1.43
10.1
5.54
-25.9
69.6
1.65
11.2
m_a /D
m_b
m_c
0.71
0.87
0.96
0.56
1.04
1.09
1.39
0.12
0.87
0.09
1.46
0
1.15
0.39
1.15
m_tot
1.48
1.61
1.65
1.46
1.68
E** /cm-1
0
38
52
* Unscaled B3LYP/6-31G(d,p)
**Kahn & Bruice, Chem.Phys.Chem. 6, 487 (2005)
0.828
-2.35
58.7
0.0737
0.361
28
0.840
-2.61
57.6
0.0737
1.10
45
Confirmation of the assignment of the GT conformer
GT g.s.
A
B
C
/MHz
DJ /kHz
DJK
DK
dJ
dK
N
s
/kHz
14330.37308(45)
5119.30843(16)
4324.20213(16)
5.66401(22)
-24.6960(11)
67.8861(38)
1.687806(53)
12.56606(88)
2861
63.1
* Unscaled B3LYP/6-31G(d,p)
 =1
14378.5960(21)
5104.59867(93)
4318.31841(57)
5.74650(85)
-26.4520(35)
75.088(12)
1.71737(36)
13.027(14)
308
83.1
calculated*
14339
5102
4307
5.40
-23.8
64.1
1.59
11.9
Cavity-FTMW Stark measurements for GT n-propanol
Band A:
J = 17 16 of GG’
Band C:
Ka = 9  8 cQ+bQ of GG (white left),
GG’ (white right),
GT (yellow right)
Data set distribution plot for separate GT and GGGG’ fits
obs-calc differences are plotted
with symbol size proportional to
the magnitude of the difference.
Red circles are for
obs-calc > 0.3 MHz
Data set distribution plot for three state GTGGGG’ fit
obs-calc differences are plotted
with symbol size proportional to
the magnitude of the difference.
Red circles are for
obs-calc > 0.3 MHz
Principal terms in the Hamiltonian
Choice made along the lines used for ethanol, Pearson,Sastry,Herbst,De
Lucia , J. Mol. Spectrosc. 175, 246-261 (1996) with account for change
from Cs to C1 symmetry.
H =
Hrot(gt )
(Fac + …)(Pa Pc + Pc Pa) +
(Fab + …)(Pa Pb + Pb Pa)
(Fac + …)(Pa Pc + Pc Pa) +
(Fab + …)(Pa Pb + Pb Pa)
Hrot(gg )
+ DE(gg-gt)
(Fbc + …)(Pb Pc + Pc Pb) +
(Fab + …)(Pa Pb + Pb Pa)
(Ga + GaJ + GaK+…)Pa+
(Gb + GbJ + GbK+…)Pb+
(Gc + GcJ + GcK+…)Pc
(Fbc + …)(Pb Pc + Pc Pb) +
(Fab + …)(Pa Pb + Pb Pa)
(Ga + GaJ + GaK+…)Pa+
(Gb + GbJ + GbK+…)Pb+
(Gc + GcJ + GcK+…)Pc
Hrot(gg’ )
+ DE(gg’-gg)
GT
GG
GG’
Evidence for the magnitude of DE (GG-GT)
GT
Ka=1918 Q-branch
DE (GG-GT) = 47.8 cm-1
Ka=1514 Q-branch
GG
Three state ( GT  GG  GG’) fit n-propanol:
GT
A /MHz
B /MHz
C /MHz
DJ
DJK
DK
dJ
dK
/kHz
/kHz
/kHz
/kHz
/kHz
HJ
HJK
HKJ
HK
hJ
hJK
hK
/Hz
/Hz
/Hz
/Hz
/Hz
/Hz
/Hz
14330.37224(40)
5119.30723(14)
4324.20337(15)
GG
14207.302(16)
14257.477(16)
5036.43195(34) 5051.10933(40)
4290.1090(17)
4253.8584(17)
5.66005(27)
-26.543(30)
69.710(30)
1.687508(26)
12.051(23)
total lines
distinct fr.lines
5.33520(33)
-23.5239(70)
61.469(51)
1.49720(11)
11.775(13)
-0.000008(34)
0.0694(27)
-1.396(16)
2.574(18)
0.0009639(71)
-0.1042(16)
-0.648(25)
E /MHz -1433902.9(82)
E /cm-1
47.82985(27)
= 8340
= 6475
GG'
5.25074(44)
-21.156(29)
67.699(59)
1.56169(22)
11.521(26)
0.00213(12)
0.2295(36)
-1.796(14)
2.670(39)
0.006746(47)
-0.1530(38)
1.645(69)
0.0
0.0
micr rms /kHz
RMS error
0.00757(14)
-0.0664(69)
0.625(31)
0.660(52)
-0.002187(81)
0.0492(54)
-1.46(11)
90989.129(81)
3.0350707(27)
83.5
0.848
Interaction constants in the ( GT  GG  GG’) fit
x = a
x = b
x = c
GG-GG’:
Gx
GxJ
GxK
GxJJ
GxJK
GxKK
/MHz
/MHz
/MHz
/kHz
/kHz
/kHz
588.7(14)
-0.06567(50)
-0.1274(64)
0.02741(74)
-0.083(12)
0.094(60)
537.2363(90)
-0.029655(12)
-0.06133(55)
0.0007288(47)
-0.00665(58)
[ 0.]
96.90(95)
-0.01148(65)
0.538(43)
0.005315(33)
-0.10673(86)
[ 0.]
GT-GG:
Fx
/MHz
[0]
6.24(40)
10.89(11)
GT-GG’:
Fx
FxJ
FxK
/MHz
/MHz
/MHz
5.408(69)
[ 0.]
-35.33(37)
0.000731(34)
0.00795(25)
A total of 76 fitted constants = 3 x 15 in Hrot + 2 x DE + 29 in Hint
Jmax = 62, Kmax = 33
Comparison with ethanol
45
14
3.035 071(3) cm-1
GG’
90989.129(81)
GG
38
47.829 9(3) cm-1
GT
J.C.Pearson, et al., J. Mol. Spectrosc.
175, 246 (1996)
This work
Calc /cm-1
Principal conclusions:
A plausible three state fit is reported for the GTGGGG’ conformers
of n-propanol
The fit encompasses over 6400 distinct frequency lines measured in the
three states, at a satisfactorily overall deviation of fit of 85 kHz, and for
Jmax = 62, Kmax = 33.
The main result is
DE(GG - GT) = 47.829 9(3) cm-1
DE(GG’- GG) = 3.035 071(3) cm-1
and it constitutes a precise benchmark for ab initio, from which the best
current values are 38 and 14 cm-1, respectively.
In the second series, consisting of TT, TG+ and TG– conformers, the
vibrational energies are closer to each other than T, G+ and G– in ethanol
and the fit still poses a considerable challenge…