1. Iodine: Many Electrons and Much to Discuss… The Nuclear Quadrupole Coupling, Nuclear Spin-Rotation, Conformational Analysis, and Structural Determination of 2-Iodobutane
Eric A. Arsenault, Daniel A. Obenchain, Yoon Jeong Choi,
Thomas A. Blake, Stephen A. Cooke, and Stewart E. Novick,

2. 2-iodobutane
gauche’ (g’)
anti (a)
gauche (g)

3. Spectroscopic Parameters of a-, g-, and g’-2-iodobutane
A (MHz)
(8)a
(11)
(7)
B (MHz)
(18)
(12)
(26)
C (MHz)
(11)
(7)
(38)
DJ (kHz)
0.0908(16)
0.3488(14)
0.3546(29)
DJK (kHz) —
-0.618(18)
DK (kHz)
-6.12(25)
1.043(7)
4.54(7)
d1 (kHz)
(11)
(10)
-0.088(4)
d2 (kHz)
(35)
χ aa (MHz)
(13)
(2)
(6)
χ bb (MHz)
(12)
(14)
(11)
χ cc (MHz)
(17)
(14)
(12)
χ ab b (MHz)
(35)
(20)
(4)
χ ac (MHz)
(28)
(5)
(6)
χ bc (MHz)
-92.25(7)
(32)
(4)
Caa (kHz)
4.0(7)
2.85(11)
2.7(5)
Cbb (kHz)
3.74(22)
4.69(12)
4.18(30)
Ccc (kHz)
4.47(24)
3.65(7)
3.52(27)
Nlinesc
102
212 72
RMSd (kHz)
3.8
2.7
3.0
aNumbers in parentheses give standard errors (1𝜎, 67% confidence level) in units of the least significant figure.
bThe signs of the off-diagonal quadrupole coupling constants can not be exactly determined.
It is only known that χ ab χ a𝑐 χ bc is negative1. These terms are presented with signs in accordance with the ab initio results.
cNumber of transitions used in the fit.
dRoot mean square deviation of the fit, obs−calc 2 / N lines
1Spoerel, U.; Dreizler, H.; Stahl, W. Zeitschrift fur Naturforschung A 1994, 49,

4. Nuclear Quadrupole Coupling Tensor of Iodine in a-, g-, and g’-2-iodobutane
Parameters a g g’
χ zz (MHz)
(21)a
(23)
(4)
χ y𝑦 (MHz)
(18)
(20)
862.95(4)
χ xx (MHz)
(20)
(28)
867.14(5)
𝜂 χ b
(16)
(20)
(4)
aNumbers in parentheses give standard errors (1𝜎, 67% confidence level) in units of the least significant figure.
b is a measure of the asymmetry of the nuclear quadrupole coupling tensor, where 𝜂 𝜒 = 𝜒 𝑥𝑥 − 𝜒 𝑦𝑦 𝜒 𝑧𝑧 g’ a g

5. 13C Isotopologues of g-2-iodobutane
Cavity Spectra
Chirp Spectra

6. Spectroscopic Parameters of g-2-iodobutane
Prediction
g-Parent
13C1
13C2
13C3
13C4
A (MHz)
3612
(11)a
(26)
(30)
(8)
(8)
B (MHz)
1645
(12)
(9)
(12)
(18)
(14)
C (MHz)
1189
(7)
(9)
(13)
(20)
(14)
DJ (kHz) —
0.3488(14)
0.3386(15)
0.3441(20)
0.3385(32)
0.3478(24)
DK (kHz)
1.043(7)
[1.043]
d1 (kHz)
(10)
[ ]
d2 (kHz)
(35)
[ ]
χ aa (MHz)
-684
(2)
(13)
(6)
(23)
(17)
χ bb (MHz)
272
(14)
(14)
(11)
(27)
(20)
χ cc (MHz)
411
(14)
(19)
(13)
(36)
(27)
χ ab b (MHz)
-441
(20)
(13)
(12)
(33)
(20)
χ ac (MHz)
-212
(5)
(31)
(31)
-461.4(7)
451.6(5)
χ bc (MHz)
-85
(32)
(30)
(17)
(44)
(28)
Caa (kHz)
2.85(11)
[2.85]
Cbb (kHz)
4.69(12)
[4.69]
Ccc (kHz)
3.65(7)
[3.65]
Nlinesc
212 39 58 38 40
RMS d (kHz)
2.7
0.8
1.7
1.6
1.2
aNumbers in parentheses give standard errors (1𝜎, 67% confidence level) in units of the least significant figure.
bThe signs of the off-diagonal quadrupole coupling constants can not be exactly determined.
It is only known that χ ab χ a𝑐 χ bc is negative. These terms are presented with signs in accordance with the ab initio results.
cNumber of transitions used in the fit.
dRoot mean square deviation of the fit, obs−calc 2 / N lines
1Spoerel, U.; Dreizler, H.; Stahl, W. Zeitschrift fur Naturforschung A 1994, 49,

7. r0 Structural Parameters for g-2-iodobutane
Bond Length (Å)
C1-C2
1.536(12)a
C2-C3
1.497(6)
C3-C4
1.548(6)
I-C2
2.166(4)
Bond Angle (°)
∠(C1-C2-C3)
112.9(10)
∠(C2-C3-C4)
114.17(23)
Dihedral (°)
(C1-C2-C3-C4)
172.7(16)
(I-C2-C3-C4)
-63.85(31)
Structural Fit Error
χ 2
0.0024 𝜎
0.018
aNumbers in parentheses give standard errors (1𝜎,
67% confidence level) in units of the least significant figure.

8. Kraitchman Coordinates for g-2-iodobutane
Atoms
Kraitchman Coordinates
ab initio Coordinates
|a|
|b|
|c| a b c C1
1.2170(12)a
2.1389(7)
0.05(29)i
1.2
2.2
-0.023 C2
1.1801(13)
0.6646(23)
0.370(4)
0.67
0.37 C3
2.2422(7)
0.132(11)
0.354(4)
2.3
-0.15
-0.36 C4
2.3616(6)
1.6019(9)
0.113(13)
2.4
-1.6
0.13
aNumbers in parentheses give standard errors (1, 67% confidence level) in units of the least signifigant figure.
𝛼 2 = Δ 𝑃 𝛼 𝜇 1+ Δ𝑃 𝛽 𝐼 𝛼 − 𝐼 𝛽 Δ𝑃 𝛾 𝐼 𝛼 − 𝐼 𝛾
Δ 𝑃 𝛼 = 1 2 (− Δ𝐼 𝛼 + Δ𝐼 𝛽 + Δ𝐼 𝛾 )
Δ𝐼 𝛼 = 𝐼′ 𝛼 − 𝐼 𝛼

9. Spectroscopic Parameters of g-2-iodobutane
Prediction
g-Parent
13C1
13C2
13C3
13C4
A (MHz)
3612
(11)a
(26)
(30)
(8)
(8)
B (MHz)
1645
(12)
(9)
(12)
(18)
(14)
C (MHz)
1189
(7)
(9)
(13)
(20)
(14)
DJ (kHz) —
0.3488(14)
0.3386(15)
0.3441(20)
0.3385(32)
0.3478(24)
DK (kHz)
1.043(7)
[1.043]
d1 (kHz)
(10)
[ ]
d2 (kHz)
(35)
[ ]
χ aa (MHz)
-684
(2)
(13)
(6)
(23)
(17)
χ bb (MHz)
272
(14)
(14)
(11)
(27)
(20)
χ cc (MHz)
411
(14)
(19)
(13)
(36)
(27)
χ ab b (MHz)
-441
(20)
(13)
(12)
(33)
(20)
χ ac (MHz)
-212
(5)
(31)
(31)
-461.4(7)
451.6(5)
χ bc (MHz)
-85
(32)
(30)
(17)
(44)
(28)
Caa (kHz)
2.85(11)
[2.85]
Cbb (kHz)
4.69(12)
[4.69]
Ccc (kHz)
3.65(7)
[3.65]
Nlinesc
212 39 58 38 40
RMS d (kHz)
2.7
0.8
1.7
1.6
1.2
aNumbers in parentheses give standard errors (1𝜎, 67% confidence level) in units of the least significant figure.
bThe signs of the off-diagonal quadrupole coupling constants can not be exactly determined.
It is only known that χ ab χ a𝑐 χ bc is negative. These terms are presented with signs in accordance with the ab initio results.
cNumber of transitions used in the fit.
dRoot mean square deviation of the fit, obs−calc 2 / N lines
1Spoerel, U.; Dreizler, H.; Stahl, W. Zeitschrift fur Naturforschung A 1994, 49,

10. NQC Tensor of Iodine in g-2-iodobutane
Parameters
g-Parent
13C1
13C2
13C3
13C4
χ zz (MHz)
(23)
(14)
(13)
(34)
(23)
χ y𝑦 (MHz)
(20)
888.34(8)
888.61(9)
888.60(24)
888.51(16)
χ xx (MHz)
(28)
842.88(14)
842.89(14)
842.63(35)
842.74(25)
𝜂 χ b
(20)
(9)
(10)
(25)
(17)
aNumbers in parentheses give standard errors (1𝜎, 67% confidence level) in units of the least significant figure.
b is a measure of the asymmetry of the nuclear quadrupole coupling tensor, where 𝜂 𝜒 = 𝜒 𝑥𝑥 − 𝜒 𝑦𝑦 𝜒 𝑧𝑧

11. What is causing this difference?
Missing term in Hamiltonian of 13C isotopologue?
Additional nuclear spin rotation interaction due to
𝜇𝐼 of 13C
1.) Not necessary in any other 13C isotopologue
2.) Term did not fit
Spin-spin interaction between 127I (𝐼=5/2) and 13C (𝐼=1/2)
1.) Term only on the order of 2 kHz
2.) Term did not fit well
3.) Did not change value of χ zz
Change in C-I bond length upon isotopic substitution

12. What is causing this difference
What is causing this difference? Change in C-I bond length upon isotopic substitution.
Bond length was scaled using ab initio frequency of the normal mode that most resembled a C-I stretch and the reduced mass of 12C-127I and 13C-127I
Found a decrease in bond length of 1.8 mÅ
Scaled 13C-127I bond length was used in ab initio to predict change in NQC tensor
Suggests a 230 kHz decrease in χ zz for 13C2
Experimentally observed decrease in χ zz was 199(13) kHz
Predictions of 𝛘
Based on Initial Structure
From 13C2 bond length correction
χ zz (MHz)
χ y𝑦 (MHz)
χ xx (MHz)

13. Acknowledgements