SUPPORTING INFORMATION FOR
First Spectroscopic Observation of Gold(I) butadiynylide:
Photodetachment Velocity Map Imaging of the AuC4H Anion
Bradley R. Visser1,‡, Matthew A. Addicoat2,#, Jason R. Gascooke3, Warren D. Lawrance3* and
Gregory F. Metha1*
1Department
2
of Chemistry, University of Adelaide, South Australia 5005, AUSTRALIA
Engineering and Science, Jacobs University Bremen Campus Ring 1, 28759 Bremen, GERMANY
3School
of Chemical & Physical Sciences, Flinders University, Adelaide, South Australia 5001,
AUSTRALIA
‡
Current address: General Energy Department, Paul Scherrer Institut, Villigen PSI 5232,
SWITZERLAND
#
Current address: Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität
Leipzig, Leipzig 04103, GERMANY
* To whom correspondence should be addressed
1
Circularisation Procedure
We have applied a circularisation procedure to the experimental photoelectron VMI images to
correct for small distortions within the image. These distortions arise from stray electric and
magnetic fields and are a known issue in the measurement of electron VMI images, first noted by
Parker and Eppink in their original description of the VMI technique. [D.H. Parker and A.T.J.B.
Eppink, J. Chem. Phys. 107, 2357, (1997)]. They noted increased energy resolution was obtained
when integrating over a small angular range. Furthermore, subsequent researchers have also
noticed distortions and consequently choose the “best” quadrant for analysis. Rather than limiting
the data used in order to improve the spectrum, we correct the image so we can use all of the
data.
We start by noting that after analysing many photoelectron VMI images we find the distortions are
approximately linear with radial distance from the centre of the electron image. We therefore
slice the image into a series of wedges of chosen angle. One wedge is used as a reference wedge
to which all other wedges are compared. The scaling factor necessary to map the radial
dependence of each wedge onto the reference wedge are thus determined. These scaling factors
are subsequently used to radially expand or compress each wedge to generate a circularized
image.
As an example, we take the 610nm photodetachment image of AuC4H used in the current study.
Four sets of radial scaling parameters were determined by using four different 20° reference
wedges at 45°, 135°, 225° and 315°. These data were fit simultaneously to a trigonometric series of
the form A0 
 A cos(n )  B sin( n ) . It was found that using terms up to n = 5 gave an
n
n
n 1
adequate representation of the scaling parameter variations with angle. Using these fitted
2
parameters, 6° wedges of the original image were isolated and individually scaled by the
determine scaling factor to finally form the circularised image. Scaling parameters were
determined to vary between 0.9828 and 1.0133 for the image under investigation, meaning that
the outermost ring deviates at most 3.0 pixels away from circularity. Photoelectron spectra
generated by applying the inverse Abel transform to the original image and the circularised image
are compared in Figure S1. It is clear that the overall appearance of the spectra is unchanged and
the peak widths using the circularized image are slightly narrower than when the original image is
used. There is, however, an apparent shift between the two spectra due to the image not being
isotropic. In the current example, the regions with higher electron count have been stretched
during the circularisation procedure.
In the present case the non-circularity is small compared to the distance between rings in the
image. If the non-circularities are large then it becomes critically important to circularise the image
in order to obtain the correct anisotropy value for each ring. Note that the anisotropy parameters
extracted from the 610 nm photodetachment image are found to be almost identical when
processing the original image or the circularised image.
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Intensity
Circularised
Raw
0
2.00
1.95
1.90
1.85
1.80
1.75
1.70
Binding Energy (eV)
Figure S1: Comparison of the photoelectron spectra of AuC4H following photodetachment at 610
nm when using the original experimental image (black line) and using the image generated by the
circularisation procedure (blue line).
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Figure S2: The lowest energy anion and neutral geometries obtained for AuC4 from the ADF
calculations. Electronic energies are given relative to the global minimum neutral structure. The
units for bond length are Angstrom and degrees for bond angle.
Figure S3: The lowest energy anion and neutral geometries obtained for AuC 4H2 from the ADF
calculations. Electronic energies are given relative to the global minimum neutral structure. The
units for bond length are Angstrom and degrees for bond angle.
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2
1
Aʺ  Aʺ
2
3
 
Figure S4: Simulated Franck-Condon spectra for the 2A′′  1A′′ (top) and 2  3 (bottom)
transitions of AuC4. The simulated stick spectra are convoluted with a Gaussian function of 10
meV FWHM to approximate the experimental resolution.
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2
2
1 +
 
1
g  g
+
Figure S5: Simulated Franck-Condon spectra for the 2  1+ (top) and 2g  1g+ (bottom)
transitions of the two different AuC4H2 isomers The simulated stick spectra are convoluted with a
Gaussian function of 10 meV FWHM to approximate the experimental resolution
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Mode
ω1
ω2
ω3
Vibration Description
Sym.
3
2
Sym.
1A′′
2A′′
C4 symmetric stretch
+
2049
2120
a'
2014
2016
C4 anti-symmetric stretch
+
1811
1836
a'
1822
1751
C4 symmetric stretch
+
967
1019
a'
971
1017
(C-C and C-C bonds)
(C-C bond)
ω4a
C4 alternate bend

546
508
a'
519
432
ω4b
"
"
"
"
a"
440
310
ω5
Au-C4 stretch
+
275
346
a'
388
345
ω6a
C4 fundamental bend

251
258
a'
227
241
ω6b
"
"
"
"
a"
208
-
ω7a
Au-C-C3 bend

127
142
a'
89
96
ω7b
"
"
"
"
a"
-
58
2.54
0.08
3.39
0
E
(eV)
Table S1
Calculated harmonic vibrational frequencies (cm−1) and relative energies (eV) for the 2, 2A′′, 3
and 1A′′ states of AuC4−/0. The linear 2 and 3 states have 10 vibrations consisting of 4 stretches
and 3 degenerate bending vibrations (4a,b, 6a,b and 7a,b). The bent 1A′′ and 2A′′ states each have
9 non-degenerate vibrations.
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Mode
Vibration Description
Sym.
 
g
2
ω1
Anti-sym. C-H stretch
u+
3353
3345
ω2
Sym. C-H stretch
g+
3352
3345
ω3
Sym. Au-C stretch
g+
1967
1951
ω4
Anti-sym. Au-C stretch
u+
1956
1942
ω5a,b
H-C-C bend
g
530
715
ω6a,b
C-C-H bend 
u
530
713
ω7
Au-C2H sym. stretch
g+
442
469
ω8
HAu-C4H stretch
u+
417
456
ω9a,b
Au-C-CH bend
u
379
404
ω10a,b
Au-C-CH bend
g
249
283
ω11a,b
HC2-Au-C2H bend
u
70
104
.05
0
E
g
(eV)
Table S2
Calculated harmonic vibrational frequencies (cm−1) and relative energies (eV) for the 1g and 2g
states of the HC2AuC2H−/0 isomer. Both states are linear and have 16 vibrations consisting of 6
stretches and 5 degenerate bending vibrations (5a,b, 6a,b, 9a,b, 10a,b and 11a,b).
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Mode
Vibration Description
Sym.

2
ω1
C-H stretch
+
3391
3362
C4 symmetric stretch
+
2132
2145
ω2
(C-C and C-C bonds)
ω3
Au-H stretch
+
1993
2091
ω4
C4 anti-symmetric stretch
+
1958
1927
C4 symmetric stretch
+
967
1008
ω5
(C-C bond)
ω6a,b
H-Au-CC3H bend

616
643
ω7a,b
C4 alternate bend

501
587
ω8a,b
HAuC3-C-H bend

424
519
ω9
HAu-C4H stretch
+
280
300
ω10a,b
C4 fundamental bend

275
292
ω11a,b
H-Au-C4H bend

91
156
.02
0.24
E
(eV)
Table S3
Calculated harmonic vibrational frequencies (cm−1) and relative energies (eV) for the 1 and 2
states of the HAuC4H−/0 isomer. Both states are linear and have 16 vibrations consisting of 6
stretches and 5 degenerate bending vibrations (6a,b, 7a,b, 8a,b, 10a,b and 11a,b).
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