The spectrum of nickel monoxide between 410 and 510 nm: Laser-induced fluorescence and dispersed fluorescence measurements

Article abstract of DOI:10.1016/j.cplett.2003.12.089

The products from the reaction of laser-ablated Ni atoms with CH ₄, O₂ and NO have been studied via laser-induced and dispersed fluorescence spectroscopies. NiC, NiH and NiO species have been detected between 410 and 510 nm. Twenty N

Full text of DOI:10.1016/j.cplett.2003.12.089

Chemical Physics Letters 385 (2004) 239–243
www.elsevier.com/locate/cplett
The spectrum of nickel monoxide between 410 and 510 nm:
laser-induced fluorescence and dispersed fluorescence measurements
1
Walter J. Balfour , Jianying Cao, Roy H. Jensen , Runhua Li
*
Department of Chemistry, University of Victoria, P.O. Box 3055, Victoria, BC, Canada V8W 3P6
Received 14 October 2003; in final form 19 November 2003
Published online: 19 January 2004
Abstract
The products from the reaction of laser-ablated Ni atoms with CH4, O2 and NO have been studied via laser-induced and dis-
persed fluorescence spectroscopies. NiC, NiH and NiO species have been detected between 410 and 510 nm. Twenty NiO bands have
been rotationally analyzed for the first time and, in most instances, measurements of the 58NiO/60NiO isotopic shifts have been
made. Dispersed fluorescence data have been collected at two excitation wavelengths, corresponding to two prominent LIF bands –
near 479.1 and 474.5 nm. Vibrational energies for all ground state levels up to v ¼ 9 have been determined.
Ó 2004 Elsevier B.V. All rights reserved.
1. Introduction
man-Hill and Field [11], and by Ram and Bernath [12]
ꢀ
3
have established the ground state to be a case a R
In the course of examining excitation spectra between
410 and 510 nm in the reaction of laser-ablated nickel
and helium doped with methane, we inadvertently ob-
served bands of NiO. These bands have been briefly
mentioned in the literature but no analyses have been
given hitherto.
state with a spin-splitting of ꢁ50 cmꢀ1, and identified
ꢀ
3
3
excited states of P and R symmetries, near 4300 and
16 000 cmꢀ1, respectively. The NiO pure rotation spec-
trum has been observed [13] and three independent
reports of negative ion photoelectron studies of NiOꢀ
have been published [14–16].
Because of their importance in many fields, from
materials science to interstellar chemistry, 3d transition
metal monoxides have been the subject of many exper-
imental [1–3] and theoretical studies [4–6]. While the
database for ground and excited electronic states is ex-
panding it remains far from complete. In the case of
nickel monoxide, its ground state and several low-lying
excited states have been characterized but observations
at energies beyond 20 000 cmꢀ1 are only qualitative.
The emission spectrum of NiO was first observed in
1945 in the infrared and visible by Rosen [7,8] who ar-
ranged the numerous bands into six systems, labeled I
through VI, and suggested vibrational assignments [9].
Investigations by Srdanov and Harris [10], by Fried-
In this Letter we present detailed observations on 25
vibronic bands of NiO whose upper state levels lie
between 19 600 and 23 400 cmꢀ1
.
2. Experimental procedure
The apparatus and methods used to observe spectra
of NiO were not fundamentally different from those of
recent experiments in our laboratory [17]. The NiO
molecules were produced in a standard laser vaporiza-
tion molecular beam source, following reaction of a la-
ser ablation nickel plasma with ꢁ5% O2 or NO doped in
helium. The nickel was in the form of a rotating and
translating rod, 5-mm in diameter ꢂ 30-mm, 99.9% pu-
rity, from Strem Chemicals. Excitation (LIF) spectra in
the range 410–510 nm were generated using a Nd:YAG
pumped dye laser (Lumonics HY600 and HD300) with
* Corresponding author. Fax: +1-250-721-7147.
E-mail address: balfour@uvvm.uvic.ca (W.J. Balfour).
1
Present address: Department of Chemistry, Grant MacEwan
College, Edmonton, AB, Canada T5J 5J5.
0009-2614/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.cplett.2003.12.089

240
W.J. Balfour et al. / Chemical Physics Letters 385 (2004) 239–243
Exalite 416 and Coumarin 440, 460, 480 and 500 dyes.
The fluorescence was collected through a Jobin-Yvon
H20 monochromator and converted to an electrical
signal by a Hamamatsu R106UH photomultiplier tube.
Opto-galvanic signals from an Fe/Ne hollow cathode
lamp, known features in NiH, NiC and C2 spectra, and
the atomic spectrum of vanadium were used to calibrate
internally the probe laser. The band positions reported
are expected to be accurate within ꢃ1 cmꢀ1. Peaks
separated by 0.1 cmꢀ1 at 500 nm were clearly resolved in
our spectra and this resolution was sufficient to enable
all low J lines in each band to be identified.
NiH and these observations are being investigated
further.
58NiO band heads are listed in Table 1. In most in-
stances they can be identified with bands listed previ-
ously [9] although, as observed by Friedman-Hill and
Field [11], some discrepancies in positions over [9]
measurements are noted. All the NiO bands show a
similar R–P rotational structure as may be seen in the
474.54 nm band in Fig. 2. In most instances an accom-
panying weaker 60NiO band of similar structure is dis-
cernible slightly to the red of the main band. The 58Ni/
60Ni natural abundance is 2.6/1.
The NiO LIF bands are red-degraded and dispersed
fluorescence (DF) spectra were obtained by fixing the
probe laser frequency at or near a strong R-head and
scanning the monochromator. The uncertainty in our
Rꢀotational combination differences for the ground
X3R ðX ¼ 0þÞ, v ¼ 0 level were available [10,11] mak-
ing analysis straightforward. Within the precision of our
measurements, all NiO bands studied gave matching
lower state combination differences. Because data from
the jet-cooled source rarely gave measurable lines for
J > 15, the rotational lines were fitted, band by band,
using least squares to determine only a band origin m0
and DB ¼ B0 ꢀ B00. A fitting of published data for the 0þ
measurement of DF intervals is of the order of 15 cmꢀ1
.
3. LIF results
ꢀ
00
An overview of the spectrum, obtained by co-adding
many separate scans, is shown in Fig. 1. Between 400
and 480 nm, a mixture of Ni + CH4/He was used so that
features due to NiC and NiH can be seen. The NiC
observations are in perfect agreement with spectra re-
corded using resonant two-photon ionization spectros-
copy [18]. A weak band, with head at 434.97 and
m0 ¼ 22980 cmꢀ1, lies 869 cmꢀ1 lower in energy than
Brugh and MorseÕs NiC [23.8]X ¼ 0þ ꢀ X1Rþ0–0 band
and is clearly the accompanying 0–1 band. The
B2D5=2 ꢀ X2D5=2 system of NiH [19] was observed
strongly when either CH4/He or H2/He gas mixtures
were used. Features near 448 nm may also arise from
component of X3R gave B ¼ 0:474882 cmꢀ1. These
eff
parameters, together with the isotope shifts m0(58NiO)–
m0(60NiO), are included in Table 1. Table 2 lists rota-
tional assignments for the 479.08 and 474.54 nm bands.
Similar data for other bands are available on request
(WJB).
Experimental conditions and rotational analyses
confirm that all save perhaps the weakest features of our
NiO spectrum have the X3Rꢀ (X ¼ 0þ), v ¼ 0 level as
the lower level. The vibronic assignments suggested in
[9] then require substantial revision. Unfortunately, de-
spite the details from isotopic shifts and rotational
constants provided by the present study, a comprehen-
sive classification of bands is far from obvious. The
conclusion is that perturbations between excited states
are widespread.
A focus on position and isotopic shift suggests three
groupings of bands: (i) a progression from 479.08 nm,
namely bands at 479.08, 466.85, 455.29, 443.79 and
433.02 nm. Their corresponding isotopic shifts are 7.49,
7.65, 9.61, 16.7 (doubtful) and 10.50 cmꢀ1, and consec-
utive intervals of 547, 544, 568, and 562 cmꢀ1 represent
plausible vibrational spacings. This series had been
identified by Rosen [8] as a v ꢀ 1 progression; (ii) a
progression from 474.54 nm, namely bands at 474.54,
461.77, 449.63, and 438.05 nm, showing isotopic shifts of
7.28, 7.38, 9.3, and 12.2 cmꢀ1, respectively. These bands
occur at intervals of approximately 585 cmꢀ1; and (iii) a
progression from 466.22, namely bands at 466.22,
453.26, 441.14, and 430.24 nm, with corresponding iso-
topic shifts of 6.94, 9.03, 10.1, and 11.52 cmꢀ1. Here the
vibrational intervals are progressively 613, 606, and 573
cmꢀ1. The magnitudes of the isotopic shifts in all three
series suggest reasonably high upper level v quantum
numbers, e.g. v0 P 3 for the 479.08 nm band. However, in
Fig. 1. Low resolution survey LIF spectra. The upper spectrum, while
obtained with Ni + CH4/He, contains NiO bands due to small traces of
O2. The lower spectrum was recorded using Ni + O2/He. These spectra
show data collected under differing conditions and using a range of
laser dyes. Consequently relative intensities are only approximate.

W.J. Balfour et al. / Chemical Physics Letters 385 (2004) 239–243
241
Table 1
NiO band heads (nm), rotational constants (cmꢀ1) and 58NiO–60NiO isotopic shifts (cmꢀ1) observed in LIF between 420 and 510 nma
khead
(nm)
m0
(cmꢀ1
B0
(cmꢀ1
B0–B00
(cmꢀ1
Dmi0
(cmꢀ1
)
)
)
)
509.85
506.46
502.48
502.00
501.45
500.57
499.24
497.76
495.19
493.75
488.83
487.60
485.93b
479.08
474.54
471.14
466.85
466.22
461.77
461.01
455.29
453.26
449.63
443.79
441.14
438.54
438.05
433.02
430.62
430.24
427.93
19604.9
19736.2
19891
0.41762
0.40529
)0.06726
)0.06959
1.65
Very small
Very small
19912
19933
9.5?
19968
20021.6
20082
0.41782
–
)0.05706
–
2.24
9.3
20185.0
20245.1
20448.5
20500
0.40100
0.38582
0.40989
)0.07388
)0.08906
)0.06499
1.33
8.52
3.20
20570.8
20865.0
21064.5
21217
0.40878
0.40090
0.40574
)0.06610
)0.07398
)0.06914
4.82
7.49
7.28
11.3
7.65
6.94?
7.38
–
21411.9
21440.7
21646.5
21683.4
21955.5
22053.9
22231.4
22523.5
22659.9
22793.9
22819.2
23085.3
23213.9
23233.1
23359.5
–
–
0.40191
0.40692
–
)0.07297
)0.06796
–
0.40841
0.39239
0.40827
0.42433
0.39165
–
)0.06647
)0.08249
)0.06661
)0.05055
)0.08717
–
9.61
9.03
9.3
16.7?
10.1
–
0.37232
0.38913
0.38285
0.38909
0.38684
)0.10256
)0.08575
)0.09203
)0.08579
)0.08804
12.2
10.50
9.8
11.52
a B00 was fixed at 0.474882 cmꢀ1 (see text).
b Not certain that NiO X3Rꢀ(0þ) is the lower state.
NiO bands of Table 1 remain speculative at best. The
following groupings have separations of 550–600 cmꢀ1
517.45 nm (19 326 cmꢀ1) [10], 502.48 nm (19 891 cmꢀ1
and 488.83 nm (20 449 cmꢀ1); 509.85 nm (19 605 cmꢀ1
:
)
)
and 495.19 nm (20 185 cmꢀ1); and 438.54 nm (22 794
cmꢀ1) and 427.93 nm (23 360 cmꢀ1).
Three features in the Ni + CH4 spectrum show a
common but very different profile from the R-headed,
rotationally resolved bands of NiO and NiC. These
three features lie centered at 418.06, 425.65 and 437.35
nm. The latter two are seen in Fig. 1. They show the
high density of lines typical of a polyatomic species. Ni–
CH3 is a possibility. Similar observations have been
made using Fe + CH4 and Cr + CH4 [20]. Better spectra
than currently obtained are needed before a definite
identification of the carrier can be made.
Fig. 2. The LIF spectrum of NiO near 474.6 nm. The 58NiO and 60NiO
band centers are separated by 7.28 cmꢀ1
.
4. Dispersed fluorescence results
none of the series are lower energy members evident. The
question of upper level v numbering has been probed
further using DF (vide infra). Correlations among other
In two of the progressions identified above, the lead
bands, specifically those at 479.08 and 474.54 nm, are

242
W.J. Balfour et al. / Chemical Physics Letters 385 (2004) 239–243
Table 2
Rotational assignments (cmꢀ1) in the 479.08 and 474.54 nm bands of 58NiO and 60NiO
58NiO
60NiO
J
RðJÞ
PðJÞ
RðJÞ
PðJÞ
(a) 479.08 nm band
0
1
20 865.77 ()0.03)
866.47 (0.02)
866.86 ()0.09)
867.29 ()0.02)
867.51 (0.00)
867.60 (0.03)
867.521 (0.05)
867.29 (0.08)
866.73 ()0.06)
866.21 ()0.01)
865.51 (0.03)
864.61 (0.04)
863.55 (0.06)
862.29 (0.06)
860.90 (0.10)
–
20 864.03 (0.01)
862.94 ()0.01)
861.73 (0.03)
20 856.55 (0.00)
855.42 ()0.04)
854.20 ()0.02)
852.94 (0.12)
851.24 ()0.04)
849.59 (0.02)
847.72 (0.00)
845.64 ()0.07)
843.47 ()0.06)
841.21 (0.02)
838.69 (0.00)
836.09 (0.08)
2
20 859.42 (0.00)
859.77 (0.00)
859.98 (0.02)
859.98 ()0.02)
3
4
860.29 ()0.01)
858.72 ()0.04)
857.07 (0.01)
5
6
7
855.24 (0.04)
8
853.16 ()0.03)
850.98 ()0.04)
848.64 ()0.05)
846.16 ()0.01)
843.51 ()0.02)
840.64 ()0.06)
837.65 ()0.03)
834.39 ()0.09)
831.01 ()0.09)
9
10
11
12
13
14
15
16
(b) 474.54 nm band
0
1
21 065.27 (0.04)
065.93 (0.03)
066.47 (0.04)
066.82 ()0.01)
067.04 ()0.04)
067.13 ()0.07)
067.13 ()0.04)
067.04 (0.04)
066.69 (0.01)
066.20 (0.00)
065.58 (0.01)
064.74 ()0.03)
063.85 (0.04)
062.70 (0.03)
061.36 (0.01)
059.81 ()0.03)
–
21 063.49 (0.00)
062.43 (0.01)
061.23 (0.03)
059.81 ()0.04)
058.35 (0.00)
056.71 (0.00)
054.89 ()0.02)
052.94 ()0.03)
050.86 ()0.01)
048.64 (0.04)
046.16 (0.00)
043.55 (0.00)
21 056.27 (0.03)
055.07 ()0.08)
053.87 ()0.06)
052.59 (0.03)
051.04 ()0.02)
049.40 (0.00)
047.63 (0.03)
045.68 (0.03)
043.55 (0.00)
041.25 ()0.04)
2
21 059.24 (0.07)
059.59 (0.04)
059.81 (0.03)
059.81 ()0.07)
059.81 ()0.01)
059.59 ()0.03)
059.24 ()0.02)
058.75 (0.01)
058.08 (0.01)
057.29 (0.06)
056.18 ()0.04)
055.07 (0.03)
3
4
5
6
7
8
9
10
11
12
13
14
15
the strongest members. DF spectra were recorded with
probe laser excitation fixed to coincide with the most
intense R-head region in the 58NiO isotopomer of each
band. Excitation at 479.080 nm gave the DF spectrum
shown in Fig. 3. At 474.714 nm, the result was quali-
tatively similar. Both DF spectra are readily interpreted
in terms of emission solely into the vibrational manifold
of the electronic ground state, v ¼ 0–9. Somewhat sur-
prisingly we find no sign of the low-lying electronic
levels near 2525, 3910, 4325 and 5225 cmꢀ1 present in
the negative ion photoelectron spectra of NiO [14–16].
Measured vibrational energies are given in Table 3.
Also included in Table 3, for comparison, are level
predictions based on the xe ¼ 839:1 cmꢀ1 and
xexe ¼ 5:4 cmꢀ1 vibrational constants of Srdanov and
Harris [10] determined from v ¼ 0, 1 and 2 data. Since
agreement between the two set of data is excellent a
dissociation energy given by x2e=4xexe ¼ 32600 cmꢀ1
may be reasonable.
Fig. 3. The dispersed fluorescence spectrum of 58NiO obtained using a
probe laser wavelength of 479.080 nm.

W.J. Balfour et al. / Chemical Physics Letters 385 (2004) 239–243
243
Table 3
Ground state 58NiO vibrational levels (cmꢀ1) observed in dispersed
fluorescence at two excitation wavelengths
Acknowledgements
The authors wish to thank Dr. M.D. Morse (Utah)
for a copy of his paper on NiC prior to publication and
Dr. R.W. Field (MIT) for helpful correspondence. This
research was supported by funding from the University
of Victoria and the Natural Sciences and Engineering
Research Council of Canada.
v
kexc at 479.080 nm
kexc at 474.714 nm
From [10]
0
1
2
3
4
5
6
7
8
9
0
830
0
820
0
828
1645
2460
3255
4030
4810
5575
6325
7070
1635
2440
3240
1646
2453
3248
4034
4808
5571
6324
7066
4795
5560
References
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the excited state and the estimated parameters x0e ¼ 548
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5. Conclusions
The jet-cooled electronic spectrum of NiO has been
studied between 410 and 510 nm where twenty bands
have been observed and rotationally analyzed. Earlier
vibronic assignments have had to be revised, m0(58NiO)–
m0(60NiO) isotopic shifts have been measured and ten-
tative new assignments of several upper state vibrational
progressions are suggested. Dispersed fluorescence
spectra map ground state vibrational levels up to v ¼ 9.
[15] V.D. Moravec, C.C. Jarrold, J. Chem. Phys. 108 (1998) 1804.
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(2003) 106.
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[19] A. Heimer, Doctoral Dissertation, University of Stockholm, 1937.
[20] W.J. Balfour, J. Cao, R.H. Jensen, unpublished.