Laser ablation molecular isotopic spectrometry (LAMIS) involves measuring isotope-resolved molecular emission. Measurements of several key isotopes (hydrogen, boron, carbon, nitrogen, oxygen, and chlorine) in laser ablation plumes were demonstrated. Requirements for spectral resolution of the optical detection system could be significantly relaxed when the isotopic ratio was determined using chemometric regression models. Multiple applications of LAMIS are anticipated in the nuclear power industry, medical diagnostics and therapies, forensics, carbon sequestration, and agronomy studies.

1. 30 Spectroscopy 29(6) June 2014 www.spectroscopyonline.com
Laser ablation molecular isotopic spectrometry (LAMIS)
is a technique that uses optical spectra of transient mo-
lecular species produced in ablation plumes in air or buf-
fer gases (Ar, Ne, He, and N2) for rapid isotopic analysis of
solid samples (1–8). This technique is similar to laser-induced
breakdown spectroscopy (LIBS), but optical emission spectra
in LAMIS are measured at longer delays after an ablation
pulse than what is used in LIBS. Molecular emissions yield
relatively easily detectable isotopic information. Therefore,
LAMIS adds a supplementary function of isotopic measure-
ments to the well-established benefits of LIBS (real-time el-
emental analysis at atmospheric pressure, minimal sample
preparation, chemical mapping and depth profiling at high
spatial definition, and laboratory and field operation possible
at a standoff distance to the sample). The LIBS and LAMIS
techniques can be accomplished on the same instrument.
Molecular radicals are generated effectively when the
ablation plume cools down, resulting in an increase of the
molecular emission in the plasma afterglow. Several mecha-
nisms contribute to the formation of molecules in the plume
such as radiative association of neutral atoms, associative
excitation or ionization, recombination of molecular ions,
fragmentation of polyatomic clusters or nanoparticles, and
vaporization of intact molecules from the ablated surface.
Molecular spectra are advantageous for isotopic analysis be-
cause the isotopic shifts in molecular emission are consider-
ably larger than in atomic spectra. The difference in isotopic
masses has only a small effect on electronic transitions in
atoms, but significantly affects the vibrational and rotational
energy levels in molecules (1). A compact spectrometer can
be sufficient to resolve molecular isotopic spectra, therefore
LAMIS measurements can be performed in the field (4,5).
The ability to measure isotope abundance using a portable
spectrometer with modest spectral resolution is a significant
merit of LAMIS, along with no sample preparation and data
collection at ambient pressure.
The qualitative and quantitative studies of isotopes of the
light elements are both very important for their use in many
fields and for their very extensive scope, with many appli-
cations in different fields of their chemistries and materials
science. This article describes measurements of isotopes of
hydrogen, boron, carbon, nitrogen, oxygen, and chlorine.
All of these elements are ubiquitous in nature as well as in
practice, with carbon being the basis of many millions of
compounds. Variation of the natural isotopic ratio 13C/12C
in different materials ranges from 0.96% to 1.15% (9). These
variations can be measured using LAMIS. Fractionation in
stable isotopes of C, N, and O can be particularly indicative of
a range of diverse biotic and abiotic processes relevant to the
ecology, biosphere, and geochemistry, both organic (fossil)
and inorganic. Fertilizers enriched typically above 40% in
15N relative to 14N are broadly used to track the efficiency of
plant uptakes, fertilizer losses, and nitrogen turnover in soil.
High neutron absorbing capacity of the 10B isotope led
to the development of multiple boron-loaded materials for
neutron shielding in nuclear reactors and spent fuel storage
pools, as well as for screens and curtains in nuclear medicine
centers. Enrichment from 50% up to 99% in 10B relative to
Alexander A. Bol’shakov, Xianglei Mao, Dale L. Perry, and Richard E. Russo
Laser ablation molecular isotopic spectrometry (LAMIS) involves measuring isotope-resolved
molecular emission. Measurements of several key isotopes (hydrogen, boron, carbon, nitrogen,
oxygen, and chlorine) in laser ablation plumes were demonstrated. Requirements for spectral
resolution of the optical detection system could be significantly relaxed when the isotopic ratio
was determined using chemometric regression models. Multiple applications of LAMIS are
anticipated in the nuclear power industry, medical diagnostics and therapies, forensics, carbon
sequestration, and agronomy studies.
Laser Ablation Molecular Isotopic
Spectrometry for Rare Isotopes
of the Light Elements

2. 32 Spectroscopy 29(6) June 2014 www.spectroscopyonline.com
11B is often used. Many neutron detec-
tion devices are also based on highly
borated (10B) and deuterated (2H) scin-
tillator materials. Heavy water nuclear
reactors require deuterium enrichment
to 99.85%. Water-18O is used as a pre-
cursor in the radiopharmaceutical
industry. Deuterated drugs and stable
isotopic markers are increasingly used
in the fields of medicine, pharmacology,
nutrition, and physiology for tracing
biochemical processes. Medical mul-
tinuclear magnetic resonance imaging
(MRI) scanners require compounds en-
riched in nuclear magnetic resonance
(NMR)-active isotopes (13C, 15N, and
17O). To assess quality, specifications,
or aging of these materials, their iso-
topic homogeneity or distribution, and
degree of isotopic enrichment can be
rapidly tested by LAMIS in open air
or inert gas flush without using labori-
ous and expensive mass spectrometry
(MS). The feasibility of standoff LAMIS
analysis is particularly important for
the nuclear industry.
Natural geochemical heterogene-
ity in isotopic composition reflects the
complex history of our planet. Isotopic
ratios of B, C, O, and Cl are particularly
variable in nature because of chemical
reactivity, high solubility, and volatility
associated with the compounds con-
sisting of these elements. Boron and
chlorine isotopic fractionation is used
to trace the records of evolution and
weathering reactions because of interac-
tions of rocks, soil, and sediment mate-
rials with water. Biomediated alteration
of the 37Cl/35Cl ratio is distinctive in mi-
crobial reduction of anthropogenic per-
chlorates, biphenyls, freons, and other
chlorinated compounds. Simultaneous
measurement of multiple stable isotopes
is also increasingly used to constrain
the carbon cycling in ecosystems bet-
ter. LAMIS can facilitate the isotopic
analysis directly in the field. Numerous
applications of LAMIS are anticipated
in the nuclear power industry, medical
diagnostics and therapies, forensics,
carbon sequestration, and agronomy
studies.
Experimental
A flash-lamp pumped Nd:YAG laser
operating at 1064 nm with a pulse
energy of 50–150 mJ and a pulse du-
ration of 4 ns was used to ablate the
samples. The laser beam was focused
onto the sample with a fused-silica lens
to a spot diameter of ~100 μm, either
in open air or in a cylindrical quartz
200
150
100
50
0
Emissionintensity
Wavelength (nm)
592 594 596 598 600 602 604 606
Figure 1: Isotope-specific molecular spectra of BO (A→X; 0-3) emission formed during ablation
of two aluminum-based composite materials containing different 11B/10B ratios. The upper
spectrum (BorAluminum) is shifted up for clarity. Lower spectrum: Boral.
100
80
60
40
20
Emissionintensity
Wavelength (nm)
12
C14
N+13
C14
N
12
C15
N
13
C14
N
13
C14
N
13
C14
N
12
C15
N
12
C15
N
12
C14
N
12
C14
N
415 416 417 418 419 420 421 422
Figure 2: Emission spectra of CN vibrational band progression (B→X; Δν = +1) formed during ablation
of benzamide pellets enriched in 13C and 15N isotopes. Spectra were averaged over 100 laser pulses.

3. June 2014 Spectroscopy 29(6) 33www.spectroscopyonline.com
chamber flushed with inert gas. Inert
gas flow removed ambient air when the
rare isotopes of nitrogen and oxygen
were to be measured. A second lens
was used to collect the laser-induced
plasma emission in the direction per-
pendicular to the ablating laser beam.
Two spectrometric configurations were
interchangeably used. In one of them,
collected light was focused onto a fiber-
optic cable coupled to a compact echelle
spectrograph (EMU-65, Catalina Scien-
tific) fitted with an electron multiplying
charge-coupled device (EMCCD). In
the other configuration, collected light
was focused onto the entrance slit of a
Czerny-Turner spectrograph fitted with
an intensified charge-coupled device
(ICCD). The spectrum acquisition gate
widths and delays were optimized to
detect molecular emission, while mini-
mizing intensity of atomic and contin-
uum radiation. The collected spectra
were averaged over several tens or hun-
dreds of laser shots (see further text and
notes in the figure captions). The spec-
tral averaging, background correction,
normalization, and final chemometric
regression analysis of spectral data were
performed using proprietary software
designed at Applied Spectra for multi-
variate calibration and quantification of
LIBS spectra.
Substances with known isotopic
content were obtained from commer-
cial sources in the form of powder,
then mixed in appropriate proportions
and pressed by a 7-ton press into 1-cm-
diameter pellets. Isotopically enriched
water was frozen into ice tables, which
were kept cold by a Peltier thermoelec-
tric plate during ablation for the LAMIS
analysis. Samples of borated aluminum
materials were provided by Ceradyne,
Inc.
Results and Discussion
Our previous measurements of boron
isotopes 10B and 11B were performed
using three chemically pure substances,
isotope-enriched 10B2O3, 11B2O3, and
natural BN (2,7). The results indicated
that LAMIS can be calibrated using
multivariate partial least squares regres-
sion (PLSR) for quantitative measure-
ments of isotopic ratio with high pre-
cision represented by relative standard
deviation of only ±0.45% (2σ = 9‰),
and this can be further improved (7).
Abundances of individual isotopes in
material composition can be measured
at least down to ~1% (13C and 15N can be
detected in subnatural concentrations,
below 0.3%). High spectral resolution
was found unnecessary for isotopic de-
termination (2). However, an ambiguity
remained about whether similar results
could be obtained on practical samples
with possible spectral interferences
from other chemical elements.
The pertinence of LAMIS measure-
ments to industrial applications was
tested on neutron absorber materials.
Two samples of aluminum alloyed
composites with different boron isotope
ratios were ablated and analyzed using
a 320-mm IsoPlane spectrograph fitted
with a PI-MAX4 ICCD detector (Acton/
Princeton Instruments). One of these
samples was a Boral core (Ceradyne)
that consolidated aluminum alloy with
56% boron carbide of natural boron iso-
tope abundance. The other sample was

4. 34 Spectroscopy 29(6) June 2014 www.spectroscopyonline.com
BorAluminum (Ceradyne), a regular
unalloyed aluminum (grade 1100) with
4.5% added elemental boron, enriched
in the lighter isotope 10B up to 95%.
The ablation spectra of these samples
recorded in the 591–608 nm spectral in-
terval are presented in Figure 1 (contin-
uum background subtracted). They are
different because the isotopic composi-
tion is different. These spectra belong to
moderately resolved rotational lines of
boron monoxide in the vibrational band
(0-3) of the A2Πi→X2Σ+ emission sys-
tem. The spectra were acquired using
a 1800-grooves/mm (gr/mm) grating
with the ICCD delay of 10 µs and a gate
width of 100 µs. Spectral intensity was
accumulated over 1000 laser pulses
(analysis time 100 s at 10 Hz).
In previous work on LAMIS, the BO
A2Πi→X2Σ+ emission was used at both
the (0-2) band (4,7) and the (0-3) band
(2,7,10). A choice of the spectral interval
was driven by quality of the spectra for
multivariate quantification with dif-
ferent chemometric procedures. The
data in Figure 1 illustrate a significant
isotopic shift between spectra of Boral
(80% 11B) and BorAluminum (95% 10B),
requiring only modest spectral resolu-
tion. Another important factor is that
this spectral interval does not have any
visible interferences from atomic alumi-
num or chemical impurities in the sam-
ples. When the ablation spectrum was
recorded at the usual acquisition delays
for LIBS (<1 µs), several spectral lines
of Fe, Ti, and Mn atoms coming from
impurities in borated aluminum were
observed within this range. Provided
that the interfering lines are sparse, they
do not necessarily preclude the isotopic
analyses. Thus, time-gated attenuation
of atomic emission is deemed essential
for LAMIS measurements in practical
analyses.
A possibility of LAMIS applications
for geological analysis was examined
using two tourmaline samples of dif-
ferent color (greenish “blue grass”
and black minerals). The regular LIBS
spectra of these samples indicated that
a spectral region from 572 to 585 nm
had the least amount of atomic inter-
ferences. Aimed at further decreas-
ing atomic emission, the acquisition
gate delay was set at 3 µs for LAMIS
measurements. However, two spectral
lines of atomic iron were persistent in
the spectrum of one of the tourmaline
samples. The positions of these inter-
fering lines could be masked from the
spectrum to determine the isotopic
composition using multivariate PLSR
described in the literature (2,7). Fur-
ther quantitative work is needed to de-
termine the limits of isotopic precision
and sensitivity in LAMIS of geological
samples. However, measuring boron
100
80
60
40
20
0
Emissionintensity
Wavelength (nm)
355 356 357 358 359 360 361
12 14
12 15
13 14
Figure 3: CN vibrational bands (B→X; Δν = –1) formed during ablation of natural graphite and
enriched benzamide pellets. Spectra were averaged over 100 laser pulses.
10
9
8
7
6
5
4
3
2
1
0
1.5
1.0
0.5
0.5 1.0 2.01.5
Calculated13
Ccontent(%)
Calculated13
Ccontent(%)
Nominal 13
C content (%)
Predicted 13
C
Linear fit
Confidence
Natural
0 1 2 3 4 5 6 7 8 9 10
Figure 4: Calibration plot with a linear fit and 95% confidence interval for the 13C isotopic content
calculated using the PLSR model.

5. June 2014 Spectroscopy 29(6) 35www.spectroscopyonline.com
isotopes in real geological samples using
LAMIS has already been established as
a credible prospect. Our previously at-
tained precision of 9‰ (7) is reasonably
adequate because natural variation of
the 10B/11B ratio in the terrestrial envi-
ronment is more than 90‰ (9).
The ability to measure the 10B and
11B content by LAMIS will be useful
in other applications. For instance, the
11B isotope is added to semiconductor
grade silicon as a doping agent that
must be controlled. LAMIS can monitor
nuclear facilities remotely, delivering a
laser beam through a small window and
collecting optical emission either by a
telescope or an optical fiber cable.
Carbon and nitrogen isotopes can
be determined simultaneously using
spectra of CN molecules in LAMIS
measurements. This possibility was
briefly mentioned in our earlier publi-
cations (1,4,5). The carbon isotope 13C
is the most important one for studying
biochemistry, but measuring only one
isotope is often insufficient. Several
key isotopes can follow the biologi-
cal processes better. To demonstrate
simultaneous isotopic measurements,
we ablated natural graphite and several
solid substances enriched in 13C and
15N. The spectra presented in Figure 2
include the B2Σ+→X2Σ+ vibrational band
progression: (0-1), (1-2), (2-3), (3-4) of
the CN radical. The rotational structure
of these bands is barely resolved in our
measurements, but isotopic shifts be-
tween isotopologues of 12C14N, 13C14N,
and 12C15N are clearly observed. Two
pellets of isotope-enriched benzamide
with 13C and 15N atomic fractions 14%
and 99%, respectively, were used as ab-
lation targets. The latter was ablated
in a helium flow to preclude nitrogen
entrainment from air. Another sample
was 99% enriched with 13C amorphous
carbon. The spectra were acquired
using a 10-µs timing gate delayed after
the laser pulse only by 1.5 µs because
CN molecules are promptly formed in
laser ablation.
Isotopic shifts in the bands with
changing vibrational quantum number
Δν = +1 shown in Figure 2 are all larger
than 0.3 nm and are easily resolvable
using a compact optical spectrograph.
These shifts are about 10 times greater
than the isotopic shift in the (0-0) band
head of the same CN B2Σ+→X2Σ+ tran-
sition at ~388 nm (1). The opposite
change in a vibrational quantum num-
ber Δν = –1 produces another CN band
progression around 359 nm (Figure 3).
The isotopic differences in these bands
are well resolved, but their rotational
structure is not. An advantage of using
the bands (1-0), (2-1), and (3-2) near
359 nm shown in Figure 3 compared to
those shown in Figure 2 is that the spec-
tral peaks with Δν = –1 attributed to the
minor isotopes 13C and 15N occur aside
the sharp edge of the 12C14N (1-0) band
head. This is important for quantitative
calibration. The progression with Δν =
+1 requires multivariate calibration
because the bands from minor isotopes
can be hidden within unresolved rota-
tional lines of the major 12C14N bands.
In contrast, spectral data of the progres-
sion with Δν = –1 can be quantified
using either univariate or multivariate
calibration.
The results of calibrating LAMIS

6. 36 Spectroscopy 29(6) June 2014 www.spectroscopyonline.com
spectra of a CN molecule using a multi-
variate PLSR procedure for quantitative
determination of 13C content in solid
organic samples are presented in Figure
4. Artificial reference samples were pre-
pared by physically blending powders
of natural and 13C-enriched decanoic
acid. A natural 13C atomic fraction was
assumed as 1.07%, and an additional
five blended samples were made nomi-
nally at 1.2%, 1.5%, 2.0%, 5.0%, and
9.9%. The CN B→X (Δν = –1) spectra
were collected in the interval 353–362
nm, similar to those shown Figure 3.
The error bars in Figure 4 correspond
to standard deviation of a single mea-
surement within 10 replicates, while
each measurement was made by accu-
mulating spectra from 100 laser pulses.
The natural 13C atomic fraction was
recalculated from these measurements
as 1.09 ± 0.14%. Averaging over 10 mea-
surements (each one made of 100-pulse
accumulations) reduces a random error
of the average down to ±0.044%. It is
obvious from data presented in Figure
4 that LAMIS can measure subnatu-
ral abundances of 13C with sufficient
precision. However, the decanoic acid
powders used to prepare our reference
samples consisted of microcrystals and
it was difficult to fully homogenize a
blended material. Better homogenized
standards will improve precision and
accuracy of LAMIS measurements.
We tested LAMIS in analyzing the
soil samples, in which the total carbon
content was 12.26%, and the nitrogen
content was 0.27%. For initial experi-
ments, we spiked this soil with 15N-
enriched benzamide and 13C-enriched
decanoic acid in different proportions.
Several spectral lines of iron appear as
interferences in the region of CN B→X
Δν = –1) bands, but iron lines were
well resolved from carbon features.
An algorithm that automatically fits
a Lorentzian profile to every interfer-
ing spectral line and digitally subtracts
them from the spectrum can be applied
as a remedy. Such a procedure can work
relatively well if the interfering lines are
no more than three times stronger than
the main spectrum.
A similar multivariate PLSR calibra-
tion was performed for measurements
of the 15N isotope using reference sam-
ples prepared by blending powders of
natural and 15N-enriched benzamide.
The 15N atomic fractions in prepared
reference samples were 0.37%, 1.0%,
2.0%, 5.0%, 10%, 20%, and 99%. In
these experiments, the CN B→X (Δν
= +1) spectra were collected within the
range 414–422 nm, similar to those
shown Figure 2. The results are dis-
played in Figure 5 with the error bars
corresponding to standard deviation
of a single measurement, each made
100
90
80
70
60
50
40
30
20
10
0
Calculated15
Ncontent(%)
Nominal 15
N content (%)
0 10 20 30 40 50 60 70 80 90 100
15
10
5
0
Calculated15
Ncontent(%)
0 5 10 15 20
Predicted 15
N
Linear fit
Confidence
Figure 5: Calibration plot with a linear fit and 95% confidence interval for the 15N isotopic content
calculated using the PLSR model.
40
30
20
10
0
Emissionintensity
Wavelength (nm)
312.0 312.3 312.6 312.9 313.2 313.5 313.8
16
18
16
Figure 6: Spectra of 16OH, 18OH, and 16OD molecules in the A→X (0-0) band formed during laser
ablation of ice. Spectra were averaged over a series of 10 replicates, each made of 100-pulse
accumulations.

7. June 2014 Spectroscopy 29(6) 37www.spectroscopyonline.com
by signal accumulation from 100 laser
pulses. Again, quantification preci-
sion and accuracy were limited by mi-
croscale isotopic inhomogeneity of the
reference samples that were prepared.
Inaccuracies in preparing these refer-
ence mixtures to be equal to the nomi-
nal isotopic content also increased the
calibration errors.
During laser ablation of carbon-
containing samples, both CN and C2
radicals are often generated in compa-
rable quantities. Hence, both of these
species can be used for measuring the
carbon isotopic ratio. Utilization of di-
atomic carbon molecules C2 for LAMIS
measurements was described previously
(1,5,8). Rapid spatial and temporal evo-
lution of the plasma plumes during laser
ablation may cause kinetic fractionation
effects altering stoichiometric and iso-
topic equilibrium between the plasma
and the sample. Kinetic isotope frac-
tionation was indeed observed at early
stages of plume evolution (gate delays
<2 μs) in C2 emission (8). At longer de-
lays, the measured isotopic ratio was
close to the real ratio in the sample.
These results suggest that carbon iso-
topes 12C and 13C can behave differently
in laser ablation plumes, and the change
in ratio is related to the time and spa-
tial distance above the sample. For the
purpose of isotopic analysis, it is impor-
tant that the isotopic ratio measured at
longer delays (>2 μs) equilibrates and
approaches the real ratio in the sample
roughly at the same time when molecu-
lar emission is also reaching its maxi-
mum.
To demonstrate LAMIS for hydro-
gen and oxygen isotopic measure-
ments, we ablated ordinary water ice
(H2O), heavy water ice (D2O), and ice
with 90% atomic fraction of 18O. As in
earlier work (1,6), we recorded emission
of hydroxyl radicals at the A2Σ+→X2Πi
(0-0) transition in the ablation plumes.
The major features of OH emission
are R11 and R22 branch heads near 306
nm, the Q11 branch head at ~308 nm,
and the Q22 branch head at ~309 nm.
These rotational branch heads are suit-
able for the D/H ratio determination
because the isotopic shifts between OH
and OD features are large and can be
measured at low resolution. However,
isotopic shifts between 16OH and 18OH
are smaller, especially for the lines with
low rotational quantum numbers. The
isotopic shifts increase with increasing
quantum numbers in the band tails.
The hydroxyl isotopologue spectra
recorded in wavelength region 311.8–
314.0 nm using an IsoPlane spectro-
graph (Princeton Instruments) with a
3600-gr/mm grating are presented in
Figure 6. The ICCD gate duration was
50 µs and delayed 5 µs after the laser
pulse. Argon flow was applied to dis-
place air. The most intense features
contributing to the shown spectra be-
long to OH rotational lines of Q11 and
Q22 branches with quantum numbers
from J = 13.5 to J = 18.5. Smaller con-
tributions come from P11, P22, and other
minor branches of the (0-0) band, and
also from the second vibrational band
(1-1). These results demonstrate that hy-
drogen and oxygen isotopes can be de-
termined simultaneously using spectra
of hydroxyl isotopologues 16OH, 18OH,
and 16OD recorded with a compact

8. 38 Spectroscopy 29(6) June 2014 www.spectroscopyonline.com
spectrograph. Quantitative isotopic
calibration for ice analysis can be ac-
complished using multivariate PLSR as
previously realized for water vapor (6).
Isotopic analysis of ice is the main
tool in paleoclimatology and glaciology
studies, but measuring 18O/16O ratios in
rocks and minerals is important for geo-
chemists as well. Aluminum oxide is a
common constituent in many minerals.
As a result, molecular spectra of AlO
are easily detectable in laser ablation of
rocks. We observed five band progres-
sions of AlO B2Σ+→X2Σ+ (Δν = 0,±1,
±2) emission within a broad interval
445–545 nm from several rocks includ-
ing feldspar, tourmaline, and rock salt.
However, this spectral range is generally
contaminated by many other spectral
lines, and each particular experiment
will require choosing a smaller specific
segment of the spectrum. We ablated
natural and isotope-enriched Al2O3
pellets, flushed with helium flow to
illustrate that Al18O and Al16O can be
resolved in LAMIS. The spectra of AlO
B→X (Δν = +1) are presented in Figure
7, indicating that AlO emission can be
used to measure the oxygen isotopic
ratio 18O/16O in rock samples.
Calcium oxide is another common
constituent of rocks and minerals. Sev-
eral emission bands of CaO A1Σ+→X1Σ+
(2-0, 1-0, 0-0, 0-1) were clearly observed
within 765–960 nm during ablation of
calcite (CaCO3) and calcium chloride
(CaCl2) in air. Molecular structure and
spectrophysical properties of CaO are
similar to those of SrO. Emission of the
latter was previously used for LAMIS de-
tection of three strontium isotopes (88Sr,
87Sr, and 86Sr) (3–5). Our numerical sim-
ulation of the Ca18O and Ca16O spectra
predicted that CaO emission can be used
to infer oxygen isotopic information.
Additionally, laser ablation of CaCl2 pro-
duced emission of the CaCl B2Σ+→X2Σ+
band progression with Δν = –1. We re-
corded the spectra of CaCl B→X system
using two spectrographs, one of which
was 1250-mm Czerny-Turner spectro-
graph (Horiba JY) and the other one
was an echelle spectrograph EMU-65.
The results are displayed in Figure 8.
The natural isotopic ratio of chlorine
37Cl/35Cl is 24.2% to 75.8%, respectively.
The isotopic shifts because of these
two isotopes are apparent in the spec-
tra shown in Figure 8. While the large
high-resolution spectrograph recorded a
superior spectrum, the compact echelle
spectrograph yielded sufficient resolu-
tion for LAMIS measurements.
200
150
100
50
0
Emissionintensity
Wavelength (nm)
464 465 466 467 468 469 470 471 472 473 474 475 476
AI16
O+AI18
O
AI16
O
AI16
O
AI16
O
AI18
O
AI18
O
Figure 7:EmissionspectraofAlOvibrationalbandprogression(B→X;Δν =+1)formedduringablation
of Al2O3 natural and 18O-enriched pellets. Spectra were acquired with a 20-µs delay and averaged over
100 laser pulses.
150
100
50
Emissionintensity
Wavelength (nm)
579 580 581 582 583 584
35
37
Figure 8: Spectra of CaCl band progression (B→X; Δν = –1) formed during ablation of natural CaCl2
pellets. Spectra were acquired with a 20-µs delay and averaged over 20 laser pulses.

9. June 2014 Spectroscopy 29(6) 39www.spectroscopyonline.com
Conclusion
We demonstrated several possibili-
ties of using LAMIS for rapid optical
analysis of rare isotopes of hydrogen,
boron, carbon, nitrogen, oxygen, and
chlorine. A significant advantage of
this technique is that solid samples
can be analyzed in their original un-
altered condition, without preparation.
Precleaning of the sample surface can
be completed by laser ablation before
or during the analysis, which may be
considered as depth profiling. Isotopic
two- and three-dimensional mapping
is possible. Quantitative measure-
ments can be realized using multi-
variate regression models that will
relate the spectral intensities of the
isotope-specific molecular spectra to
the original abundances of isotopes
in the sample. Quantification is based
on measuring spectra of known refer-
ence samples. Calibrating the LAMIS
response for quantitative determina-
tion of C and N isotopes is presented
here, while calibration for H and B
isotopes was described earlier (2,6,7).
Accuracy and precision of determina-
tion depends on isotopic homogeneity
of the reference standards, but the ana-
lyzed samples can be heterogeneous.
LAMIS can yield a map of the isotopic
distribution.
References
(1) R.E. Russo, A.A. Bol’shakov, X. Mao, C.P.
McKay, D.L. Perry, and O. Sorkhabi, Spec-
trochim. Acta, Part B 66, 99–104 (2011).
(2) X. Mao, A.A. Bol’shakov, D.L. Perry, O. Sork-
habi, and R.E. Russo, Spectrochim. Acta, Part
B 66, 604–609 (2011).
(3) X. Mao, A.A. Bol’shakov, I. Choi, C.P. McKay,
D.L. Perry, O. Sorkhabi, and R.E. Russo, Spec-
trochim. Acta, Part B 66, 767–775 (2011).
(4) A.A. Bol’shakov, X. Mao, C.P. McKay, and
R.E. Russo, Proc. SPIE 8385, paper 83850C
(2012).
(5) A.A. Bol’shakov, NASA Tech Briefs, Photon-
ics, 36(11), Ia–3a (2012).
(6) A. Sarkar, X. Mao, G.C.-Y. Chan, V. Zorba,
and R.E. Russo, Spectrochim. Acta, Part B
88, 46–53 (2013).
(7) A. Sarkar, X. Mao, and R.E. Russo, Spectro-
chim. Acta, Part B 92, 42–50 (2014).
(8) M. Dong, X. Mao, J.J. Gonzalez, J. Lu, and R.E.
Russo, Anal. Chem. 85, 2899–2906 (2013).
(9) T.B. Coplen, J.A. Hopple, J.K. Böhlke et al., ,
US Geological Survey, Water-Resources In-
vestigations Report 01-4222 (2002).
(10) B. Yee, K.C. Hartig, P. Ko, J. McNutt, and I.
Jovanovic, Spectrochim. Acta, Part B 79–80,
72–76 (2013).
Alexander A. Bol’shakov is
with Applied Spectra, Inc., in Fremont,
California. Richard E. Russo is
with Applied Spectra, Inc., and the
Lawrence Berkeley National Laboratory
at the University of California in Berkeley,
California. Xianglei Mao and
Dale L. Perry are with the Lawrence
Berkeley National Laboratory at the
University of California. Direct correspon-
dence to: rerusso@lbl.gov ◾
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