# ToF-SIMS spectra of caffeic acid, vanillin, eugenol, and cellulose in positive polarity

Aline Cournut, Sarah Belhachmi, Caroline Bouvier, Alain Brunelle

► To cite this version:

Aline Cournut, Sarah Belhachmi, Caroline Bouvier, Alain Brunelle. ToF-SIMS spectra of caffeic acid, vanillin, eugenol, and cellulose in positive polarity. Surface Science Spectra, 2025, 10.1116/6.0004753. hal-05222389

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# ToF-SIMS spectra of caffeic acid, vanillin, eugenol, and cellulose in positive polarity

Aline Cournut¹, Sarah Belhachmi¹ᵃ), Caroline Bouvier¹ᵇ), Alain Brunelle¹ᶜ)

¹Laboratoire d'Analyse Moléculaire et Structurale, CNRS, Sorbonne Université, Paris, France

(Received day Month year; accepted day Month year; published day Month year)

Initially used for fermentation or storage, oak wood barrels were found to enhance the organoleptic properties of spirits. Over time, wood compounds have been linked to the quality of the spirits. ToF-SIMS being an ionization technique that produces intense fragmentation patterns which are not fully understood, reference spectra are required to confidently analyze wood samples. Here, positive polarity ToF-SIMS reference spectra of important oak wood compounds being involved in spirit maturation, using a Bi₃⁺ primary ion species, are presented.

**Keywords:** ToF-SIMS, standard, oak wood

Accession#: 02030, 02031, 02032, 02033

Technique: ToF-SIMS

Specimen: Caffeic acid, vanillin, eugenol, cellulose

Instrument: IONTOF, TOF-SIMS IV

Major Species in Spectra:
C, H, N, O

Minor Species in Spectra:
None

Published Spectra: 4

Spectral Category:
Reference

## INTRODUCTION

Initially used for fermentation or storage, oak wood barrels were discovered to enhance spirits organoleptic qualities. This realization highlighted the critical role of the barrel-making process. To manufacture high-quality barrels, the wood must have specific characteristics. It should be straight-grained, strong, and flexible enough to be bent. Moreover, the wood should be free from undesirable flavors. To do so, oak wood used for barrels undergoes several processing stages such as toasting. During the toasting process, significant chemical changes occur, breaking down chemical bonds between natural polymers (cellulose and lignin). Over time, the influence of wood compounds has been linked to the quality of the spirits.

ToF-SIMS is an ionization technique which produces strong fragmentation patterns that are poorly understood. No current database of oak wood compounds exists for ToF-SIMS. Hence, we provide ToF-SIMS spectra from reference compounds, caffeic acid, vanillin, eugenol, and cellulose, which are important during ageing of spirits in oak wood barrels.¹

The four compounds were purchased from Sigma Aldrich. The compounds in solid form were dissolved in ethanol at a concentration of 1 mg/mL. Host silicon wafers were used and each standard solution was then deposited onto separated silicon wafers using a pipette, and then let to dry at room temperature.

The spectra were obtained using an IONTOF TOF-SIMS IV equipped with a 25 keV bismuth metal ion gun (LMIG). The instrument was operated in high current bunched mode. The primary ion dose was kept below the static limit of 10¹² ions/cm². The raster size, raster resolution, primary ion current and number of scans are specified for each sample. Figures and tables presented contain the identified peaks. In the figures, the full molecule is referred to with “M”.

## SPECIMEN DESCRIPTION (ACCESSION # 02030)

**Specimen:** Caffeic acid

CAS Registry #: 331-39-5

**Specimen Characteristics:** homogeneous; powder; unknown crystallinity; unknown conductivity; organic compound; powder;

**Chemical Name:** (2E)-3-(3,4-Dihydroxyphenyl)prop-2-enoic acid

**Source:** Sigma Aldrich

**Composition:** C₉H₈O₄

**Form:** Powder

**Structure:** N/A

**History & Significance:** Purity > 98.0 %

**As Received Condition:** Powder

**Analyzed Region:** 200 × 200 µm²

**Ex Situ Preparation/Mounting:** Deposit of the solubilized compound in ethanol (99,5%) onto a silicon wafer mounted onto the backmount IONTOF sample holder.

**In Situ Preparation:** N/A

**Charge Control Conditions and Procedures:** A low-energy electron flood gun was used. Flood gun filament current of 2.4 A. Surface potential was corrected (sample dependent).

**Temp. During Analysis:** 300 K

**Pressure During Analysis:** Between 1 × 10⁻⁵ and 1 × 10⁻⁶ Pa

**Pre-analysis Beam Exposure:** N/A

## SPECIMEN DESCRIPTION (ACCESSION # 02031)

**Specimen:** Vanillin

CAS Registry #: 121-33-5

<footnote>a) Present address: Cultural and Social History of the Arts (HiCSA), University of Paris 1 Panthéon-Sorbonne, Paris, France</footnote>

<footnote>b) Present address: Maastricht MultiModal Molecular Imaging Institute (M4i), Maastricht University, Maastricht, The Netherlands</footnote>

<footnote>c) Electronic mail: alain.brunelle@cnrs.fr</footnote>
<figure><img src="image_3.png" /></figure>

**Specimen Characteristics:** homogeneous; powder; unknown crystallinity; unknown conductivity; organic compound; powder;

**Chemical Name:** 4-hydroxy-3-methoxybenzaldehyde

**Source:** Sigma Aldrich

**Composition:** C₈H₈O₃

**Form:** Powder

**Structure:** N/A

**History & Significance:** Purity 99 %

**As Received Condition:** Powder

**Analyzed Region:** 500 × 500 µm²

**Ex Situ Preparation/Mounting:** Deposit of the solubilized compound in ethanol (99,5%) onto a silicon wafer mounted onto the backmount IONTOF sample holder.

**In Situ Preparation:** N/A

**Charge Control Conditions and Procedures:** A low-energy electron flood gun was used. Flood gun filament current of 2.4 A. Surface potential was corrected (sample dependent).

**Temp. During Analysis:** 300 K

**Pressure During Analysis:** Between 1 × 10⁻⁵ and 1 × 10⁻⁶ Pa

**Pre-analysis Beam Exposure:** N/A

## SPECIMEN DESCRIPTION (ACCESSION # 02032)

**Specimen:** Eugenol

**CAS Registry #:** 97-53-0

**Specimen Characteristics:** homogeneous; powder; unknown crystallinity; unknown conductivity; organic compound; powder;

**Chemical Name:** 2-Methoxy-4-(prop-2-en-1-yl)phenol

**Source:** Sigma Aldrich

**Composition:** C₁₀H₁₂O₂

**Form:** Powder

**Structure:** N/A

**History & Significance:** Purity > 98 %

**As Received Condition:** Powder

**Analyzed Region:** 500 × 500 µm²

**Ex Situ Preparation/Mounting:** Deposit of the solubilized compound in ethanol (99,5%) onto a silicon wafer mounted onto the backmount IONTOF sample holder.

**In Situ Preparation:** N/A

**Charge Control Conditions and Procedures:** A low-energy electron flood gun was used. Flood gun filament current of 2.4 A. Surface potential was corrected (sample dependent).

**Temp. During Analysis:** 300 K

**Pressure During Analysis:** Between 1 × 10⁻⁵ and 1 × 10⁻⁶ Pa

**Pre-analysis Beam Exposure:** N/A

## SPECIMEN DESCRIPTION (ACCESSION # 02033)

**Specimen:** Cellulose

**CAS Registry #:** 9004-34-6

**Specimen Characteristics:** homogeneous; powder; unknown crystallinity; unknown conductivity; organic compound; powder;

**Chemical Name:** Cellulose

**Source:** Sigma Aldrich

**Composition:** (C₆H₁₀O₅)ₐ

**Form:** Powder

**Structure:** N/A

**History & Significance:** Purity > 95 %

**As Received Condition:** Powder

**Analyzed Region:** 500 × 500 µm²

**Ex Situ Preparation/Mounting:** Deposit of the solubilized compound in ethanol (99,5%) onto a silicon wafer mounted onto the backmount IONTOF sample holder.

**In Situ Preparation:** N/A

**Charge Control Conditions and Procedures:** A low-energy electron flood gun was used. Flood gun filament current of 2.4 A. Surface potential was corrected (sample dependent).

**Temp. During Analysis:** 300 K

**Pressure During Analysis:** Between 1 × 10⁻⁵ and 1 × 10⁻⁶ Pa

**Pre-analysis Beam Exposure:** N/A

## INSTRUMENT CONFIGURATION

**Manufacturer and Model:** IONTOF TOF-SIMS IV

**Analyzer Type:** time-of-flight

**Sample Rotation:** no

**Rotation Rate:** 0 rpm

**Oxygen Flood Source:** None

**Oxygen Flood Pressure:** N/A

**Other Flood Source:** None

**Other Flood Pressure:** N/A

**Unique Instrument Features Used:** None

**Energy Acceptance Window:** 20 eV

**Post-acceleration Voltage:** 10000 eV

**Sample Bias:** 10-20 eV

**Specimen Normal-to-analyzer (Θe):** 0°

### ■Ion Sources

#### Ion Source 1 of 1

**Purpose of this Ion Source:** analysis beam

**Ion Source Manufacturer:** IONTOF GmbH

**Ion Source Model:** LMIG with bismuth cluster (25 keV)

**Beam Mass Filter:** yes

**Beam Species and Charge State:** Bi₃⁺

**Beam Gating Used:** Double pulsed + bunched

**Additional Beam Comments:** None

**Beam Voltage:** 25000 eV
<figure><img src="image_4.png" /></figure>

**Net Beam Voltage (impact voltage):** 25000 eV

**Ion Pulse Width:** 0.8 – 1.2 ns

**Ion Pulse Rate:** 8.33 kHz

**DC Beam Current:** ~10 nA

**Pulsed Beam Current:** ~0.00041 nA

**Current Measurement Method:** Faraday cup

**Beam Diameter:** ~3 µm

**Beam Raster Size:** 500 × 500 µm²

**Raster Pixel Dimensions:** 128 x 128

**Beam Incident Angle:** 45°

**Source-to-Analyzer Angle:** 45°

## ACKNOWLEDGMENTS

This work was financially supported by the Agence Nationale de la Recherche (grant No. ANR-21-CE29-0026 MULTI-ANGEL-MSI) and by the DIM PAMIR (IDF-DIM-PAMIR-2023-4-001 ANGELSHARE).

## AUTHOR DECLARATIONS

### Conflicts of Interest (required)

The authors have no conflicts of interest to disclose.

### Author Contributions (if applicable)

**Aline Cournut:** Writing – original draft (lead). **Sarah Belhachmi:** Investigation (lead). **Caroline Bouvier:** Investigation, Writing – review and editing (lead). **Alain Brunelle:** Conceptualization (lead); Writing – review and editing (lead).

## DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available within the article and its supplementary material.

## REFERENCES

1. W. De Gruyter, *Volume 1 Wood Chemistry and Wood Biotechnology*, Berlin, New York:, 2009.
https://doi.org/10.1515/9783110213409
<figure><img src="image_5.png" /></figure>

<table><caption>SPECTRAL FEATURES TABLE</caption><thead><tr><th>Spectrum ID #</th><th>Mass (Δm), Da</th><th>Species</th><th>Peak Assignment</th></tr></thead><tbody><tr><td rowspan="3">02030-01</td><td>163.039 (3.4)</td><td>[M-H<sub>2</sub>O+H]<sup>+</sup></td><td>C<sub>9</sub>H<sub>7</sub>O<sub>3</sub><sup>+</sup></td></tr><tr><td>180.039 (-16.7)</td><td>[M]<sup>+</sup></td><td>C<sub>9</sub>H<sub>8</sub>O<sub>4</sub><sup>+</sup></td></tr><tr><td>181.052 (13.0)</td><td>[M+H]<sup>+</sup></td><td>C<sub>9</sub>H<sub>9</sub>O<sub>4</sub><sup>+</sup></td></tr></tbody></table>

<figure><img src="image_6.png" /></figure>

<table><tr><td>Accession #</td><td>02030-01</td></tr><tr><td>■ Specimen:</td><td>Caffeic Acid</td></tr><tr><td>■ Technique:</td><td>ToF-SIMS</td></tr><tr><td>Instrument:</td><td>IONTOF TOF-SIMS IV</td></tr><tr><td>Analyzer Type:</td><td>Time-of-flight</td></tr><tr><td>Analyzer Mass Resolving Power:</td><td>4572 m/Δm</td></tr><tr><td>Mass Resolving Power Determined at:</td><td>27.02 Da</td></tr><tr><td>Species Used for Mass Calibration:</td><td>CH<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>5</sub><sup>+</sup>, C<sub>3</sub>H<sub>5</sub><sup>+</sup>, and C<sub>4</sub>H<sub>5</sub><sup>+</sup></td></tr><tr><td>Specimen Normal-to-Analyzer:</td><td>0°</td></tr><tr><td>Source-to-Analyzer Angle:</td><td>45°</td></tr><tr><td>Primary Beam Ion Gun:</td><td>LMIG</td></tr><tr><td>Primary Ion Species:</td><td>Bi<sub>3</sub><sup>+</sup></td></tr><tr><td>Primary Ion Dose:</td><td>4.03 x 10<sup>11</sup> ion/cm<sup>2</sup></td></tr><tr><td>Primary Ion Pulse Width:</td><td>0.8 – 1.2 ns</td></tr><tr><td>Primary Ion Pulse Rate:</td><td>6.66 kHz</td></tr><tr><td>Net Beam Voltage:</td><td>25000 eV</td></tr></table>
<figure><img src="image_7.png" /></figure>

<table><tr><td>Pulsed Beam Current:</td><td>0.00045 nA</td></tr><tr><td>DC Beam Current:</td><td>10.0 nA</td></tr><tr><td>Beam Diameter:</td><td>~3 µm</td></tr><tr><td>Beam Raster Size:</td><td>200 x 200 µm²</td></tr><tr><td>Raster Pixel Dimensions:</td><td>128 x 128</td></tr><tr><td>Beam Incident Angle:</td><td>45°</td></tr><tr><td>Secondary Source Polarity:</td><td>positive</td></tr><tr><td>Mass Range Minimum:</td><td>0 Da</td></tr><tr><td>Mass Range Maximum:</td><td>2000 Da</td></tr><tr><td>Spectrum Dead Time Corrected</td><td>Yes</td></tr><tr><td>Total Spectral Acquisition Time:</td><td>197 s</td></tr><tr><td>Comment:</td><td>The mass spectrum was contaminated by polydimethylsiloxane (PDMS), with intense ion peaks at m/z 73.054 (SiC<sub>3</sub>H<sub>9</sub><sup>+</sup>), 147.076 (Si<sub>2</sub>C<sub>5</sub>H<sub>15</sub>O<sup>+</sup>), 207.042 (Si<sub>3</sub>C<sub>5</sub>H<sub>15</sub>O<sub>3</sub><sup>+</sup>) and 221.102 (Si<sub>3</sub>C<sub>7</sub>H<sub>21</sub>O<sub>2</sub><sup>+</sup>), labeled * when visible in the part of mass spectra shown.</td></tr></table>
<figure><img src="image_8.png" /></figure>

This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI: 10.1116/6.0004753

<figure><img src="image_9.png" /><figcaption>SPECTRAL FEATURES TABLE</figcaption></figure>

<table><thead><tr><th>Spectrum ID #</th><th>Mass (Δm), Da</th><th>Species</th><th>Peak Assignment</th></tr></thead><tbody><tr><td rowspan="3">02031-01</td><td>151.043 (25.5)</td><td>[M-H<sub>2</sub>+H]<sup>+</sup></td><td>C<sub>8</sub>H<sub>7</sub>O<sub>3</sub><sup>+</sup></td></tr><tr><td>152.054 (46.9))</td><td>[M]<sup>+</sup></td><td>C<sub>8</sub>H<sub>8</sub>O<sub>3</sub><sup>+</sup></td></tr><tr><td>197.026 (38.2)</td><td>[M-H+2Na]<sup>+</sup></td><td>C<sub>8</sub>H<sub>7</sub>O<sub>3</sub>Na<sup>+</sup></td></tr></tbody></table>

Accession # 02031-01

■ Specimen: Vanillin

■ Technique: ToF-SIMS

Instrument: IONTOF TOF-SIMS IV

Analyzer Type: Time-of-flight

Analyzer Mass Resolving Power: 2956 m/Δm

Mass Resolving Power Determined at: 27.02 Da

Species Used for Mass Calibration: CH<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>5</sub><sup>+</sup>, C<sub>3</sub>H<sub>3</sub><sup>+</sup>, and C<sub>3</sub>H<sub>5</sub><sup>+</sup>

Specimen Normal-to-Analyzer: 0°

Source-to-Analyzer Angle: 45°

Primary Beam Ion Gun: LMIG

Primary Ion Species: Bi<sub>3</sub><sup>+</sup>

Primary Ion Dose: 1.68 x 10<sup>11</sup> ion/cm<sup>2</sup>

Primary Ion Pulse Width: 0.8 – 1.2 ns

Primary Ion Pulse Rate: 8.33 kHz

Net Beam Voltage: 25000 eV
<figure><img src="image_10.png" /></figure>

This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI: 10.1116/6.0004753

<table><tr><td>Pulsed Beam Current:</td><td>0.00041 nA</td></tr><tr><td>DC Beam Current:</td><td>10 nA</td></tr><tr><td>Beam Diameter:</td><td>~3 µm</td></tr><tr><td>Beam Raster Size:</td><td>500 x 500 µm²</td></tr><tr><td>Raster Pixel Dimensions:</td><td>128 x 128</td></tr><tr><td>Beam Incident Angle:</td><td>45°</td></tr><tr><td>Secondary Source Polarity:</td><td>positive</td></tr><tr><td>Mass Range Minimum:</td><td>0 Da</td></tr><tr><td>Mass Range Maximum:</td><td>1250 Da</td></tr><tr><td>Spectrum Dead Time Corrected</td><td>Yes</td></tr><tr><td>Total Spectral Acquisition Time:</td><td>197 s</td></tr></table>
<figure><img src="image_11.png" /></figure>

<table><caption>SPECTRAL FEATURES TABLE</caption><thead><tr><th>Spectrum ID #</th><th>Mass (Δm), Da</th><th>Species</th><th>Peak Assignment</th></tr></thead><tbody><tr><td rowspan="5">02032-01</td><td>137.061 (11.3)</td><td>[M-2CH<sub>2</sub>+H]<sup>+</sup></td><td>C<sub>8</sub>H<sub>9</sub>O<sub>2</sub><sup>+</sup></td></tr><tr><td>161.062 (15.3)</td><td>[M-2H<sub>2</sub>+H]<sup>+</sup></td><td>C<sub>10</sub>H<sub>9</sub>O<sub>2</sub><sup>+</sup></td></tr><tr><td>162.063 (-27.0)</td><td>[M-H<sub>2</sub>]<sup>**</sup></td><td>C<sub>10</sub>H<sub>10</sub>O<sub>2</sub><sup>+</sup></td></tr><tr><td>163.082 (41.2)</td><td>[M-H<sub>2</sub>+H]<sup>+</sup></td><td>C<sub>10</sub>H<sub>11</sub>O<sub>2</sub><sup>+</sup></td></tr><tr><td>164.084 (6.0)</td><td>[M]<sup>**</sup></td><td>C<sub>10</sub>H<sub>12</sub>O<sub>2</sub><sup>+</sup></td></tr></tbody></table>

<figure><img src="image_12.png" /></figure>

<table><tr><td>Accession #</td><td>02032-01</td></tr><tr><td>■ Specimen:</td><td>Eugenol</td></tr><tr><td>■ Technique:</td><td>ToF-SIMS</td></tr><tr><td>Instrument:</td><td>IONTOF TOF-SIMS IV</td></tr><tr><td>Analyzer Type:</td><td>Time-of-flight</td></tr><tr><td>Analyzer Mass Resolving Power:</td><td>3779 m/Δm</td></tr><tr><td>Mass Resolving Power Determined at:</td><td>27.02 Da</td></tr><tr><td>Species Used for Mass Calibration:</td><td>CH<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>5</sub><sup>+</sup>, C<sub>3</sub>H<sub>3</sub><sup>+</sup>, C<sub>3</sub>H<sub>5</sub><sup>+</sup>, and C<sub>4</sub>H<sub>5</sub><sup>+</sup></td></tr><tr><td>Specimen Normal-to-Analyzer:</td><td>0°</td></tr><tr><td>Source-to-Analyzer Angle:</td><td>45°</td></tr><tr><td>Primary Beam Ion Gun:</td><td>LMIG</td></tr><tr><td>Primary Ion Species:</td><td>Bi<sub>3</sub><sup>+</sup></td></tr><tr><td>Primary Ion Dose:</td><td>1.64 x 10<sup>11</sup> ion/cm<sup>2</sup></td></tr><tr><td>Primary Ion Pulse Width:</td><td>0.8 – 1.2 ns</td></tr></table>
<figure><img src="image_13.png" /></figure>

<table><tr><td>Primary Ion Pulse Rate:</td><td>8.33 kHz</td></tr><tr><td>Net Beam Voltage:</td><td>25000 eV</td></tr><tr><td>Pulsed Beam Current:</td><td>0.00040 nA</td></tr><tr><td>DC Beam Current:</td><td>10.0 nA</td></tr><tr><td>Beam Diameter:</td><td>~3 µm</td></tr><tr><td>Beam Raster Size:</td><td>500 x 500 µm²</td></tr><tr><td>Raster Pixel Dimensions:</td><td>128 x 128</td></tr><tr><td>Beam Incident Angle:</td><td>45°</td></tr><tr><td>Secondary Source Polarity:</td><td>positive</td></tr><tr><td>Mass Range Minimum:</td><td>0 Da</td></tr><tr><td>Mass Range Maximum:</td><td>1250 Da</td></tr><tr><td>Spectrum Dead Time Corrected</td><td>Yes</td></tr><tr><td>Total Spectral Acquisition Time:</td><td>197 s</td></tr><tr><td>Comment:</td><td>The mass spectrum was contaminated by polydimethylsiloxane (PDMS), with intense ion peaks at m/z 73.054 (SiC<sub>3</sub>H<sub>9</sub><sup>+</sup>), 147.076 (Si<sub>2</sub>C<sub>5</sub>H<sub>15</sub>O<sup>+</sup>), 207.042 (Si<sub>3</sub>C<sub>5</sub>H<sub>15</sub>O<sub>3</sub><sup>+</sup>) and 221.102 (Si<sub>3</sub>C<sub>7</sub>H<sub>21</sub>O<sub>2</sub><sup>+</sup>), labeled * when visible in the part of mass spectra shown.</td></tr></table>
<figure><img src="image_14.png" /></figure>

<table><caption>SPECTRAL FEATURES TABLE</caption><thead><tr><th>Spectrum ID #</th><th>Mass (Δm), Da</th><th>Species</th><th>Peak Assignment</th></tr></thead><tbody><tr><td rowspan="3">02033-01</td><td>145.050 (5.6)</td><td>[M-H<sub>2</sub>O+H]<sup>+</sup></td><td>C<sub>6</sub>H<sub>9</sub>O<sub>4</sub><sup>+</sup></td></tr><tr><td>163.068 (48.1)</td><td>[M+H]<sup>+</sup></td><td>C<sub>6</sub>H<sub>11</sub>O<sub>5</sub><sup>+</sup></td></tr><tr><td>322.100 (34.1)</td><td>[2M-H<sub>2</sub>]<sup>+</sup></td><td>C<sub>12</sub>H<sub>18</sub>O<sub>10</sub><sup>+</sup></td></tr></tbody></table>

<figure><img src="image_15.png" /></figure>

<table><tr><td>Accession #</td><td>02033-01</td></tr><tr><td>■ Specimen:</td><td>Cellulose</td></tr><tr><td>■ Technique:</td><td>ToF-SIMS</td></tr><tr><td>Instrument:</td><td>IONTOF TOF-SIMS IV</td></tr><tr><td>Analyzer Type:</td><td>Time-of-flight</td></tr><tr><td>Analyzer Mass Resolving Power:</td><td>2305 m/Δm</td></tr><tr><td>Mass Resolving Power Determined at:</td><td>27.02 Da</td></tr><tr><td>Species Used for Mass Calibration:</td><td>CH<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>3</sub><sup>+</sup>, C<sub>2</sub>H<sub>5</sub><sup>+</sup>, CH<sub>3</sub>O<sup>+</sup>, and C<sub>3</sub>H<sub>5</sub><sup>+</sup></td></tr><tr><td>Specimen Normal-to-Analyzer:</td><td>0°</td></tr><tr><td>Source-to-Analyzer Angle:</td><td>45°</td></tr><tr><td>Primary Beam Ion Gun:</td><td>LMIG</td></tr><tr><td>Primary Ion Species:</td><td>Bi<sub>3</sub><sup>+</sup></td></tr><tr><td>Primary Ion Dose:</td><td>1.68 x 10<sup>11</sup> ion/cm<sup>2</sup></td></tr><tr><td>Primary Ion Pulse Width:</td><td>0.8 – 1.2 ns</td></tr><tr><td>Primary Ion Pulse Rate:</td><td>8.33 kHz</td></tr><tr><td>Net Beam Voltage:</td><td>25000 eV</td></tr></table>
<figure><img src="image_16.png" /></figure>

This is the author's peer reviewed, accepted manuscript. However, the online version of record will be different from this version once it has been copyedited and typeset.
PLEASE CITE THIS ARTICLE AS DOI: 10.1116/6.0004753

<table><tr><td>Pulsed Beam Current:</td><td>0.00041 nA</td></tr><tr><td>DC Beam Current:</td><td>10 nA</td></tr><tr><td>Beam Diameter:</td><td>~3 µm</td></tr><tr><td>Beam Raster Size:</td><td>500 x 500 µm²</td></tr><tr><td>Raster Pixel Dimensions:</td><td>128 x 128</td></tr><tr><td>Beam Incident Angle:</td><td>45°</td></tr><tr><td>Secondary Source Polarity:</td><td>positive</td></tr><tr><td>Mass Range Minimum:</td><td>0 Da</td></tr><tr><td>Mass Range Maximum:</td><td>1250 Da</td></tr><tr><td>Spectrum Dead Time Corrected</td><td>Yes</td></tr><tr><td>Total Spectral Acquisition Time:</td><td>197 s</td></tr><tr><td>Comment:</td><td>The surface deposition was not flat enough. To improve the mass resolution and the accuracy of the m/z values, an ROI was generated to select only the flattest parts of the surface.</td></tr></table>