Real-time compositional analysis of submicrometre particles

Reents, W. D.; Downey, S. W.; Emerson, A. B.; Mujsce, A. M.; Muller, A. J.; Siconolfi, D. J.; Sinclair, J. D.; Swanson, Alistair G.

doi:10.1088/0963-0252/3/3/020

Cited by 10 publications

(14 citation statements)

References 8 publications

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“…The increase in ion signal thus does not scale linearly with the difference in mass of the two particles sizes and of the total material that is potentially ablated. Similar effects were observed for RbNO 3 and (NH 4 ) 2 SO 4 particles (Reents et al, 1994). This demonstrates the quantitative limitations of both ns-and fs-laser ablation.…”

Section: Ion Signal Intensity Variation With Particle Sizesupporting

confidence: 76%

Exploring femtosecond laser ablation in single-particle aerosol mass spectrometry

et al. 2018

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Abstract. Size, composition, and mixing state of individual aerosol particles can be analysed in real time using singleparticle mass spectrometry (SPMS). In SPMS, laser ablation is the most widely used method for desorption and ionization of particle components, often realizing both in one single step. Excimer lasers are well suited for this task due to their relatively high power density (10 7 -10 10 W cm −2 ) in nanosecond (ns) pulses at ultraviolet (UV) wavelengths and short triggering times. However, varying particle optical properties and matrix effects make a quantitative interpretation of this analytical approach challenging. In atmospheric SPMS applications, this influences both the mass fraction of an individual particle that is ablated, as well as the resulting mass spectral fragmentation pattern of the ablated material. The present study explores the use of shorter (femtosecond, fs) laser pulses for atmospheric SPMS. Its objective is to assess whether the higher laser power density of the fs laser leads to a more complete ionization of the entire particle and higher ion signal and thus improvement in the quantitative abilities of SPMS. We systematically investigate the influence of power density and pulse duration on airborne particle (polystyrene latex, SiO 2 , NH 4 NO 3 , NaCl, and custom-made core-shell particles) ablation and reproducibility of mass spectral signatures. We used a laser ablation aerosol time-of-flight single-particle mass spectrometer (LAAPTOF, AeroMegt GmbH), originally equipped with an excimer laser (wavelength 193 nm, pulse width 8 ns, pulse energy 4 mJ), and coupled it to an fs laser (Spectra Physics Solstice-100F ultrafast laser) with similar pulse energy but longer wavelengths (266 nm with 100 fs and 0.2 mJ, 800 nm with 100 fs and 3.2 mJ). We successfully coupled the freefiring fs laser with the single-particle mass spectrometer employing the fs laser light scattered by the particle to trigger mass spectra acquisition. Generally, mass spectra exhibit an increase in ion intensities (factor 1 to 5) with increasing laser power density (∼ 10 9 to ∼ 10 13 W cm −2 ) from ns to fs laser. At the same time, fs-laser ablation produces spectra with larger ion fragments and ion clusters as well as clusters with oxygen, which does not render spectra interpretation more simple compared to ns-laser ablation. The idea that the higher power density of the fs laser leads to a more complete particle ablation and ionization could not be substantiated in this study. Quantification of ablated material remains difficult due to incomplete ionization of the particle. Furthermore, the fslaser application still suffers from limitations in triggering it in a useful time frame. Further studies are needed to test potential advantages of fs-over ns-laser ablation in SPMS.

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Section: Ion Signal Intensity Variation With Particle Sizesupporting

confidence: 76%

Exploring femtosecond laser ablation in single-particle aerosol mass spectrometry

et al. 2018

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“…Similar effects were also observed by Reents (1994) for RbNO3 and (NH4)2SO4 particles. This demonstrates the 350 quantitative limitations of both ns-and fs-laser ablation.…”

supporting

confidence: 83%

Exploring femtosecond laser ablation in single particle aerosol mass spectrometry

Ramisetty¹,

Abdelmonem²,

Shen³

et al. 2017

Preprint

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Keywords: nanosecond laser ablation, femtosecond laser ablation, single particle mass spectrometry, atmospheric aerosols, aerosol mass spectrometry 10 AbstractSize, composition, and mixing state of individual aerosol particles can be analysed in real time using single particle mass spectrometry (SPMS). In SPMS, laser ablation is the most widely used method for desorption and ionization of particle components, often realizing both in one single step. Excimer lasers are well suited for this task due to their relatively high power density (10 7 W cm -2 -10 10 W cm -2 ) in nanosecond (ns) pulses at ultraviolet (UV) 15wavelengths, and short triggering times. However, varying particle optical properties and matrix effects make a quantitative interpretation of this analytical approach challenging. In atmospheric SPMS applications, this influences both the mass fraction of an individual particle that gets ablated, as well as the resulting mass spectral fragmentation pattern of the ablated material. The present study explores the use of shorter (femtosecond, fs) laser pulses for atmospheric SPMS, and systematically investigates the influence of power density and pulse duration 20 on airborne particle (polystyrene latex, SiO2, NH4NO3, NaCl, and custom-made core-shell particles) ablation and reproducibility of mass spectral signatures. We used a laser ablation aerosol time-of-flight single particle mass spectrometer (LAAPTOF, AeroMegt GmbH), originally equipped with an excimer laser (wavelength 193 nm, pulse width 8 ns, pulse energy 4 mJ), and coupled it to an fs-laser (Spectra Physics Solstice-100F ultrafast laser) with similar pulse energy, but longer wavelengths (266 nm with 100 fs and 0.2 mJ, 800 nm with 100 fs and 4 mJ, 25 respectively). Generally, mass spectra exhibit an increase in ion intensities (factor 1 to 5) with increasing laser power density (~10 8 W cm -2 to ~10 13 W cm -2) from ns-to fs-laser. At the same time, fs-laser ablation produces spectra with larger ion fragments and ion clusters, as well as clusters with oxygen, which does not render spectra interpretation more simple compared to ns-laser ablation. Quantification of ablated material remains difficult due to incomplete ionization of the particle. Furthermore, the fs-laser application still suffers from limitations in 30 triggering it in a useful timeframe. Further tests are needed to test potential advantages of fs-over ns-laser ablation in SPMS.

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“…Aerosols are introduced through a capillary nozzle and two skimmers into the source region of a linear TOFMS where a pulsed excimer laser is fired between 10 and 30 Hz. 141 With this design, particles between approximately 0.02-10 µm can be analyzed allowing for much smaller particle size analysis than with light scattering techniques. The excimer laser is focused to a rectangular spot size of 0.08 cm × 0.3 cm, operated at 308 nm with a 40 ns pulse width, allowing for a power density of approximately 1.7 × 10 8 W cm -2 .…”

Section: Reents (1994)mentioning

confidence: 99%