Abstract

Optical extinction by homogeneous, pure water droplets of 30 to 70μm diameter produced by a vibrating orifice aerosol generator has been studied by pulsed cavity ringdown (CRD) spectroscopy at λ=560  nm under ambient conditions. Experimental sensitivity of better than 1% achieved in measurements of CRD times enabled detection of changes in laser light losses per pass due to changes in the number and size of particles within the laser beam volume. By systematically changing the droplet size in the cavity while recording the CRD time, a periodic modulation in the value of the loss per pass was observed. The modulation is caused by the oscillatory nature of the extinction efficiency, which was subsequently inferred and compared with the results of theoretical calculations based on Mie theory.

© 2007 Optical Society of America

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    [CrossRef] [PubMed]
  28. R. M. Sayer, R. D. B. Gatherer, R. J. J. Gilham, and J. P. Reid, "Determination and validation of water droplet size distributions probed by cavity enhanced Raman scattering," Phys. Chem. Chem. Phys. 5, 3732-3739 (2003).
    [CrossRef]
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2007

T. J. A. Butler, J. L. Miller, and A. J. Orr-Ewing, "Cavity ring-down spectroscopy measurements of single aerosol particle extinction. I. The effect of position of a particle within the laser beam on extinction," J. Chem. Phys. 126, 174302 (2007).
[CrossRef] [PubMed]

J. L. Miller and A. J. Orr-Ewing, "Cavity ring-down spectroscopy measurements of single aerosol particle extinction. II. Extinction of light by an aerosol particle in an optical cavity excited by a cw laser," J. Chem. Phys. 126, 174303 (2007).
[CrossRef] [PubMed]

2006

R. J. Hopkins and J. P. Reid, "A comparative study of the mass and heat transfer dynamics of evaporating ethanol/water, methanol/water, and 1-propanol/water aerosol droplets," J. Phys. Chem. B 110, 3239-3249 (2006).
[CrossRef] [PubMed]

D. A. Lack, E. R. Lovejoy, T. Baynard, A. Pettersson, and A. R. Ravishankara, "Aerosol absorption measurements using photoacoustic spectroscopy: sensitivity, calibration, and uncertainty developments," Aerosol Sci. Technol. 40, 697-708 (2006).
[CrossRef]

A. W. Strawa, R. Elleman, A. G. Hallar, D. Covert, K. Ricci, R. Provencal, T. W. Owano, H. H. Jonsson, B. Schmid, A. P. Luu, K. Bokarius, and E. Andrews, "Comparison of in situ aerosol extinction and scattering coefficient measurements made during the aerosol intensive operating period," J. Geophys. Res. 111, D05S03, doi: (2006).
[CrossRef]

V. Bulatov, Y. Chen, A. Khalmanov, and I. Schechter, "Absorption and scattering characterization of airborne microparticulates by a cavity ringdown technique," Anal. Bioanal. Chem. 384, 155-160 (2006).
[CrossRef]

2005

B. A. Richman, A. A. Kachanov, B. A. Paldus, and A. A. Strawa, "Novel detection of aerosols: combined cavity ring-down and fluorescence spectroscopy," Opt. Express 13, 3376-3387 (2005).
[CrossRef] [PubMed]

H. Moosmüller, R. Varma, and W. P. Arnott, "Cavity ring-down and cavity-enhanced detection techniques for the measurement of aerosol extinction," Aerosol Sci. Technol. 39, 30-39 (2005).
[CrossRef]

2004

A. Pettersson, E. R. Lovejoy, C. A. Brock, S. S. Brown, and A. R. Ravishankara, "Measurement of aerosol optical extinction at 532 nm with pulsed cavity ring down spectroscopy," J. Aerosol Sci. 35, 995-1011 (2004).
[CrossRef]

2003

J. E. Thompson, H. D. Nasajpour, B. W. Smith, and J. D. Winefordner, "Atmospheric aerosol measurements by cavity ringdown turbidimetry," Aerosol Sci. Technol. 37, 221-230 (2003).
[CrossRef]

A. W. Strawa, R. Castaneda, T. Owano, D. S. Baer, and B. A. Paldus, "The measurement of aerosol optical properties using continuous wave cavity ring-down techniques," J. Atm. Ocean. Technol. 20, 454-465 (2003).
[CrossRef]

R. M. Sayer, R. D. B. Gatherer, R. J. J. Gilham, and J. P. Reid, "Determination and validation of water droplet size distributions probed by cavity enhanced Raman scattering," Phys. Chem. Chem. Phys. 5, 3732-3739 (2003).
[CrossRef]

2002

V. Bulatov, M. Fisher, and I. Schechter, "Aerosol analysis by cavity-ring-down laser spectroscopy," Anal. Chim. Acta 466, 1-9 (2002).
[CrossRef]

J. E. Thompson, B. W. Smith, and J. D. Winefordner, "Monitoring atmospheric particulate matter through cavity ring-down spectroscopy," Anal. Chem. 74, 1962-1967 (2002).
[CrossRef] [PubMed]

2001

J. D. Smith and D. B. Atkinson, "A portable pulsed cavity ring-down transmissometer for measurement of the optical extinction of the atmospheric aerosol," Analyst 126, 1216-1220 (2001).
[CrossRef] [PubMed]

H. Naus, W. Ubachs, P. F. Levelt, O. L. Polyansky, N. F. Zobov, and J. Tennyson, "Cavity-ring-down spectroscopy on water vapor in the range 555-604 nm," J. Mol. Spectrosc. 205, 117-121 (2001).
[CrossRef] [PubMed]

2000

G. Berden, R. Peeters, and G. Meijer, "Cavity ring-down spectroscopy: experimental schemes and applications," Int. Rev. Phys. Chem. 19, 565-607 (2000).
[CrossRef]

G. Durry and G. Megie, "In situ measurements of H2O from a stratospheric balloon by diode laser direct-differential absorption spectroscopy at 1.39 μm," Appl. Opt. 39, 5601-5608 (2000).
[CrossRef]

W. Widada, H. Kuze, Y. Xue, K. Maeda, and N. Takeuchi, "Long-path monitoring of atmospheric aerosol extinction with an automated laser positioning system," Rev. Sci. Instrum. 71, 546-550 (2000).
[CrossRef]

1999

1998

1978

1964

J. M. Schneider and C. D. Hendricks, "Source of uniform-sized liquid droplets," Rev. Sci. Instrum. 35, 1349-1350 (1964).
[CrossRef]

1878

Lord Rayleigh, "On the instability of jets," Proc. London Math. Soc. s1-10, 4-12 (1878).
[CrossRef]

Aerosol Sci. Technol.

D. A. Lack, E. R. Lovejoy, T. Baynard, A. Pettersson, and A. R. Ravishankara, "Aerosol absorption measurements using photoacoustic spectroscopy: sensitivity, calibration, and uncertainty developments," Aerosol Sci. Technol. 40, 697-708 (2006).
[CrossRef]

J. E. Thompson, H. D. Nasajpour, B. W. Smith, and J. D. Winefordner, "Atmospheric aerosol measurements by cavity ringdown turbidimetry," Aerosol Sci. Technol. 37, 221-230 (2003).
[CrossRef]

H. Moosmüller, R. Varma, and W. P. Arnott, "Cavity ring-down and cavity-enhanced detection techniques for the measurement of aerosol extinction," Aerosol Sci. Technol. 39, 30-39 (2005).
[CrossRef]

Anal. Bioanal. Chem.

V. Bulatov, Y. Chen, A. Khalmanov, and I. Schechter, "Absorption and scattering characterization of airborne microparticulates by a cavity ringdown technique," Anal. Bioanal. Chem. 384, 155-160 (2006).
[CrossRef]

Anal. Chem.

J. E. Thompson, B. W. Smith, and J. D. Winefordner, "Monitoring atmospheric particulate matter through cavity ring-down spectroscopy," Anal. Chem. 74, 1962-1967 (2002).
[CrossRef] [PubMed]

Anal. Chim. Acta

V. Bulatov, M. Fisher, and I. Schechter, "Aerosol analysis by cavity-ring-down laser spectroscopy," Anal. Chim. Acta 466, 1-9 (2002).
[CrossRef]

Analyst

J. D. Smith and D. B. Atkinson, "A portable pulsed cavity ring-down transmissometer for measurement of the optical extinction of the atmospheric aerosol," Analyst 126, 1216-1220 (2001).
[CrossRef] [PubMed]

Appl. Opt.

Int. Rev. Phys. Chem.

G. Berden, R. Peeters, and G. Meijer, "Cavity ring-down spectroscopy: experimental schemes and applications," Int. Rev. Phys. Chem. 19, 565-607 (2000).
[CrossRef]

J. Aerosol Sci.

A. Pettersson, E. R. Lovejoy, C. A. Brock, S. S. Brown, and A. R. Ravishankara, "Measurement of aerosol optical extinction at 532 nm with pulsed cavity ring down spectroscopy," J. Aerosol Sci. 35, 995-1011 (2004).
[CrossRef]

J. Atm. Ocean. Technol.

A. W. Strawa, R. Castaneda, T. Owano, D. S. Baer, and B. A. Paldus, "The measurement of aerosol optical properties using continuous wave cavity ring-down techniques," J. Atm. Ocean. Technol. 20, 454-465 (2003).
[CrossRef]

J. Chem. Phys.

T. J. A. Butler, J. L. Miller, and A. J. Orr-Ewing, "Cavity ring-down spectroscopy measurements of single aerosol particle extinction. I. The effect of position of a particle within the laser beam on extinction," J. Chem. Phys. 126, 174302 (2007).
[CrossRef] [PubMed]

J. L. Miller and A. J. Orr-Ewing, "Cavity ring-down spectroscopy measurements of single aerosol particle extinction. II. Extinction of light by an aerosol particle in an optical cavity excited by a cw laser," J. Chem. Phys. 126, 174303 (2007).
[CrossRef] [PubMed]

J. Geophys. Res.

A. W. Strawa, R. Elleman, A. G. Hallar, D. Covert, K. Ricci, R. Provencal, T. W. Owano, H. H. Jonsson, B. Schmid, A. P. Luu, K. Bokarius, and E. Andrews, "Comparison of in situ aerosol extinction and scattering coefficient measurements made during the aerosol intensive operating period," J. Geophys. Res. 111, D05S03, doi: (2006).
[CrossRef]

J. Mol. Spectrosc.

H. Naus, W. Ubachs, P. F. Levelt, O. L. Polyansky, N. F. Zobov, and J. Tennyson, "Cavity-ring-down spectroscopy on water vapor in the range 555-604 nm," J. Mol. Spectrosc. 205, 117-121 (2001).
[CrossRef] [PubMed]

J. Phys. Chem. B

R. J. Hopkins and J. P. Reid, "A comparative study of the mass and heat transfer dynamics of evaporating ethanol/water, methanol/water, and 1-propanol/water aerosol droplets," J. Phys. Chem. B 110, 3239-3249 (2006).
[CrossRef] [PubMed]

Opt. Express

Opt. Lett.

Phys. Chem. Chem. Phys.

R. M. Sayer, R. D. B. Gatherer, R. J. J. Gilham, and J. P. Reid, "Determination and validation of water droplet size distributions probed by cavity enhanced Raman scattering," Phys. Chem. Chem. Phys. 5, 3732-3739 (2003).
[CrossRef]

Proc. London Math. Soc.

Lord Rayleigh, "On the instability of jets," Proc. London Math. Soc. s1-10, 4-12 (1878).
[CrossRef]

Rev. Sci. Instrum.

J. M. Schneider and C. D. Hendricks, "Source of uniform-sized liquid droplets," Rev. Sci. Instrum. 35, 1349-1350 (1964).
[CrossRef]

W. Widada, H. Kuze, Y. Xue, K. Maeda, and N. Takeuchi, "Long-path monitoring of atmospheric aerosol extinction with an automated laser positioning system," Rev. Sci. Instrum. 71, 546-550 (2000).
[CrossRef]

Other

J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. van der Linden, X. Dai, K. Maskell, and C. A. Johnson, eds., Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2001).
[PubMed]

C. F. Bohren and D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, 1998).
[CrossRef]

"Model 3450 Vibrating Orifice Aerosol Generator-Instruction Manual" (TSI Incorporated, Shoreview, MN, USA).

J. H. Seinfeld and S. N. Pandis, Atmospheric Chemistry and Physics: From Air Pollution to Climate Change (Wiley, 1998).

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Figures (9)

Fig. 1
Fig. 1

Extinction efficiency of water droplets as a function of size parameter, α. The corresponding droplet diameter, d, for 560   nm illumination is shown on the upper x axis. The regions α ( 0 , 25 ) and α ( 290 , 340 ) are shown enlarged (see insets).

Fig. 2
Fig. 2

Experimental setup for investigation of micrometer size water droplets as generated by the VOAG and probed with cavity ringdown spectroscopy. A schematic illustration of the overlap geometry between the laser beam and droplet train is shown in the upper right corner. HW, half-waveplate; OI, optical isolator; PD, photodiode; I, iris; F, filter; HRM, high reflectivity mirror.

Fig. 3
Fig. 3

Variation in CRD time observed when two different frequencies ( f 1 = 103.5   kHz and f 2 = 54.5   kHz ) are applied at periodic time intervals to a piezoelectric crystal in contact with a 35 μ m orifice.

Fig. 4
Fig. 4

Loss per pass as a function of PZC modulation frequency due to water droplets produced using a 15 μ m orifice. A scaled f 1 / 3 curve is overlapped with the experimental data.

Fig. 5
Fig. 5

(a) CRD time due to the train of water droplets generated by the VOAG using a 20 μ m diameter orifice, plotted as a function of the modulation frequency applied to the piezoelectric crystal, which was swept between 110 and 60   kHz . A scaled f 1 / 3 curve is overlapped with the experimental data. (b) CRD time normalized with respect to change in the geometrical cross section and number of droplets.

Fig. 6
Fig. 6

Normalized loss per pass (i, black curve) and calculated extinction efficiency (ii, gray curve) as a function of size parameter for micrometer size homogeneous, spherical pure water droplets generated using (a) a 20 μ m and (b) a 30 μ m diameter orifice.

Fig. 7
Fig. 7

(a) Laser light losses per pass as a function of the position of the train of water droplets within the laser beam cross section. Measurements were done using a 20 μ m orifice and f = 65   kHz as the modulation frequency. (b) Normalized Gaussian beam intensity profile and the difference between the maximum and minimum intensity incident on a droplet of a certain size (30, 40, 50, 60, and 70 μ m ) as a function of its position within laser beam.

Fig. 8
Fig. 8

(a) Intensity of the scattered laser light as a function of angle θ, as measured from the forward direction, for pure water droplets characterized by the size parameter α = 270.272 . (b) Fraction of the laser light intensity scattered within angle θ < θ a as measured from the forward direction, for pure water droplets as a function of size parameter α ( θ a = 0.1 , 0.2, 0.3, 0.4, 0.5 degrees with increasing fraction at any size parameter, respectively).

Fig. 9
Fig. 9

Loss per pass as a function of size parameter α for water droplets probed with 560   nm laser light. Theoretical results were obtained by using the following values: 2 w t o t = 1.2   mm , f = ( 110 6 0 )   kHz , v = 10   m   s 1 , θ a = 0.4 degrees, and under the assumption of Gaussian laser beam intensity, (a) without and (b) with inclusion of forward scattering effect; (c) uniform laser beam intensity and with inclusion of forward scattering effect. (d) Loss per pass calculated as in (c), while θ a is varied from 0.4, 0.3, to 0.2 degrees from top to penultimate curve, and with laser beam diameters ( 2 w tot ) of 1.2, 2.2, and 3.8   mm , respectively.

Equations (10)

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α = 2 π r λ .
A exp = L c ( 1 τ 1 τ 0 ) ,
σ N p = σ geom Q ext ( α ) N p .
A theo = σ g e o m Q e x t ( α ) N p w t o t 2 π [ 1 F ( α ) ] .
d = ( 6 J f l o w π f ) 1 / 3 ,
N p = 2 w tot f v .
A t h e o = i = 1 N p σ I ( r i ) I t o t [ 1 F ( α ) ] ,
I ( r ) = I 0 e 2 r 2 w 2 ,
I t o t = π w 2 2 I 0 .
A t h e o = 2 σ g e o m Q e x t ( α ) π w 2 { 1 + 2 i = 1 N exp [ 2 w 2 ( i w t o t N ) 2 ] } × [ 1 F ( α ) ] ,

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