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Cheng W, Zhu H, Zheng F, Chu B, Wang R, Tao J, Zhang W, Tao P, Song C, Shang W, Fu B, Deng T. Phototaxis Flight of Microdroplets in a Laser. PHYSICAL REVIEW LETTERS 2024; 132:104001. [PMID: 38518322 DOI: 10.1103/physrevlett.132.104001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/27/2023] [Accepted: 01/24/2024] [Indexed: 03/24/2024]
Abstract
Phototaxis phenomenon is fundamental and critical for optical manipulation of micro-objects. Here, we report the size-dependent negative or positive phototaxis behaviors for microdroplets containing interfacial energy absorber flying in a laser. The critical diameters for such negative-to-positive turnover are studied through both experiments and simulation with different liquids and absorbers, which establishes the mechanism and reveals the role of both the liquid and the absorber inside the microdroplets. This study offers new insight for the manipulation of the phototaxis behavior of micro-objects, showing potential applications in optical trapping and transporting systems that involve light-microdroplet interactions.
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Affiliation(s)
- Weizheng Cheng
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Hanrui Zhu
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Feiyu Zheng
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Ben Chu
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Ruitong Wang
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Jinran Tao
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Wanli Zhang
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Peng Tao
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Chengyi Song
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Wen Shang
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Benwei Fu
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Tao Deng
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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Lawrence A, Akers BF. Propagation of high energy lasers through clouds: modeling and simulation. APPLIED OPTICS 2020; 59:10207-10216. [PMID: 33361948 DOI: 10.1364/ao.404526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 10/12/2020] [Indexed: 06/12/2023]
Abstract
A model for 10.6 µm high energy laser beam interaction with a uniform, monodisperse cloud of water droplets is developed. The model includes droplet and vapor heating as well as droplet shattering in the "fast regime" as defined in Appl. Opt.28, 3671 (1989)APOPAI0003-693510.1364/AO.28.003671. The cloud dynamics feed back on the laser via changes in the complex refractive index. In one space dimension, the model is solved exactly, including an explicit formula for the front of the cleared channel. Numerical simulations are conducted for the axisymmetric three-dimensional case. Model predictions and limitations are discussed.
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Wolf JP. Short-pulse lasers for weather control. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:026001. [PMID: 28783040 DOI: 10.1088/1361-6633/aa8488] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1-1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015-1017 cm-3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013-1014 W cm-2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.
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Affiliation(s)
- J P Wolf
- Department of Applied Physics (GAP), University of Geneva, 1211 Geneva 4, Switzerland
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Klein AL, Lohse D, Versluis M, Gelderblom H. Apparatus to control and visualize the impact of a high-energy laser pulse on a liquid target. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:095102. [PMID: 28964175 DOI: 10.1063/1.4989634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We present an experimental apparatus to control and visualize the response of a liquid target to a laser-induced vaporization. We use a millimeter-sized drop as target and present two liquid-dye solutions that allow a variation of the absorption coefficient of the laser light in the drop by seven orders of magnitude. The excitation source is a Q-switched Nd:YAG laser at its frequency-doubled wavelength emitting nanosecond pulses with energy densities above the local vaporization threshold. The absorption of the laser energy leads to a large-scale liquid motion at time scales that are separated by several orders of magnitude, which we spatiotemporally resolve by a combination of ultra-high-speed and stroboscopic high-resolution imaging in two orthogonal views. Surprisingly, the large-scale liquid motion upon laser impact is completely controlled by the spatial energy distribution obtained by a precise beam-shaping technique. The apparatus demonstrates the potential for accurate and quantitative studies of laser-matter interactions.
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Affiliation(s)
- Alexander L Klein
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, JM Burgers Center, and MESA+ Center for Nanotechnology, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Detlef Lohse
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, JM Burgers Center, and MESA+ Center for Nanotechnology, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Michel Versluis
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, JM Burgers Center, and MESA+ Center for Nanotechnology, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Hanneke Gelderblom
- Physics of Fluids Group, Max Planck Center Twente for Complex Fluid Dynamics, JM Burgers Center, and MESA+ Center for Nanotechnology, Department of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Sun H, Liu Y, Ju J, Tian Y, Bai Y, Liu Y, Du S, Wang C, Wang T, Liu J, Chin SL, Li R, Xu Z. Picosecond laser-induced water condensation in a cloud chamber. OPTICS EXPRESS 2016; 24:20494-20506. [PMID: 27607654 DOI: 10.1364/oe.24.020494] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigated water condensation in a laboratory cloud chamber induced by picosecond (ps) laser pulses at ~350 ps (800 nm/1-1000 Hz) with a maximum peak power of ~25 MW. The peak power was much lower than the critical power for self-focusing in air (~3-10 GW depending on the pulse duration). Sparks, airflow and snow formation were observed under different laser energies or repetition rates. It was found that weaker ps laser pulses can also induce water condensation by exploding and breaking down ice crystals and/or water droplets into tiny particles although there was no formation of laser filament. These tiny particles would grow until precipitation in a super-saturation zone due to laser-induced airflow in a cold region with a large temperature gradient.
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2H,3H-decafluoropentane-based nanodroplets: new perspectives for oxygen delivery to hypoxic cutaneous tissues. PLoS One 2015; 10:e0119769. [PMID: 25781463 PMCID: PMC4362938 DOI: 10.1371/journal.pone.0119769] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 01/16/2015] [Indexed: 01/20/2023] Open
Abstract
Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues.
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Sugiyama A, Nakajima A. Wavelength Dependence of IR Laser for Dual-laser Shattering of a Water Microdroplet. CHEM LETT 2012. [DOI: 10.1246/cl.2012.1481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Akinori Sugiyama
- Department of Chemistry, Faculty of Science and Technology, Keio University
| | - Atsushi Nakajima
- Department of Chemistry, Faculty of Science and Technology, Keio University
- JST-ERATO, Nakajima Designer Nanocluster Assembly Project
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Murphy DM. The design of single particle laser mass spectrometers. MASS SPECTROMETRY REVIEWS 2007; 26:150-65. [PMID: 17043988 DOI: 10.1002/mas.20113] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
This review explores some of the design choices made with single particle mass spectrometers. Different instruments have used various configurations of inlets, particle sizing techniques, ionization lasers, mass spectrometers, and other components. Systematic bias against non-spherical particles probably exceeds a factor of 2 for all instruments. An ionization laser tradeoff is the relatively poor beam quality and reliability of an excimer laser versus the longer wavelengths and slower response time of an Nd-YAG laser. Single particle instruments can make special demands on the speed and dynamic range of the mass spectrometers. This review explains some of the choices made for instruments that were developed for different types of measurements in the atmosphere. Some practical design notes are also given from the author's experience with each section of the instrument.
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Affiliation(s)
- Daniel M Murphy
- Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado 80305, USA.
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Woods, Miller RE, Baer T. The Internal Energy of Neutral Ethylene Glycol Molecules Created in the Laser Vaporization of Aerosol Particles. J Phys Chem A 2003. [DOI: 10.1021/jp0218387] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Woods
- Department of Chemistry,University of North Carolina, Chapel Hill, North Carolina 27599-3290
| | - Roger E. Miller
- Department of Chemistry,University of North Carolina, Chapel Hill, North Carolina 27599-3290
| | - Tomas Baer
- Department of Chemistry,University of North Carolina, Chapel Hill, North Carolina 27599-3290
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DeForest CL, Qian J, Miller RE. Time-resolved studies of the interactions between pulsed lasers and aerosols. APPLIED OPTICS 2002; 41:5804-5813. [PMID: 12269580 DOI: 10.1364/ao.41.005804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Studies of the interaction between a pulsed CO2 laser and micrometer-sized aqueous and organic particles by use of light-scattering methods and step-scan Fourier-transform infrared (FTIR) spectroscopy are reported. Visible two-color extinction experiments indicate primary particle shattering, accompanied by a high fraction of vaporization, followed by secondary particle evaporation. The extent of the latter depends on the pulse intensity and particle composition. Angle-resolved light-scattering investigations provide insight into the aerosol size distribution and temperature following the pulsed heating event. The time dependence of the vapor plume, monitored with step-scan FTIR spectroscopy, confirms that a large fraction of the initial particle is quickly evaporated during the shattering event, followed by secondary fragment evaporation and thermal expansion.
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Affiliation(s)
- Cindy L DeForest
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290, USA
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Woods E, Smith GD, Miller RE, Baer T. Depth profiling of heterogeneously mixed aerosol particles using single-particle mass spectrometry. Anal Chem 2002; 74:1642-9. [PMID: 12043599 DOI: 10.1021/ac0110909] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Infrared laser evaporation of single aerosol particles in a vacuum followed by vacuum ultraviolet (VUV) laser ionization and time-of-flight mass spectroscopy of the resulting vapor provides a depth profile of the particle's composition. Analyzing glycerol particles coated with 60-150-nm coatings of oleic acid using either a CO2 laser or a tunable optical parametric oscillator as an evaporation laser results in mass spectra that depend on the IR laser power. Low infrared laser powers incompletely vaporize particles and preferentially probe the composition of the surface layers of the particle, but high laser powers evaporate the entire particle and produce spectra representative of the particle's total composition. In the limit of low laser power, the fraction of oleic acid in the mass spectra is as much as 50 times greater than the fraction of oleic acid in the particle, providing a surface-layer-specific characterization. The OPO laser provides even more surface specificity, producing an [oleic acid]/[glycerol] ratio as much as four times larger (for a 60-nm coating) than that obtained using the CO2 laser. The infrared laser power required to sample the core of the particle increases with the thickness of the coating and is sensitive to changes in the coating thickness on the order of 10 nm. In contrast to these intuitively appealing results, high CO2 laser powers (approximately 90 mJ/pulse) produce mass spectra that, at short delays between the CO2 and VUV lasers, show enrichment of the core material rather than the coating. Likewise, tuning the OPO to frequencies that are resonant with the core material but transparent to the coating also results in selective detection of the core. The results suggest that a shattering mechanism dominates the vaporization dynamics in these situations.
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Affiliation(s)
- Ephraim Woods
- Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290, USA
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Owens MA, Davis CC, Dickerson RR. A Photothermal Interferometer for Gas-Phase Ammonia Detection. Anal Chem 1999; 71:1391-9. [DOI: 10.1021/ac980810h] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Melody Avery Owens
- Chemical Physics Program, University of Maryland, College Park, Maryland 20742
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Zemlyanov AA, Geints YE, Kabanov AM, Armstrong RL. Investigation of laser-induced destruction of droplets by acoustic methods. APPLIED OPTICS 1996; 35:6062-6068. [PMID: 21127621 DOI: 10.1364/ao.35.006062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Experimental investigations of acoustic signals generated by individual laser-irradiated water droplets are reported. The dependence of droplet destruction thresholds on droplet radius and radiative heating rate is determined. A theoretical explanation of our experimental results is provided in terms of a model that includes the processes of droplet evaporation and fragmentation in response to intense laser heating.
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Geints YE, Zemlyanov AA, Armstrong RL. Explosive boiling of water droplets irradiated with intense CO(2)-laser radiation: numerical experiments. APPLIED OPTICS 1994; 33:5805-5810. [PMID: 20935983 DOI: 10.1364/ao.33.005805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The results of numerical calculations of water-droplet explosions initiated by intense CO(2)-laser radiation are presented. The theoretical model for this process is based on the solution of the value of the thermal-boundary problem in an inhomogeneously heated droplet, including the kinetic equation describingvapor generation in a superheated liquid. The main characteristics of droplet explosions (e.g., degree of explosive evaporation and time of explosion) are calculated. It is established that these characteristics depend on the heating rate of the droplet and on its radius. The results point to the fact that two droplet-heating regimes can be distinguished-slow heating and rapid heating-based on the behavior of the explosive boiling process. This division represents the competition of real physical processes in an irradiated droplet and makes it possible to separate the basic, specific features of the explosion process.
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Optical and acoustic study of nucleation and growth of bubbles at a liquid-solid interface induced by nanosecond-pulsed-laser heating. ACTA ACUST UNITED AC 1994. [DOI: 10.1007/bf00323618] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Thomson DS, Murphy DM. Laser-induced ion formation thresholds of aerosol particles in a vacuum. APPLIED OPTICS 1993; 32:6818-6826. [PMID: 20856535 DOI: 10.1364/ao.32.006818] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Using a time-of-flight mass spectrometer, we have measured the threshold for producing ions from various aerosol particles in avacuum with laser radiation at 248 nm,308 nm, and 10.6µm. In addition, a limited amount of similar data were taken at 193 and 337 nm. At 10.6 µm, two thresholds were observed: one near 3 GW/cm(2), which corresponds to partial ionization, and another at 6 GW/cm(2), which we attribute to plasma formation. At 308 nm, the threshold for ion production is on the order of 200 MW/cm(2). Shorter wavelengths require even less energy, with < 100 MW/cm(2) yielding normal molecular-mass spectra and approximately 500 MW/cm(2) fragmenting the sample to atomic ions.
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Spann JF, Maloney DJ, Lawson WF, Casleton KH. Response of two-phase droplets to intense electromagnetic radiation. APPLIED OPTICS 1993; 32:2152-2158. [PMID: 20820360 DOI: 10.1364/ao.32.002152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The response of two-phase droplets to intense radiant heating is studied to determine the incident power that is required for causing explosive boiling in the liquid phase. The droplets studied consist of strongly absorbing coal particles dispersed in a weakly absorbing water medium. Experiments are performed by confining droplets (radii = 37, 55, and 80 microm) electrodynamically and irradiating them from two sides with pulsed laser beams. Emphasis is placed on the transition region from accelerated droplet vaporization to droplet superheating and explosive boiling. The time scale observed for explosive boiling is more than 2 orders of magnitude longer than published values for pure liquids. The delayed response is the result of energy transfer limitations between the absorbing solid phase and the surrounding liquid.
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Latifi H, Xie JG, Ruekgauer TE, Armstrong RL, Pinnick RG. Multiple superheating thresholds of micrometer-sized droplets irradiated by pulsed CO(2) lasers. OPTICS LETTERS 1991; 16:1129-1131. [PMID: 19776896 DOI: 10.1364/ol.16.001129] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Two distinct superheating fluence thresholds have been measured for micrometer-sized droplets of liquids irradiated by pulsed CO(2) lasers. The lower, deformation, threshold results in minimal droplet mass loss, whereas the higher, disintegration, threshold (which is well defined only if observed several tens of microseconds after the heating laser pulse) leads to droplet fragmentation into many microparticles and vapor. Deformation thresholds are nearly coincident for either long (10-micros) or short (0.4-micros) laser pulses. Disintegration thresholds are higher for long-pulse irradiation and increase with decreasing absorption. A qualitative explanation is given for these phenomena based on the effects of surface tension, thermal conduction, and thermally induced optical inhomogeneities.
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Xie J, Ruekgauer TE, Armstrong RL, Pinnick RG. Evaporative instability in pulsed laser-heated droplets. PHYSICAL REVIEW LETTERS 1991; 66:2988-2991. [PMID: 10043670 DOI: 10.1103/physrevlett.66.2988] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Schendel JS, Stickel RE, Vandijk CA, Sandholm ST, Davis DD, Bradshaw JD. Atmospheric ammonia measurement using a VUV/photo-fragmentation laser-induced fluorescence technique. APPLIED OPTICS 1990; 29:4924-4937. [PMID: 20577487 DOI: 10.1364/ao.29.004924] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Vacuum ultraviolet/photofragmentation laser-induced fluorescence has been demonstrated to be a highly specific and sensitive method for the quantitative measurement of atmospheric ammonia (NH(3)). The fluorescence detected in this approach results from the two 193-nm photon photofragmentation step NH(3)?NH(2)? NH(b(1)Sigma(+)) followed by the excitation of the NH(b(1)Sigma(+)) NH(c(1)Pi) transition via a 450-nm photon with final emission being observed from the NH(c(1) Pi) NH(a(1)Delta) transition at 325 nm. Limits of detection for the instrumentpresented here are < 10 pptv and < 4 pptv for 1- and 5-min integration periods, respectively, in ambient sampling conditions. The technique is free from interferences and system performance does not significantly degrade in adverse sampling conditions (i.e., rain, fog, clouds, haze, etc.). Spectroscopic selectivity in the NH(b(1)Sigma(+))?NH(c(1)Pi) transition is sufficient to resolve (15)NH(3) and (14)NH(3) contributions for use in atmospheric tracer studies. Average ammonia measurements at Stone Mountain, GA, ranged from approximately 110 pptv for air temperatures <5 degrees C to approximately 240 pptv for air temperatures >/=<5 degrees C over the period from Dec. 1987 to the end of Apr. 1988.
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Kwok AS, Wood CF, Chang RK. Fluorescence imaging of CO(2)laser-heated droplets. OPTICS LETTERS 1990; 15:664-666. [PMID: 19768040 DOI: 10.1364/ol.15.000664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Distortion, ejection, shattering, and propulsion of water and ethanol droplets containing Rhodamine 6G dye have been photographed at different time delays after initiation of a CO(2) laser pulse, whichcauses explosive vaporization of the droplets. We have developed a fluorescence imaging technique to photograph the liquid-phase portion of the ejected material and the parent droplet after irradiation by the CO(2) laser pulse.
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