OSA's Digital Library

Applied Spectroscopy

Applied Spectroscopy

| PUBLISHED BY SAS — AVAILABLE FROM SAS AND OSA

  • Vol. 56, Iss. 8 — Aug. 1, 2002
  • pp: 1067–1081

Infrared Spectroscopic Evidence for the Ice Formation Mechanisms Active in Aerosol Flow Tubes

Hui-Ming Hung and Scot T. Martin

Applied Spectroscopy, Vol. 56, Issue 8, pp. 1067-1081 (2002)


View Full Text Article

Acrobat PDF (458 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations
  • Export Citation/Save Click for help

Abstract

Interest in quantifying processes of ice formation in the atmosphere has led to the recent development of new laboratory techniques, including an aerosol flow tube (AFT) reactor employed for the study of the ice nucleation kinetics of suspended submicrometer aqueous particles. The AFT technique employs an infrared (IR) beam along the flow tube axis. Spectral changes between 700 and 6000 cm-1 indicate the formation of ice at sufficiently cool temperatures. Apparent freezing temperatures are determined as a function of condensed-phase mole fraction composition. A typical aqueous chemical system is (NH4)2SO4/H2O. The mole fraction composition of the condensed-phase of this aerosol is determined by the ratio of the integrated spectroscopic bands for H2O and SO42-. A key uncertainty in the AFT-IR technique is the freezing mechanism, and knowledge of the mechanism is essential to estimate homogeneous nucleation rates (J, cm-3 s-1) from observed apparent freezing temperatures. The current work provides observational and modeling spectral evidence, based upon changes in the scattering component of the recorded IR extinction spectra with temperature, that observed ice freezing events at warmer temperatures arise from the following mechanism: relatively few particles in the aerosol freeze (e.g., 1 in 106) and this primary event is followed by rapid scavenging of water vapor to grow the few ice particles into large ice particles observed in the IR spectra. Correspondingly, the remaining aqueous particles partially evaporate. In contrast, the spectral evidence provides support that a modified mechanism is operative at cooler temperatures: the ice freezing event consists of the freezing of a much larger fraction of the particles (e.g., 1 in 10) accompanied by a much less important vapor-phase mass transfer event.

Citation
Hui-Ming Hung and Scot T. Martin, "Infrared Spectroscopic Evidence for the Ice Formation Mechanisms Active in Aerosol Flow Tubes," Appl. Spectrosc. 56, 1067-1081 (2002)
http://www.opticsinfobase.org/as/abstract.cfm?URI=as-56-8-1067

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Log in to access OSA Member Subscription

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited