The development and deployment of a ground-based, laser-induced fluorescence instrument for the in situ detection of iodine monoxide radicals.

High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer. Of particular interest are the roles IO plays in the formation of new particles in coastal marine environments and in depletion episodes of ozone and mercury in the Arctic polar spring. This paper describes a ground-based instrument that measures IO at mixing ratios less than one part in 10(12).

A new cavity based absorption instrument for detection of water isotopologues in the upper troposphere and lower stratosphere.

We describe here the Harvard integrated cavity output spectroscopy (ICOS) isotope instrument, a mid-IR infrared spectrometer using ICOS to make in situ measurements of the primary isotopologues of water vapor (H(2)O, HDO, and H(2) (18)O) in the upper troposphere and lower stratosphere (UTLS). The long path length provided by ICOS provides the sensitivity and accuracy necessary to measure these or other trace atmospheric species at concentrations in the ppbv range. The Harvard ICOS isotope instrument has been integrated onto NASA's WB-57 high-altitude research aircraft and to date has flown successfully in four field campaigns from winter 2004-2005 to the present.

Airborne interferometer for atmospheric emission and solar absorption.

The interferometer for emission and solar absorption (INTESA) is an infrared spectrometer designed to study radiative transfer in the troposphere and lower stratosphere from a NASA ER-2 aircraft. The Fourier-transform spectrometer (FTS) operates from 0.7 to 50 mum with a resolution of 0.

Ultrasensitive absorption spectroscopy with a high-finesse optical cavity and off-axis alignment.

A simple and easy to use method that allows high-finesse optical cavities to be used as absorption cells for spectroscopic purposes is presented. This method introduces a single-mode continuous-wave laser into the cavity by use of an off-axis cavity alignment geometry to eliminate systematically the resonances commonly associated with optical cavities, while preserving the absorption signal amplifying properties of such cavities. This considerably reduces the complexity of the apparatus compared with other high-resolution cavity-based absorption methods.

Channel electron multipliers: detection efficiencies with opaque MgF(2) photocathodes at XUV wavelengths.

The detection efficiencies of channel electron multipliers with opaque MgF(2) photocathodes have been measured at wavelengths between 44 A and 900 A. Efficiencies a factor of 2 greater than those of uncoated channel electron multipliers were obtained over the wavelength range from 50 A to 350 A. The absolute detection efficiencies were greater than 10% in the range from 67 A to 990 A for photocathodes illuminated at an angle of incidence of 45 degrees , with additional increases in sensitivity being obtained at short wavelengths using higher angles of incidence.