Edward K. Damon

Mid-infrared filters using conducting elements

This paper presents measured data on mid-infrared filters using conducting elements based on a simple first-order design philosophy. To the best of our knowledge, the filter center frequencies are at least a factor of 10 higher than any previously reported. The use of conducting elements adds an additional degree of freedom, which may be exploited to obtain filter characteristics superior to simple multilayer dielectric filters.

Water vapor–nitrogen absorption at CO 2 laser frequencies

In this paper we report the results of a series of pressure-broadened water vapor absorption measurements at 27 CO(2) laser frequencies between 935 cm(-1) and 1082 cm(-1). Both multiple traversal cell and optoacoustic (spectrophone) techniques were utilized together with an electronically stabilized cw CO(2) laser. Comparison of the results obtained by these two methods shows remarkable agreement, indicating a precision which has not been previously achieved in pressure-broadened studies of water vapor. The data of 10.59 microm substantiate the existence of the large (>200) self-broadening coefficients determined in an earlier study by McCoy. In this work we have treated the case of water vapor in N(2) at a total pressure of 1 atm. We have also studied water vapor in air and will report those results separately.

Effects of Oxygen Addition on Pressure-Broadened Water-Vapor Absorption in the 10-Micrometer region,

We have measured the monochromatic transmittances of pressure-broadened room-temperature water vapor samples at five laser frequencies of the CO(2) laser in the 10.4-microm band. Three different buffer gases were used. They were pure nitrogen, an 80:20 mixture of nitrogen and oxygen, and a 60:40 mixture of nitrogen and oxygen. The measurements at the five laser lines imply that oxygen is a less efficient broadener than nitrogen. The ratio of the oxygen-broadening coefficient to the nitrogen-broadening coefficient was measured to be 0.75 based on the data at the R(20) laser line. Results of this study demonstrate that pure nitrogen should not be used as a broadener for atmospheric modeling of monochromatic transmittances in the laboratory.

The efficiency of the phosphorescence decay of the isolated SO2(3B1) molecule

Abstract The phosphorescence decay kinetics of SO 2 ( 3 B 1 ) molecules have been studied using laser excitation at discrete wave-lengths within both the first-allowed singlet and the “forbidden” triplet bands of SO 2 . The estimated collision-free lifetime of SO 2 ( 3 B 1 ) molecules (8.1 ± 2.5 ms) is considerably longer than that reported from previous studies in which both unidentified pressure saturation effects on SO 2 ( 3 B 1 ) quenching and diffusional loss of triplets led to anomalously short lifetime estimates. Both the lifetime and the bimolecular SO 2 ( 3 B 1 ) quenching rate constant with SO 2 , (4.2 ± 0.1) × 10 8 Q mole t− s −1 , are independent of the excitation wavelength within the limit of the experimental error. The new lifetime determination, coupled with our previous measurements of the relative phosphorescence intensities of biacetyl and SO 2 excited at 3829 A, leads to a new estimate of the SO 2 ( 3 B 1 ) phosphorescence quantum yield at zero pressure: φ 0 P = 0.95 ± 0.29. The lifetime estimate and integrated SO 2 ( 3 B 1 ) ← SO 2 (X∼ 1 A 1 ) band absorption data confirm the high efficiency of the radiative decay path of SO 2 ( 3 B 1 ) excited at very low pressures. Thus the apparent anomaly of the previously observed and theoretically unexpected importance of non-radiative decay in the isolated simple triatomic SO 2 ( 3 B 1 ) molecules is removed.

On the pressure saturation effect of the quenching of SO2(3B1) molecules

Abstract The phosphorescent lifetimes of SO2(3B1) molecules have been studied at excitation wavelength 2662 and 3631 A under high pressure conditions (1 torr ⩽ P ⩽ 400 torr) in the presence of foreign gases (CO2, CO and N2). The pressure saturation effect, which was found recently by Rudolph and Strickler, is confirmed. A mathematical formulation of the experimental results is suggested to fit all the data.

Vibronic effects in the decay of the fluorescence excited in SO2 and NO2

Abstract The intensity of fluorescence of the first excited singlet sulphur dioxide molecule ( 1 SO 2 ) shows an unexpected non-exponential decay when observed over several lifetimes. This is found for both broad-band, Xe-flash excitation at 2660 ± 100 and 2860 ± 160 A and for laser excitation at 2662 ± 1 A. The decay is exponential when either long wavelength, broad-band excitation is employed (2980 ± 140 A) or at long observation times using any excitation wavelength. All of the data are most consistent with the hypothesis of one emitting singlet state whose rate constants are somewhat dependent on its degree of vibrational excitation. A kinetic treatment of the data gives the zero pressure lifetime and the quenching rate constants for the vibrationally rich (22.7 kcal/mole) and the vibrationally relaxed excited singlet states. These and other quantum yield data suggest that the observed decrease in the lifetime of the 1 SO 2 state which accompanies vibrational relaxation is associated with a significant increase in the rate of some ill-defined, non-radiative decay process for these conditions. Emission data from the spectroscopically analogous compound NO 2 , excited at 4365, 5324, and 6943 A, also show non-exponential decay. In this case, however, the lifetimes at zero pressure show no significant variation with alteration in the degree of vibrational excitation of the NO 2 ( 2 B 1 ) state.