Harry David Morgan

Total photoabsorption cross section of molecular nitrogen near 83.4 nm

The photoabsorption cross section of molecular nitrogen near 83.4 nm has been measured at room temperature. The cross sections at the wavelengths of the 2s2p4 4P5/2, 4P3/2, and 4P1/2 (all - 2s²2p³ 4So3/2) O+ emission lines are measured to be 10.1 ± 1.6 Mb, 0.29 ± 0.02 Mb, and 0.049 ± 0.008 Mb respectively. These measurements were made with an O+ emission discharge source, and repeated using a synchrotron radiation source. Both measurements were made with the 0.008-nm resolution 6.65-m spectrometer at the SURF II storage ring of the National Institute for Standards and Technology.

High resolution vuv photo-absorption cross sections of O2 near 83.4 nm

Abstract The O+ (2s2p4 4P → 2s22p3 4S0) 83.4 nm triplet is of great interest in ionosphere physics primarily for its role in remote sensing of the ionosphere. Absolute photoabsorption cross sections of O2 near 83.4 nm have been made utilizing the Very High Resolution Spectrometer at the National Institute of Standards and Technologys Synchrotron Ultraviolet Radiation Facility (SURF II). The 6.65 m spectrometer has a resolving power of ∼ 100,000 near 80 nm (FWHM = 0.8 pm). Cross sections were measured over the range 83.0 – 83.5 nm. The value of the cross sections at the positions of the triplet emission lines located at 83.4465, 83.3329, and 83.2757 nm are 14.4 ± 0.7, 18.4 ± 0.8, and 38.2 ± 1.5 Mb respectively. The cross section at the peak of the absorption band at 83.268 nm is 40.6 ± 1.6 Mb. The large discrepancies between our values and those of other investigators are probably due to their low instrumental resolution.

The very high resolution spectrometer at the National Institute of Standards and Technology

Abstract The Very High Resolution Spectrometer at the Synchrotron Ultraviolet Radiation Facility of the National Institute of Standards and Technology has been upgraded with improved beamline throughput, instrument control and data acquisition. Since this upgrade, a number of high resolution measurements have been made in the vacuum ultraviolet region of the electromagnetic spectrum between 40 nm and 100 nm. Utilizing the features of this instrument, on-line photoelectric recording at intervals of 0.1 pm in first order from a synchrotron light source can be made. A resolution of 0.9 pm has been obtained at 80 nm.