Robert L. Poynter

Submillimeter, millimeter, and microwave spectral line catalog.

This paper describes a computer accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10,000 GHz (i.e., wavelengths longer than 30 μm). The catalog can be used as a planning guide or as an aid in identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalog has been constructed by using theoretical least-squares fits of published spectra lines to accepted molecular models. The associated predictions and their estimated errors are based on the resultant fitted parameters and their covariances.

AFGL trace gas compilation: 1982 version

The new edition of the AFGL trace gas compilation is described. The latest version provides the necessary parameters for the computation of absorption or emission spectra of major bands of twenty-one gases in the region from 0 to 10,000 cm−1. Emphasis on this edition has been on the addition of numerous millimeter and submillimeter transitions, the inclusion of bands of significance in upper atmospheric processes, and strong IR bands of trace constituents likely to be used for remote detection. The sources for the additions and modifications of the absorption parameters are summarized.

Voyager 2 plasma wave observations at Saturn

The first inbound Voyager 2 crossing of Saturns bow shock [at 31.7 Saturn radii (RS), near local noon] and the last outbound crossing (at 87.4 RS, near local dawn) had similar plasma wave signatures. However, many other aspects of the plasma wave measurements differed considerably during the inbound and outbound passes, suggesting the presence of effects associated with significant north-south or noon-dawn asymmetries, or temporal variations. Within Saturns magnetosphere, the plasma wave instrument detected electron plasma oscillations, upper hybrid resonance emissions, half-gyrofrequency harmonics, hiss and chorus, narrowband electromagnetic emissions and broadband Saturn radio noise, and noise bursts with characteristics of static. At the ring plane crossing, the plasma wave instrument also detected a large number of intense impulses that we interpret in terms of ring particle impacts on Voyager 2.

First Plasma Wave Observations at Uranus

Radio emissions from Uranus were detected by the Voyager 2 plasma wave instrument about 5 days before closest approach at frequencies of 31.1 and 56.2 kilohertz. About 10 hours before closest approach the bow shock was identified by an abrupt broadband burst of electrostatic turbulence at a radial distance of 23.5 Uranus radii. Once Voyager was inside the magnetosphere, strong whistler-mode hiss and chorus emissions were observed at radial distances less than about 8 Uranus radii, in the same region where the energetic particle instruments detected intense fluxes of energetic electrons. Various other plasma waves were also observed in this same region. At the ring plane crossing, the plasma wave instrument detected a large number of impulsive events that are interpreted as impacts of micrometer-sized dust particles on the spacecraft. The maximum impact rate was about 30 to 50 impacts per second, and the north-south thickness of the impact region was about 4000 kilometers.

Voyager Planetary Radio Astronomy at Neptune

Detection of very intense short radio bursts from Neptune was possible as early as 30 days before closest approach and at least 22 days after closest approach. The bursts lay at frequencies in the range 100 to 1300 kilohertz, were narrowband and strongly polarized, and presumably originated in southern polar regions ofthe planet. Episodes of smooth emissions in the frequency range from 20 to 865 kilohertz were detected during an interval of at least 10 days around closest approach. The bursts and the smooth emissions can be described in terms of rotation in a period of 16.11 � 0.05 hours. The bursts came at regular intervals throughout the encounter, including episodes both before and after closest approach. The smooth emissions showed a half-cycle phase shift between the five episodes before and after closest approach. This experiment detected the foreshock of Neptunes magnetosphere and the impacts of dust at the times of ring-plane crossings and also near the time of closest approach. Finally, there is no evidence for Neptunian electrostatic discharges.

Microwave Spectrum, Quadrupolar Coupling Constants, and Dipole Moment of Chlorobenzene

The microwave spectrum of chlorobenzene has been observed in the frequency range between 8000 and 30 000 Mc/sec. An analysis of this spectrum gives the following values for the rotational constants for the two isotopic species, C6H5Cl35 and C6H5Cl37; A=5672.951 Mc/sec, B=1576.774 Mc/sec, C=1233.672 Mc/sec for the Cl35 isotopic species and A=5672.530 Mc/sec, B=1532.790 Mc/sec, C=1206.571 Mc/sec for the Cl37 isotopic species. The quadrupolar coupling constants which were obtained from the quadrupolar hyperfine structure are eqQ=—71.10 Mc/sec for Cl35 and eqQ=—56.10 Mc/sec for the Cl37. The quadrupolar asymmetry parameter η cannot be determined from the microwave spectrum. The observed dipole moment is 1.78±0.06 D.

Microwave Spectrum, Structure, and Dipole Moment of 2,4‐Dicarbaheptaborane (7)

The microwave spectra of all monosubstituted carbon and boron isotopic forms, and one disubstituted boron isotopic form of 2,4‐dicarbaheptaborane(7) have been analyzed. The skeletal boron and carbon atomic coordinates determined from the rotational constants show that the molecule is a pentagonal bipyramid. The two carbon atoms lie in the pentagonal base plane and are separated by one boron atom. The two apex boron atoms appear to lie on, or very near the C axis which is perpendicular to the pentagonal base. A molecular‐dipole moment of 1.32±0.03 D is oriented along the planar symmetry axis.

The microwave absorption of SO2 in the Venus atmosphere

Sulfur dioxide has a strong and complex rotational spectrum in the microwave and far infrared regions. The microwave absorption due to SO2 in a CO2 mixture is calculated for conditions applicable to the Venus atmosphere. It is shown that at the concentrations detected by Pioneer-Venus in situ measurements, SO2 may be expected to contribute significantly to the microwave opacity of the Venus atmosphere. In particular, SO2 might provide the major source of opacity in the atmospheric region immediately below the main sulfuric acid cloud deck. The spectrum is largely nonresonant at the pressures where SO2 is expected to occur, however.

SKELETAL MOLECULAR STRUCTURE OF CLOSO-2,3-DICARBAHEXABORANE(6) FROM MICROWAVE SPECTRAL STUDIES.

The microwave spectra of 13 isotopic species of closo‐2,3‐dicarbahexaborane(6) have been studied. From these results, the cage structure of this molecule has been determined. The accuracy of the molecular structure has been evaluated. The bond lengths determined were: BondLengthB(1)–B(6)2.434 ± 0.005 AC(2)–B(4)2.297 ± 0.005 AB(1)–B(4)1.721 ± 0.015 AB(4)–B(5)1.752 ± 0.005 AB(4)–C(3)1.605 ± 0.005 AC(2)–C(3)1.540 ± 0.005 AB(1)–C(2)1.627 ± 0.015 A The measured dipole moment was 1.50 ± 0.03 D.

Jupiter's microwave spectrum: implications for the upper atmosphere

It is shown through the use of weighting functions that Jupiter’s brightness temperature in the wavelength range 0.8–1.5 cm contains information on the thermal structure and abundance of ammonia in and above the tropopause in Jupiter’s atmosphere. We present new data of Jupiter’s brightness temperature in this wavelength range, and compare the results with theoretical spectra. The pressure in the Jovian atmosphere is estimated from these data to be 0.48 atm at 130K.