Publication Abstracts

Ho 1966

Ho, W.W.-Y., 1966: The Atmosphere of Venus. Ph.D. thesis. Columbia University.

Pressure-induced absorption in CO2 has been studied at a frequency of 9260 Me/sec over a temperature range from 273°K to 500°K and to pressures as high as 95 atm. Mixture CO2 and N2 have been studied for eight different concentrations of CO2 from 240°K to 500°K and to pressures up to 130 atm. Sample mixtures consisting of approximately 10% CO2-90% A and 10% CO2-90% Ne were also studied.

The dielectric loss, ε″, for pure gases was fitted with an expression consisting of a series expansion in the amagat density ρ of the form,

ε″/νi̅ρ = A1ρ + A2ρ2 + ...

here ν̅ is the frequency in wave numbers.

For pure CO2, it was found that A1 = 2.5(1)×10-8(T/273)-3.0(l),

A2/A1 = -1.05(8)×l0-2(T/273)-2.3(3),

where the temperature T is in degrees Kelvin, and for N2,

A1 = 0.014(2)×10-8(T/273)-2.8(3).

The coefficient A1 is interpreted as the contribution due to transient dipole moments induced by the quadrupole field of the molecules in a binary encounter, and similarly A2 is that due to effects of ternary interactions. Terms of higher order could not be determined because of the limit in sensitivity of the_experiment, and A2 was only measured for pure CO2.

Calculations of the molecular quadrupole moment from the first coefficient A1 of the dielectric loss yielded the results,

QCO2 = 5.8×l0-26 esu,

QN2 = 0.9×l0-26 esu.

It was found experimentally that the dielectric loss for gas mixtures consisting of CO2, N2, A, and Ne can be expressed in the form, correct to ρ2, by

ε″/ν̅ρT2 = Sum(i-1,N) Sum(j≤1) Aij fi fj,

where ρT is the total density in amagat units, fi is the molar fraction for gas i, Aii is the self-loss coefficients for pure gases, and Aij is the cross term corresponding to binary interactions of two dissimilar molecules.

The self loss of A and Ne are zero to order ρ2, and the cross terms are found to be

ACO2-N2 = 0.62(4)(T/273)-2.7(2)×10-8,

ACO2-A = 0.42(4)(T/273)-2.5(2)×10-8,

ACO2-Ne ≤ 4×10-10 at 273 K.

For purpose of calculating the microwave opacity of the Venus atmosphere, the absorption coefficient α for a mixture of CO2, N2, A, and Ne may be approximated by the following expression which is faithful to the laboratory data to within a few percent ever the range of pressures and temperatures relevant to Venus:

α = Pt2ν̅2(T/273)-5(15.7 fCO22 + 3.90 fCO22fN2 + 2.64 fCO22fA + 0.085 fN22) ×10-8/cm,

where Pt is the total pressures in atmospheres.

Applications of the experimental results to the atmosphere of Venus, under the assumption that the opacity of the atmosphere is mainly due to pressure-induced absorption, show that the frequency dependence of the observed radiofrequency emission from the planet can be well explained by model atmospheres consisting of dilute concentrations of CO2, where the surface pressure is in the range of 100 to 300 terrestrial atmospheres.

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BibTeX Citation

  author={Ho, W. W.-Y.},
  title={The Atmosphere of Venus},
  school={Columbia University},
  address={New York},

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RIS Citation

ID  - ho07500f
AU  - Ho, W. W.-Y.
PY  - 1966
BT  - The Atmosphere of Venus
PB  - Columbia University
CY  - New York
ER  -

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