Experimental determination of the dispersion in the mean linear dipole polarizability α(ω) of small hydrocarbons and evaluation of Cauchy moments between 325 nm and 633 nm

Hohm, Uwe

doi:10.1080/00268979300100621

Cited by 34 publications

(14 citation statements)

References 45 publications

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“…2 x m2, this is a very satisfactory result, because calculation of the frequency dependence of a(w) and especially a'(w) is still very difficult. However, the zero-frequency result in this work, a'(0) = 2.04 (22) x lo-,' m2, and that of Oddershede and Svendsen9 nearly coincide and both are in very good agreement with the best ah initio calculations available today of a'(0) = 1.97 (20) x lo-,' m2 by Maroulis," using fourth-order Marller-Plesset perturbation theory.…”

Section: Discussionsupporting

confidence: 77%

Frequency dependence of the polarizability derivative [∂α(ω)/∂r]o of chlorine from temperature‐dependent gas‐phase refractive index measurements

Hohm

Trümper

1995

J Raman Spectroscopy

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The refractive index n ( o , T, p) of molecular chlorine, CI, , was measured in the ranges of temperature T between 290 and 1100 K and pressurep between lo4 and 2 x lo5 Pa and at three wavelengths k = 2rcc0/0 between 632.990 and 543.516 nm. From these measurements the frequency and temperature dependence of the mean dipole polarizability (u (o))~ of CI, was obtained. The polarizabilities were analysed according to theories of Bell and Buckingham, yielding 1 0 2 0 [~u ( o ) /~u~o / m ' = 2.02(22) + 6.27(51) x (W/S-')'for the frequency dependence of the polarizability derivative of chlorine between o = 0 and 3.5 x 10'' s-'. This result is in fair agreement with ab initio calculations, but disagrees with polarizability derivatives obtained from measurements of the differential Raman scattering cross-section.

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Section: Discussionsupporting

confidence: 77%

Frequency dependence of the polarizability derivative [∂α(ω)/∂r]o of chlorine from temperature‐dependent gas‐phase refractive index measurements

Hohm

Trümper

1995

J Raman Spectroscopy

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“…We also include collisionally-induced absorption (CIA) and Rayleigh scattering. CIA due to H 2 -H 2 , H 2 -He, and H 2 -CH 4 is taken from HITRAN (Richard et al 2012), whilst Rayleigh scattering cross section for H 2 , He, and H 2 O are derived from refractive indices in various sources (Hohm 1993;Mansfield & Peck 1969;Hill & Lawrence 1986).…”

Section: Molecular and Atomic Opacitiesmentioning

confidence: 99%

The metal-rich atmosphere of the exo-Neptune HAT-P-26b

Macdonald

Madhusudhan

2019

Monthly Notices of the Royal Astronomical Society

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Transmission spectroscopy is enabling precise measurements of atmospheric H 2 O abundances for numerous giant exoplanets. For hot Jupiters, relating H 2 O abundances to metallicities provides a powerful probe of their formation conditions. However, metallicity measurements for Neptune-mass exoplanets are only now becoming viable. Exo-Neptunes are expected to possess super-solar metallicities from accretion of H 2 O-rich and solid-rich planetesimals. However, initial investigations into the exo-Neptune HAT-P-26b suggested a significantly lower metallicity than predicted by the core-accretion theory of planetary formation and solar system expectations from Uranus and Neptune. Here, we report an extensive atmospheric retrieval analysis of HAT-P-26b, combining all available observations, to reveal its composition, temperature structure, and cloud properties. Our analysis reveals an atmosphere containing 1.5 +2.1 −0.9 % H 2 O, an O/H of 18.1 +25.9 −11.3 × solar, and C/O < 0.33 (to 2σ). This updated metallicity, the most precise exo-Neptune metallicity reported to date, suggests a formation history with significant planetesimal accretion, albeit below that of Uranus and Neptune. We additionally report evidence for metal hydrides at 4.1σ confidence. Potential candidates are identified as TiH (3.6σ), CrH (2.1σ), or ScH (1.8σ). Maintaining gas-phase metal hydrides at the derived temperature (563 +58 −54 K) necessitates strong disequilibrium processes or external replenishment. Finally, we simulate the James Webb Space Telescope Guaranteed Time Observations for HAT-P-26b. Assuming a composition consistent with current observations, we predict JWST can detect H 2 O (at 29σ), CH 4 (6.2σ), CO 2 (13σ), and CO (3.7σ), thereby improving metallicity and C/O precision to 0.2 dex and 0.35 dex, respectively. Furthermore, NIRISS observations could detect several metal hydrides at > 5σ confidence.

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“…By extrapolating Hohm's measured dynamic polarizabilities [29] to zero frequency, we have obtained an estimate for ~ of (4.5717_+ 0-0008) x 10 -4o C 2 m 2 J-1. This value compares favourably with the ab initio estimates, and has been used in all our calculations of ~.…”

Section: Molecular Properties Of Ethenementioning

confidence: 98%

“…Knowledge ofpo and 0e v allows extraction of the polarizability anisotropy through equation (29), and the polarizability anisotropy is related to the polarizability tensor components through equation (20). Solving equations (19), (20) and (49) for till, Ct2z and ct33 leads to the values listed in table 2.…”

Section: Molecular Properties Of Ethenementioning

confidence: 99%

“…Solving equations (19), (20) and (49) for till, Ct2z and ct33 leads to the values listed in table 2. In our calculations of ~ we have used the second set of values in table 2 which were obtained from our measured P0 for ethene (see section 8), the 0t v at 514.5nm interpolated from Hohm's high-precision measurements of the frequency dependence of ~v for ethene [29], and the more precise value for R20 recently obtained by Barbbs [30]. Use of the first set of values, however, sees a decrease of less than 0"5 % in the calculated ~.…”

Section: Molecular Properties Of Ethenementioning

confidence: 99%

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Calculation and measurement of the second light-scattering virial coefficients of nonlinear molecules: a study of ethene

Couling

Graham

1996

Molecular Physics

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The second light-scattering virial coefficient Bp of ethene has been extracted from measurements of the depolarization ratio p at gas pressures up to 3"2 MPa. The value calculated using our recent molecular tensor theory of Bp for axially symmetric molecules, underestimates the experimental value by 40%. A complete molecular tensor theory of Bp for nonlinear molecules is presented, and leads to a calculated value for ethene which is within 2 % of the experimental value.

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Experimental determination of the dispersion in the mean linear dipole polarizability α(ω) of small hydrocarbons and evaluation of Cauchy moments between 325 nm and 633 nm

Cited by 34 publications

References 45 publications

Frequency dependence of the polarizability derivative [∂α(ω)/∂r]o of chlorine from temperature‐dependent gas‐phase refractive index measurements

Frequency dependence of the polarizability derivative [∂α(ω)/∂r]o of chlorine from temperature‐dependent gas‐phase refractive index measurements

The metal-rich atmosphere of the exo-Neptune HAT-P-26b

Calculation and measurement of the second light-scattering virial coefficients of nonlinear molecules: a study of ethene

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