Intensity measurements of the CH4 bands in the region 4350 Å to 10,600 Å

Giver, L. P.

doi:10.1016/0022-4073(78)90064-x

Cited by 142 publications

(29 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The visible absorption spectrum of liquid methane (10,11). on the other hand, was seen to be best fit to a combination of overtones of normal modes of vibration (6,7,18). This assignment of the methane spectrum is consistent with the trend seen in the dihalomethanes (22), in which the local mode model was replaced by a normal mode model as the progression was made from heavier (CH212) to lighter (CH2F2) halogen substitutions.…”

Section: Discussionsupporting

confidence: 67%

“…As early as 1930, photographic laboratory spectra of high pressure gaseous methane, ethane, and ethylene were measured by Adel and Slipher (5) for comparison to planetary spectra in the determination of atmospheric compositions, pressures, and temperatures. Subsequently there have been improved measurements of the visible absorption spectra of methane (1,(6)(7)(8)(9)(10)(11), ethane (6), and acetylene (12); but to our knowledge no further measurement of the visible spectrum of ethylene has been made in spite of its identification in infrared planetary spectra (13) and its importance in the interpretation of the photochemistry of Jupiter's and Titan's atmospheres (4,14,15). This is in part due to the small abundances of ethylene believed to exist in these planetary atmospheres (4,16).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Visible absorption spectrum of liquid ethylene

Nelson¹,

Patel²

1981

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The visible pbsorption spectrum of liquid ethylene at -108 K from 5500 A to 7200 A was measured by using a pulsed tunable dye laser, immersed-transducer, gated-detection opto-acoustic spectroscopy technique. The absorption features show the strongest band with an absorption coefficient of m2 x 10-2 cm-' and the weakest band with an absorption coefficient of _I x 10-4 cM-. Proposed assignments of the observed absorption peaks involve combinations of overtones of local and normal modes of vibration of ethylene.The measurement of visible absorption spectra of the simple hydrocarbons methane, ethane, acetylene, and ethylene is of growing interest in the interpretation of planetary spectra and as a test of the theory of localized modes of vibration in highly vibrationally excited molecules. These gases dominate the visible and near infrared spectra of the major planets (1), with abundances decreasing in approximately the order listed (2-4). As early as 1930, photographic laboratory spectra of high pressure gaseous methane, ethane, and ethylene were measured by Adel and Slipher (5) for comparison to planetary spectra in the determination of atmospheric compositions, pressures, and temperatures. Subsequently there have been improved measurements of the visible absorption spectra of methane (1, 6-11), ethane (6), and acetylene (12); but to our knowledge no further measurement of the visible spectrum of ethylene has been made in spite of its identification in infrared planetary spectra (13) and its importance in the interpretation of the photochemistry of Jupiter's and Titan's atmospheres (4,14,15). This is in part due to the small abundances of ethylene believed to exist in these planetary atmospheres (4, 16). Because of the dense spacing of vibrational-rotational lines within the absorption bands of methane (6, 9, 17) the effects of pressure broadening are minimized (18), and the liquid absorption spectrum of methane has been shown to follow the high pressure gas absorption spectrum with small systematic shifts in band frequencies and asymmetries in band shapes (10,11). This may allow the laboratory spectrum of liquid ethylene reported here to be used as an approximation for the planetary spectrum.We recently have shown that pulsed opto-acoustic (OA) spectroscopy is a superior technique for the measurement of the weak visible absorption bands of liquid methane (11), and we have used the same technique here to measure what we believe to be the first visible absorption spectrum of liquid ethylene. The spectrum is strikingly similar to the liquid methane spectrum, continuing a correlation that has been observed between the visible methane and ethane spectra (6). Adel and Slipher (5) could report only a single gas phase ethylene absorption band within the spectral region of our measurements at an abundance of 1.8 km-amagat. At an equivalent abundance of 10-2 km-amagat we have observed eight well-resolved bands.The simplicity of vibrational overtone spectra of benzene led Henry and Siebrand (19) to propose that th...

show abstract

Section: Discussionsupporting

confidence: 67%

mentioning

confidence: 99%

Visible absorption spectrum of liquid ethylene

Nelson¹,

Patel²

1981

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…This band has been observed in all the giant planets and in Titan's spectrum and it appears in other previously published spectra of Eris, but has not been discussed. The band has been assigned to CH 4 in its gaseous (Giver 1978) and liquid (Ramaprasad et al 1978;Patel et al 1980) phases in laboratory experiments. The band strength is ∼1 order of magnitude smaller than the 730 nm band, thus, its appearance certainly suggests relatively long path-lengths, and likely high concentrations of CH 4 .…”

Section: Spectroscopic Analysismentioning

confidence: 98%

The spectrum of (136199) Eris between 350 and 2350 nm: results with X-Shooter

Álvarez-Candal

Pinilla-Alonso

Licandro

et al. 2011

A&A

View full text Add to dashboard Cite

Context. X-Shooter is the first second-generation instrument for the ESO-Very Large Telescope. It is a spectrograph covering the entire 300−2480 nm spectral range at once with a high resolving power. These properties enticed us to observe the well-known transNeptunian object (136199) Eris during the science verification of the instrument. The target has numerous absorption features in the optical and near-infrared domain that have been observed by different authors, showing differences in these features' positions and strengths. Aims. Besides testing the capabilities of X-Shooter to observe minor bodies, we attempt to constrain the existence of super-volatiles, e.g., CH 4 , CO and N 2 , and in particular we try to understand the physical-chemical state of the ices on Eris' surface. Methods. We observed Eris in the 300−2480 nm range and compared the newly obtained spectra with those available in the literature. We identified several absorption features, measured their positions and depth, and compare them with those of the reflectance of pure methane ice obtained from the optical constants of this ice at 30 K to study shifts in these features' positions and find a possible explanation for their origin. Results. We identify several absorption bands in the spectrum that are all consistent with the presence of CH 4 ice. We do not identify bands related to N 2 or CO. We measured the central wavelengths of the bands and compared to those measured in the spectrum of pure CH 4 at 30 K finding variable spectral shifts. Conclusions. Based on these wavelength shifts, we confirm the presence of a dilution of CH 4 in other ice on the surface of Eris and the presence of pure CH 4 that is spatially segregated. The comparison of the centers and shapes of these bands with previous works suggests that the surface is heterogeneous. The absence of the 2160 nm band of N 2 can be explained if the surface temperature is below 35.6 K, the transition temperature between the alpha and beta phases of this ice. Our results, including the reanalysis of data published elsewhere, point to a heterogeneous surface on Eris.

show abstract

“…Giver 1978), and observed spectra of the giant planets in the Solar System by Karkoschka (1998). These works focus on the lowresolution shape of the methane absorption bands.…”

Section: Methanementioning

confidence: 99%

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

Lovis

Snellen

Mouillet

et al. 2017

A&A

159

147

View full text Add to dashboard Cite

Context. The temperate Earth-mass planet Proxima b is the closest exoplanet to Earth and represents what may be our best ever opportunity to search for life outside the Solar System. Aims. We aim at directly detecting Proxima b and characterizing its atmosphere by spatially resolving the planet and obtaining high-resolution reflected-light spectra. Methods. We propose to develop a coupling interface between the SPHERE high-contrast imager and the new ESPRESSO spectrograph, both installed at ESO VLT. The angular separation of 37 mas between Proxima b and its host star requires the use of visible wavelengths to spatially resolve the planet on a 8.2-m telescope. At an estimated planet-to-star contrast of ∼ 10 −7 in reflected light, Proxima b is extremely challenging to detect with SPHERE alone. However, the combination of a ∼10 3 -10 4 contrast enhancement from SPHERE to the high spectral resolution of ESPRESSO can reveal the planetary spectral features and disentangle them from the stellar ones. Results. We find that significant but realistic upgrades to SPHERE and ESPRESSO would enable a 5-σ detection of the planet and yield a measurement of its true mass and albedo in 20-40 nights of telescope time, assuming an Earth-like atmospheric composition. Moreover, it will be possible to probe the O 2 bands at 627, 686 and 760 nm, the water vapour band at 717 nm, and the methane band at 715 nm. In particular, a 3.6-σ detection of O 2 could be made in about 60 nights of telescope time. Those would need to be spread over 3 years considering optimal observability conditions for the planet. Conclusions. The very existence of Proxima b and the SPHERE-ESPRESSO synergy represent a unique opportunity to detect biosignatures on an exoplanet in the near future. It is also a crucial pathfinder experiment for the development of Extremely Large Telescopes and their instruments, in particular the E-ELT and its high-resolution visible/near-IR spectrograph.

show abstract

Intensity measurements of the CH4 bands in the region 4350 Å to 10,600 Å

Cited by 142 publications

References 18 publications

Visible absorption spectrum of liquid ethylene

Visible absorption spectrum of liquid ethylene

The spectrum of (136199) Eris between 350 and 2350 nm: results with X-Shooter

Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

Contact Info

Product

Resources

About