Simulation Studies of Amide I IR Absorption and Two-Dimensional IR Spectra ofβHairpins in Liquid Water

2005 ◽  
Vol 109 (23) ◽  
pp. 11789-11801 ◽  
Author(s):  
Seungsoo Hahn ◽  
Sihyun Ham ◽  
Minhaeng Cho
Keyword(s):  
Ir Spectra ◽  
Liquid Water ◽  
Ir Absorption ◽  
Two Dimensional ◽  
Simulation Studies

scholarly journals Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

Two-Dimensional Correlation Spectroscopy (2D-COS) of Gas-Phase Pyrrole Clusters in a Supersonic Jet: Treatment of Sharp Bands on a Broad Background

2020 ◽  
Vol 74 (4) ◽  
pp. 408-416
Author(s):  
Yoshiteru Matsumoto ◽  
Souichi Tezuka
Keyword(s):  
Ir Spectra ◽  
Gas Phase ◽  
Supersonic Jet ◽  
Correlation Spectroscopy ◽  
Cavity Ringdown Spectroscopy ◽  
Two Dimensional ◽  
Cavity Ringdown ◽  
Correlation Spectrum ◽  
Large Clusters ◽  
Small Clusters

Two-dimensional correlation spectroscopy (2D-COS) is a useful technique to analyze any intensity behavior of optical spectra that exhibit a complicated feature with overlapped bands. In this study, we apply 2D-COS to the infrared (IR) spectra of gas-phase pyrrole (Py) clusters. The NH stretching vibrations of the Py clusters are measured by cavity ringdown spectroscopy. The observed IR spectra of the Py clusters consist of sharp bands, full width half-maximum (FWHM) ∼1 cm−1, and a broad background (FWHM >50 cm−1). The 2D asynchronous correlation spectra reveal that the sharp bands and a broad background are assigned to small clusters of dimer to pentamer and large clusters with bulk-like structures, respectively, which support the results of our previous study. The sharp bands are also analyzed using another 2D asynchronous correlation spectrum, which is obtained by decomposing the observed IR spectra into sharp and broad components. Because the asynchronous signals are consistent with those obtained from the IR spectra without decomposition, the result would suggest that we need not to decompose the IR spectra into sharp and broad components before applying 2D-COS. However, our model simulations of 2D-COS showed a counterexample that gives an incorrect result without removing a broad background component from the IR spectra. This study strongly suggests that we need to undertake a careful treatment of the complicated IR spectrum with various widths of bands.

IR spectra of powder hematite: effects of particle size and shape

Clay Minerals ◽  
1981 ◽  
Vol 16 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Jose L. Rendon ◽  
Carlos J. Serna
Keyword(s):  
Particle Size ◽  
Ir Spectra ◽  
Ir Absorption ◽  
Surface Mode ◽  
Absorption Bands ◽  
Size And Shape ◽  
Ir Absorption Spectra ◽  
Theoretical Predictions ◽  
Particle Size And Shape ◽  
Average Size

AbstractHematites obtained by heating goethite gave different IR absorption spectra depending on the temperature of formation. Hematites formed between 250–600°C consisted of lath-like crystals (average size 0.4 ×0.08 µm) and showed, in accordance with theoretical predictions, very similar IR spectra whose absorption bands could all be assigned to surface mode vibrations. However, significantly different IR spectra were given by hematites formed between 700–950°C, the differences being correlated with variations in the size and shape of the particles. Differences observed in the IR spectra of powder hematite do not therefore justify new names for the mineral, as have been proposed in the literature.

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