24 results on '"Wehr, R."'
Search Results
2. An improved isotopic method for partitioning net ecosystem–atmosphere CO2 exchange
- Author
-
Wehr, R. and Saleska, S.R.
- Published
- 2015
- Full Text
- View/download PDF
3. Seasonality of temperate forest photosynthesis and daytime respiration
- Author
-
Wehr, R., Munger, J. W., McManus, J. B., Nelson, D. D., Zahniser, M. S., Davidson, E. A., and Wofsy, S. C.
- Subjects
Carbon cycle (Biogeochemistry) -- Research ,Ecological research ,Photosynthesis -- Research ,Deciduous forests -- Environmental aspects ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
Climate models require an understanding of ecosystem-scale respiration and photosynthesis, yet there is no way of measuring these two fluxes directly; here, new instrumentation is used to determine these fluxes in a temperate forest, showing, for instance, that respiration is less during the day than at night. Seasonal variation in forest productivity Much of the carbon dioxide emitted into the atmosphere is taken up by forest ecosystems. Forest carbon sink estimates are based on the idea that ecosystem respiration is greater during the day than at night and that the efficiency of photosynthetic light use declines after spring. Rick Wehr et al. determine ecosystem photosynthesis and daytime respiration in a temperate deciduous forest over a three-year period on the basis of the isotopic composition of net ecosystem exchange. The work reveals that ecosystem respiration is in fact lower during the day than at night -- evidence of the inhibition of leaf respiration by light (the Kok effect) at the ecosystem scale. The authors argue that current approaches for estimating photosynthesis and daytime respiration do not take this effect into account and therefore overestimate ecosystem photosynthesis and daytime respiration at their forest site, and portray ecosystem photosynthetic light-use efficiency as declining when it is in fact stable. The findings may have implications for estimates of biospheric productivity and carbon cycle-climate interactions. Terrestrial ecosystems currently offset one-quarter of anthropogenic carbon dioxide (CO.sub.2) emissions because of a slight imbalance between global terrestrial photosynthesis and respiration.sup.1. Understanding what controls these two biological fluxes is therefore crucial to predicting climate change.sup.2. Yet there is no way of directly measuring the photosynthesis or daytime respiration of a whole ecosystem of interacting organisms; instead, these fluxes are generally inferred from measurements of net ecosystem-atmosphere CO.sub.2 exchange (NEE), in a way that is based on assumed ecosystem-scale responses to the environment. The consequent view of temperate deciduous forests (an important CO.sub.2 sink) is that, first, ecosystem respiration is greater during the day than at night; and second, ecosystem photosynthetic light-use efficiency peaks after leaf expansion in spring and then declines.sup.3, presumably because of leaf ageing or water stress. This view has underlain the development of terrestrial biosphere models used in climate prediction.sup.4,5 and of remote sensing indices of global biosphere productivity.sup.5,6. Here, we use new isotopic instrumentation.sup.7 to determine ecosystem photosynthesis and daytime respiration.sup.8 in a temperate deciduous forest over a three-year period. We find that ecosystem respiration is lower during the day than at night--the first robust evidence of the inhibition of leaf respiration by light.sup.9,10,11 at the ecosystem scale. Because they do not capture this effect, standard approaches.sup.12,13 overestimate ecosystem photosynthesis and daytime respiration in the first half of the growing season at our site, and inaccurately portray ecosystem photosynthetic light-use efficiency. These findings revise our understanding of forest-atmosphere carbon exchange, and provide a basis for investigating how leaf-level physiological dynamics manifest at the canopy scale in other ecosystems., Author(s): R. Wehr [sup.1] , J. W. Munger [sup.2] , J. B. McManus [sup.3] , D. D. Nelson [sup.3] , M. S. Zahniser [sup.3] , E. A. Davidson [sup.4] , [...]
- Published
- 2016
- Full Text
- View/download PDF
4. Long-term eddy covariance measurements of the isotopic composition of the ecosystem–atmosphere exchange of CO2 in a temperate forest
- Author
-
Wehr, R., Munger, J.W., Nelson, D.D., McManus, J.B., Zahniser, M.S., Wofsy, S.C., and Saleska, S.R.
- Published
- 2013
- Full Text
- View/download PDF
5. Measuring the sound absorption properties of noise barriers with inverse filtered maximum length sequences
- Author
-
Wehr, R., Haider, M., Conter, M., Gasparoni, S., and Breuss, S.
- Published
- 2013
- Full Text
- View/download PDF
6. The impact theory of spectral line shapes: a paradigm shift
- Author
-
May, A.D., Liu, W.-K., McCourt, F.R.W., Ciurylo, R., Stoker, J. Sanchez- Fortun, Shapiro, D., and Wehr, R.
- Subjects
Collisions (Nuclear physics) -- Research ,Statistical mechanics -- Research ,Quantum theory -- Research ,Physics - Abstract
An overview of the binary collision impact theory of spectral line shapes has been given to provide a unified statistical mechanical approach to line-shape theory, laser theory, nonlinear optics, and transport phenomena in dilute gases. The computation of spectral line profiles corresponding to those obtained from ultra-high-resolution spectral line-shape measurements requires numerical ab initio calculation of scattering amplitudes directly from the underlying dynamics of collisions between radiatively active molecules and their perturbers. The Wigner distribution function-density matrix is utilized to describe the kinetic theory of spectral line shapes and to discuss the various collisional processes that contribute to the kernel of kinetic equations. The influence of features of the potential energy surface on spectral parameters is also discussed, and the importance of comparing experimental line profiles directly with numerically computed line shapes obtained from reliable interaction potentials is emphasized. This contrasts sharply with the universal practice of comparing experimental line widths and shifts using some average or approximate theoretical scattering cross- sections and it contrasts sharply with fitting experimental profiles to some convenient analytical line-shape model; hence the phrase 'a paradigm shift' in the title of this work. PACS Nos.: 32.70.Jz, 33.20.-t, 33.70.Gj, 34.50.-s. Nous avons presente une revue de la theorie du profile de raies spectrales suite a des collisions binaires, de facon a developper une approche unifiee de mecanique statistique pour la theorie du profile de raie, l'optique non lineaire, la theorie des lasers et les phenomenes de transport dans les gaz dilues. Le calcul du profil des raies spectrales qui correspondent a ces mecanismes exige un calcul ab initio des amplitudes de diffusion directement a partir de la dynamique des collisions entre des molecules a impact radiatif et les mecanismes perturbateurs. Nous couplons la fonction de distribution de Wigner et la matrice de densite pour decrire la theorie cinetique du profile de raie spectrale et discuter les differents mecanismes de collision qui contribuent au noyau des equations cinetiques. Nous analysons egalement l'influence des particularites de la surface d'energie sur les parametres spectraux et nous insistons sur l'importance de comparer les profiles experimentaux de raie directement avec les profiles de raie calcules a partir de potentiels fiables. Ceci contraste nettement avec la pratique universelle ou on compare les valeurs experimentales des largeurs et deplacements de raie en utilisant des sections efficaces approximatives quelconques, theoriques ou moyennes et contraste nettement avec l'ajustement des profiles de raie experimentaux a une forme analytique commode; d'ou l'expression << un changement de paradigm >> dans le titre. [Traduit par la Redaction], 1. Introduction The impact theory of spectral line shapes has been around for about a century, beginning with the classical theory of Lorentz [1], and was essentially completed with the [...]
- Published
- 2013
- Full Text
- View/download PDF
7. Design of a difference-frequency infrared laser spectrometer for absorption line-shape studies
- Author
-
Wehr, R., Drummond, J.R., and May, A.D.
- Subjects
Atmospheric gases -- Optical properties ,Optical spectrometers -- Design and construction ,Astronomy ,Physics - Abstract
An infrared laser spectrometer based on difference-frequency generation in LiI[O.sub.3] is described. The spectrometer has a frequency uncertainty of less than 1 MHz and a signal-to-noise ratio between 3000:1 and 10,000:1. These properties allow the spectrometer to be used for studies of the non-Lorentzian and non-Voigt character of absorption line shapes in atmospheric trace gases. OCIS codes: 300.1030, 300.6190, 300.6320, 300.6340, 300.6360, 300.6390.
- Published
- 2007
8. Dicke-narrowed spectral line shapes of CO in Ar: Experimental results and a revised interpretation
- Author
-
Wehr, R., Ciuryło, R., Vitcu, A., Thibault, F., Drummond, J.R., and May, A.D.
- Published
- 2006
- Full Text
- View/download PDF
9. Collisional line shifting and broadening in the fundamental P-branch of CO in Ar between 214 and 324 K
- Author
-
Wehr, R., Vitcu, A., Thibault, F., Drummond, J.R., and May, A.D.
- Published
- 2006
- Full Text
- View/download PDF
10. Broadening, shifting, and line mixing in the 03 10 ← 01 10 parallel Q branch of N 2O
- Author
-
Vitcu, A., Ciurylo, R., Wehr, R., Drummond, J.R., and May, A.D.
- Published
- 2004
- Full Text
- View/download PDF
11. Optical feedback cavity-enhanced absorption spectroscopy for in situ measurements of the ratio 13C:12C in CO2
- Author
-
Wehr, R., Kassi, S., Romanini, D., and Gianfrani, L.
- Published
- 2008
- Full Text
- View/download PDF
12. Shifting and broadening in the fundamental band of CO highly diluted in He and Ar: A comparison with theory.
- Author
-
Luo, Caiyan, Wehr, R., Drummond, J. R., May, A. D., Thibault, F., Boissoles, J., Launay, J. M., Boulet, C., Bouanich, J.-P., and Hartmann, J.-M.
- Subjects
- *
CARBON monoxide , *DILUTION - Abstract
We present measurements of the shifts and widths of the rovibrational lines of the fundamental band of CO highly diluted in He and Ar at 296 K. The shifts are decomposed into parts odd and even in the line number, m. These are then compared with close coupled calculations carried out with the best known interaction potentials. There is general agreement between the calculated and measured values of the broadening and shifting. Furthermore, the results illustrate that the decomposition of the shifts into parts, odd and even in m, is a powerful tool for separating out the relative contributions of the isotropic and anisotropic part of the interaction to the shifts and which part needs to be corrected if there is a discrepancy. Thus, shift measurements can be added to the list of experiments that may be used to determine reliable interaction potentials. The results also show, given a potential, that close coupled calculations are accurate and could be used to confirm or establish empirical models of the temperature dependence of the broadening or shifting, etc. Such modeling is important at atmospheric physics. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]
- Published
- 2001
- Full Text
- View/download PDF
13. Spatiotemporal Controls on Observed Daytime Ozone Deposition Velocity Over Northeastern U.S. Forests During Summer.
- Author
-
Fiore, A. M., Clifton, O. E., Munger, J. W., and Wehr, R.
- Subjects
OZONE layer depletion ,VELOCITY ,SPATIOTEMPORAL processes ,ECOSYSTEMS ,FORESTS & forestry - Abstract
Spatiotemporal variability in ozone dry deposition is often overlooked despite its implications for interpreting and modeling tropospheric ozone concentrations accurately. Understanding the influences of stomatal versus nonstomatal deposition processes on ozone deposition velocity is important for attributing observed changes in the ozone depositional sink and associated damage to ecosystems. Here, we aim to identify the stomatal versus nonstomatal deposition processes driving observed variability in ozone deposition velocity over the northeastern United States during June–September. We use ozone eddy covariance measurements from Harvard Forest in Massachusetts, which span a decade, and from Kane Experimental Forest in Pennsylvania and Sand Flats State Forest in New York, which span one growing season each, along with observation‐driven modeling. Using a cumulative precipitation indicator of soil wetness, we infer that high soil uptake during dry years and low soil uptake during wet years may contribute to the twofold interannual variability in ozone deposition velocity at Harvard Forest. We link stomatal deposition and humidity to variability in ozone deposition velocity on daily timescales. The humidity dependence may reflect higher uptake by leaf cuticles under humid conditions, noted in previous work. Previous work also suggests that uptake by leaf cuticles may be enhanced after rain, but we find that increases in ozone deposition velocity on rainy days are instead mostly associated with increases in stomatal conductance. Our analysis highlights a need for constraints on subseasonal variability in ozone dry deposition to soil and fast in‐canopy chemistry during ecosystem stress. Key Points: Stomatal and cuticular deposition are inferred as drivers of day‐to‐day variability in deposition velocityHigher stomatal uptake increases deposition velocity on rainy daysObserved interannual variability at Harvard Forest may reflect enhanced ozone deposition to dry soil [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
14. Cationic disulfide-functionalized worm gels.
- Author
-
Ratcliffe, L. P. D., Bentley, K. J., Wehr, R., Warren, N. J., Saunders, B. R., and Armes, S. P.
- Published
- 2017
- Full Text
- View/download PDF
15. Does vapor pressure deficit drive the seasonality of δ13C of the net land-atmosphere CO2 exchange across the United States?
- Author
-
Raczka, B., Biraud, S. C., Ehleringer, J. R., Lai, C.-T., Miller, J. B., Pataki, D. E., Saleska, S. R., Torn, M. S., Vaughn, B. H., Wehr, R., and Bowling, D. R.
- Abstract
The seasonal pattern of the carbon isotope content (δ
13 C) of atmospheric CO2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the δ13 C of the net land-atmosphere CO2 flux ( δsource ) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of δsource at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal δsource for each site after removing background influence and, when possible, removing δ13 C variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March-September) variation in δsource at the forest sites (0.5‰ variation). We did not find a consistent seasonal relationship between VPD and δsource across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in δsource . In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in δsource (5‰) dominated by seasonal transitions in C3 /C4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined δsource . Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in δ13 C of land-atmosphere CO2 exchange ( δsource ) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of δsource were at grassland and urban sites, driven by changes in C3 /C4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate δsource when background atmospheric observations are remote and/or prone to anthropogenic influence. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
16. Development and field testing of a rapid and ultra-stable atmospheric carbon dioxide spectrometer.
- Author
-
Xiang, B., Nelson, D. D., McManus, J. B., Zahniser, M. S., Wehr, R., and Wofsy, S. C.
- Subjects
SPECTROMETER design & construction ,ATMOSPHERIC carbon dioxide & the environment ,GAS cylinders - Abstract
We present field test results for a new spectroscopic instrument to measure atmospheric carbon dioxide (CO
2 ) with high precision (0.02 ppm at 1 Hz) and demonstrate high stability (within 0.1 ppm over more than 8 months), without the need for hourly, daily, or even monthly calibration against high-pressure gas cylinders. The technical novelty of this instrument (ABsolute Carbon dioxide, ABC) is the spectral null method using an internal quartz reference cell with known CO2 column density. Compared to a previously described prototype, the field instrument has better stability and benefits from more precise thermal control of the optics and more accurate pressure measurements in the sample cell (at the mTorr level). The instrument has been deployed at a long-term ecological research site (the Harvard Forest, USA), where it has measured for eight months without on-site calibration and with minimal maintenance, showing drift bounds of less than 0.1 ppm. Field measurements agree well with those of another commercially available cavity ring-down CO2 instrument (Picarro G2301) run with a standard calibration protocol. This field test demonstrates that ABC is capable of performing high-accuracy, unattended, continuous field measurements with minimal use of calibration cylinders. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
17. Long-term eddy covariance measurements of the isotopic composition of the ecosystem–atmosphere exchange of CO2 in a temperate forest.
- Author
-
Wehr, R., Munger, J.W., Nelson, D.D., McManus, J.B., Zahniser, M.S., Wofsy, S.C., and Saleska, S.R.
- Subjects
- *
EDDY flux , *MASS spectrometry , *PHOTOSYNTHESIS , *CARBON dioxide , *LASER spectroscopy , *SOIL respiration - Abstract
Highlights: [•] We directly measure the isotopic composition of NEE in a forest by eddy covariance. [•] Precision is limited both by instrument noise and by horizontal heterogeneity. [•] Precision is sufficient to partition NEE into photosynthesis and respiration. [•] The ‘EC/flask’ indirect flux measurement method can be biased by 2‰. [•] Laser spectrometer accuracy is on par with isotope ratio mass spectrometry. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
18. The impact theory of spectral line shapes: a paradigm shift1.
- Author
-
May, A.D., Liu, W.-K., McCourt, F.R.W., Ciuryło, R., Sanchez-Fortún Stoker, J., Shapiro, D., and Wehr, R.
- Subjects
SPECTRAL lines ,STATISTICAL mechanics ,NONLINEAR optics ,SCATTERING (Physics) ,WIGNER distribution ,DENSITY matrices - Abstract
Copyright of Canadian Journal of Physics is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2013
- Full Text
- View/download PDF
19. Optical feedback cavity-enhanced absorption spectroscopy for in situ measurements of the ratio 13C:12C in CO2.
- Author
-
Wehr, R., Kassi, S., Romanini, D., and Gianfrani, L.
- Subjects
- *
SPECTRUM analysis instruments , *INFRARED spectroscopy , *GAS detector calibration , *SPECTROMETERS , *DIAGNOSTIC use of spectrum analysis - Abstract
We report on the design and laboratory performance of a portable infrared absorption spectrometer for the measurement of the isotopic ratio 13C:12C in CO2. The design relies on optical feedback cavity-enhanced absorption spectroscopy in the 2 μm spectral region to achieve optimal performance at ambient CO2 concentrations. The prototype instrument measures δ13C, relative to a standard calibration bottle, with a precision of ±0.7‰ for a 20-s integration time and with an automatic recalibration every 6 min. The absolute accuracy obtained is 0.9‰. The principal performance limitations are discussed along with improvements currently being implemented for the second generation instrument. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
20. Optical feedback cavity-enhanced absorption spectroscopy for in situ measurements of the ratio 13C:12C in CO2.
- Author
-
Wehr, R., Kassi, S., Romanini, D., and Gianfrani, L.
- Subjects
SPECTRUM analysis instruments ,INFRARED spectroscopy ,GAS detector calibration ,SPECTROMETERS ,DIAGNOSTIC use of spectrum analysis - Abstract
We report on the design and laboratory performance of a portable infrared absorption spectrometer for the measurement of the isotopic ratio
13 C:12 C in CO2 . The design relies on optical feedback cavity-enhanced absorption spectroscopy in the 2 μm spectral region to achieve optimal performance at ambient CO2 concentrations. The prototype instrument measures δ13 C, relative to a standard calibration bottle, with a precision of ±0.7‰ for a 20-s integration time and with an automatic recalibration every 6 min. The absolute accuracy obtained is 0.9‰. The principal performance limitations are discussed along with improvements currently being implemented for the second generation instrument. [ABSTRACT FROM AUTHOR]- Published
- 2008
- Full Text
- View/download PDF
21. The effectiveness of topical and oral tetracycline for acne.
- Author
-
SMITH, J. GRAHAM, CHALKER, DAN K., WEHR, RICHARD F., Augusta, Smith, J G Jr, Chalker, D K, and Wehr, R F
- Published
- 1976
22. Broadening, shifting, and line mixing in the 0310 <f>←</f> 0110 parallel Q branch of N2O
- Author
-
Vitcu, A., Ciurylo, R., Wehr, R., Drummond, J.R., and May, A.D.
- Subjects
- *
SPECTRUM analysis , *INFRARED spectroscopy , *ABSORPTION spectra , *EXCITON theory - Abstract
The 0310
← 0110 parallel Q branch of N2O has been studied at 297 K and over the pressure range 1–130 torr. Absorption spectra were recorded using a high resolution (1.5 MHz or 5 × 10-5 cm-1) and high signal-to-noise (> 3500:1) mid-infrared spectrometer based on difference-frequency infrared generation in AgGaS2. In the low-pressure range (1–11 torr) we obtained accurate values for the line strengths, the broadening coefficients, the weak mixing coefficients, and the overall shifting of the branch. The medium pressure results, ranging from 23 to 130 torr, were analyzed by treating the band as a whole, using a relaxation matrix formalism, based on an energy gap scaling law. We find, effectively, that only 36% of the rotationally inelastic collisions are associated with Q branch mixing, the rest presumably being associated withQ–P andQ–R mixing in the same vibrational band. The pressure shifting coefficient of the 0310← 0110 Q branch as a whole was also determined and found to be 5.8 × 10-3 cm-1/atm towards lower frequencies. [Copyright &y& Elsevier]- Published
- 2004
- Full Text
- View/download PDF
23. The pharmacokinetics and metabolism of lumiracoxib in chimeric humanized and murinized FRG mice.
- Author
-
Dickie, A.P., Wilson, C.E., Schreiter, K., Wehr, R., Wilson, E.M., Bial, J., Scheer, N., Wilson, I.D., and Riley, R.J.
- Subjects
- *
CARBOXYLIC acids , *PHARMACOKINETICS , *CELL metabolism , *GLUCURONIDES , *LABORATORY mice - Abstract
The pharmacokinetics and metabolism of lumiracoxib were studied, after administration of single 10 mg/kg oral doses to chimeric liver-humanized and murinized FRG mice. In the chimeric humanized mice, lumiracoxib reached peak observed concentrations in the blood of 1.10 ± 0.08 μg/mL at 0.25–0.5 h post-dose with an AUC inf of 1.74 ± 0.52 μg h/mL and an effective half-life for the drug of 1.42 ± 0.72 h (n = 3). In the case of the murinized animals peak observed concentrations in the blood were determined as 1.15 ± 0.08 μg/mL at 0.25 h post-dose with an AUC inf of 1.94 ± 0.22 μg h/mL and an effective half-life of 1.28 ± 0.02 h (n = 3). Analysis of blood indicated only the presence of unchanged lumiracoxib. Metabolic profiling of urine, bile and faecal extracts revealed a complex pattern of metabolites for both humanized and murinized animals with, in addition to unchanged parent drug, a variety of hydroxylated and conjugated metabolites detected. The profiles obtained in humanized mice were different compared to murinized animals with e.g., a higher proportion of the dose detected in the form of acyl glucuronide metabolites and much reduced amounts of taurine conjugates. Comparison of the metabolic profiles obtained from the present study with previously published data from C57bl/6J mice and humans, revealed a greater though not complete match between chimeric humanized mice and humans, such that the liver-humanized FRG model may represent a useful approach to assessing the biotransformation of such compounds in humans. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
24. The impact theory of spectral line shapes: a paradigm shift1.
- Author
-
May, A.D., Liu, W.-K., McCourt, F.R.W., Ciuryło, R., Sanchez-Fortún Stoker, J., Shapiro, D., and Wehr, R.
- Subjects
- *
SPECTRAL lines , *STATISTICAL mechanics , *NONLINEAR optics , *SCATTERING (Physics) , *WIGNER distribution , *DENSITY matrices - Abstract
An overview of the binary collision impact theory of spectral line shapes has been given to provide a unified statistical mechanical approach to line-shape theory, laser theory, nonlinear optics, and transport phenomena in dilute gases. The computation of spectral line profiles corresponding to those obtained from ultra-high-resolution spectral line-shape measurements requires numerical ab initio calculation of scattering amplitudes directly from the underlying dynamics of collisions between radiatively active molecules and their perturbers. The Wigner distribution function-density matrix is utilized to describe the kinetic theory of spectral line shapes and to discuss the various collisional processes that contribute to the kernel of kinetic equations. The influence of features of the potential energy surface on spectral parameters is also discussed, and the importance of comparing experimental line profiles directly with numerically computed line shapes obtained from reliable interaction potentials is emphasized. This contrasts sharply with the universal practice of comparing experimental line widths and shifts using some average or approximate theoretical scattering cross-sections and it contrasts sharply with fitting experimental profiles to some convenient analytical line-shape model; hence the phrase 'a paradigm shift' in the title of this work. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.