An experimental comparison of rotational temperature and gas kinetic temperature in a discharge

1996 ◽  
Vol 29 (5) ◽  
pp. 1197-1201 ◽  
Author(s):  
A N Goyette ◽  
W B Jameson ◽  
L W Anderson ◽  
J E Lawler
Keyword(s):  
Rotational Temperature ◽  
Experimental Comparison ◽  
Kinetic Temperature

ROTATIONAL AND VIBRATIONAL INTENSITY DISTRIBUTION OF THE FIRST NEGATIVE BANDS IN SUNLIT AURORAL RAYS

1960 ◽  
Vol 38 (3) ◽  
pp. 458-476 ◽  
Author(s):  
A. Vallance Jones ◽  
D. M. Hunten
Keyword(s):  
Solar Radiation ◽  
Intensity Distribution ◽  
Thermal Equilibrium ◽  
Degrees Of Freedom ◽  
Rotational Temperature ◽  
Dissociative Recombination ◽  
Rotational Line ◽  
Kinetic Temperature ◽  
Excitation Process ◽  
Line Intensities

Spectra of sunlit auroral rays were obtained from Saskatoon during the auroras of September 3/4 and 4/5, 1958. The resolution of these spectra was sufficiently high to enable measurements to be made of the relative intensities of the lines of the 0–0 first negative [Formula: see text] band as well as the relative intensities of bands of the Δυ = −1 sequence of this system. An analysis of the rotational line intensities shows they are consistent with an excitation process in which [Formula: see text] ions in thermal equilibrium with the atmosphere at 2200 °K fluoresce under the influence of solar radiation. The vibrational intensity distribution also is consistent with a fluorescent excitation from a state of thermal equilibrium at about 2050 °K. It is shown that the results are not consistent with a fluorescent excitation process in which the rotational and vibrational degrees of freedom of the [Formula: see text] ions come into radiative equilibrium with the solar radiation. Earlier conclusions that radiative equilibrium did hold for vibration are shown to be in error as a result of the high rotational temperature and the low dispersion used. It is concluded that the destruction of [Formula: see text] ions as a result of dissociative recombination proceeds sufficiently fast to prevent any significant approach to radiative equilibrium. This investigation provides a strong indication that the kinetic temperature of a sunlit auroral ray (perhaps in the 400–500 km region) is in the neighborhood of 2000 °K. This may be somewhat higher than the temperature of the normal atmosphere at this height.

scholarly journals Detection of New Ammonia Sources

1980 ◽  
Vol 87 ◽  
pp. 83-84
Author(s):  
G.H. Macdonald ◽  
A.T. Brown ◽  
L.T. Little ◽  
D.N. Matheson ◽  
M. Felli
Keyword(s):  
Hyperfine Structure ◽  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Column Density ◽  
Rotational Temperature ◽  
Kinetic Temperature ◽  
Excitation Temperature ◽  
Hydrogen Density

Ammonia is a favoured molecule for the study of molecular clouds since several important parameters of the cloud can be deduced from simple observations of the J,K=1,1 and 2,2 inversion doublet transitions and the hyperfine structure in the (1,1) line. With the additional knowledge of the kinetic temperature Tk from observations of CO, for example, it is possible to compute the excitation temperature of the (1,1) line (T11), the rotational temperature between the (1,1) and (2,2) levels (T21), the molecular hydrogen density n(H2) and ammonia column density N(NH3) (see, for example, Martin and Barrett, 1978).

scholarly journals Technical Note: Bimodality in Mesospheric OH Rotational Population Distributions and Implications for Temperature Measurements

2018 ◽  
Author(s):  
Konstantinos S. Kalogerakis
Keyword(s):  
Rotational Temperature ◽  
Systematic Errors ◽  
Technical Note ◽  
Rotational Relaxation ◽  
Kinetic Temperature ◽  
Vibrational Quantum Number ◽  
Mesopause Region ◽  
Quantum Numbers ◽  
Population Distributions ◽  
Inherent Feature

Abstract. Emission from the OH Meinel bands is routinely used to determine rotational temperatures that are considered proxies for the kinetic temperature near the mesopause region. Previous observations determined OH rotational temperatures that show a dependence on the vibrational level, with the temperature rising overall as the OH vibrational quantum number v increases. The source of this trend is not well understood and has generally been attributed to deviations from thermodynamic equilibrium. This Technical Note demonstrates that the existence of bimodal OH rotational population distributions is an inherent feature of rotational relaxation in gases and can provide an explanation for the previously reported temperature trend. The use of only a few lines from rotational transitions involving low rotational quantum numbers to determine rotational temperatures does not account for the bimodality of the OH rotational population distributions and leads to systematic errors overestimating the OH rotational temperature. This Note presents selected examples, discusses the relevant implications, and considers strategies that could lead to more reliable OH rotational temperature determination.

OH spectroscopy and chemistry investigated with astronomical sky spectra

2007 ◽  
Vol 85 (2) ◽  
pp. 77-99 ◽  
Author(s):  
P C Cosby ◽  
T G Slanger
Keyword(s):  
Population Distribution ◽  
Rotational Temperature ◽  
Critical Evaluation ◽  
Wavelength Region ◽  
High Spectral Resolution ◽  
Emission Region ◽  
Kinetic Temperature ◽  
Data Set ◽  
Population Distributions ◽  
Population Ratio

This study summarizes the use of a large catalog of astronomical sky spectra to study different aspects of OH spectroscopy and chemistry in the terrestrial night sky. The sky spectra are unique in that they have high spectral resolution, cover the entire visible wavelength region in one exposure, and are intensity-calibrated with respect to standard stars. The intensity calibration, in particular, allows a significant revision to the OH Meinel band intensity distribution that has been in use for 43~years and permits critical evaluation of the many available sets of OH emission coefficients. The spectra further allow the OH rovibrational population distributions to be monitored throughout many nights. The OH vibrational population distribution is found to change during the night, with the population ratio between the extreme high-v and low-v levels that we can detect, v = 9 and v = 3, varying by as much as a factor of two; the low-v levels being predominant earlier in the night. It has been common to determine the kinetic temperature of the OH emission region by assuming that it is equal to the low-J rotational temperature associated with particular OH bands, typically bands originating in the v = 6 and v = 8 levels. The present calibrated data set reveals that the rotational temperatures are significantly greater for high-v than for low-v levels, the typical difference between v = 3 and v = 8 being 15 K. Previous attempts to establish that a difference existed are consistent with our current observations, although conclusions from those earlier results were limited by relatively wide error limits. The present rovibrational population measurements, which extend to high rotational levels (J′ ≤ 25.5), also reveal that the high-J populations are largely independent of vibrational level — the high-J population in v = 3 is similar to that in v = 7.PACS Nos.: 92.60.H, 92.60.hw, 33.20.–t, 33.20.Kf, 33.70.–w

scholarly journals Technical note: Bimodality in mesospheric OH rotational population distributions and implications for temperature measurements

2019 ◽  
Vol 19 (4) ◽  
pp. 2629-2634 ◽  
Author(s):  
Konstantinos S. Kalogerakis
Keyword(s):  
Rotational Temperature ◽  
Systematic Errors ◽  
Technical Note ◽  
Rotational Relaxation ◽  
Kinetic Temperature ◽  
Vibrational Quantum Number ◽  
Mesopause Region ◽  
Quantum Numbers ◽  
Population Distributions ◽  
Inherent Feature

Abstract. Emissions from the OH Meinel bands are routinely used to determine rotational temperatures that are considered proxies for the kinetic temperature near the mesopause region. Previous observations determined OH rotational temperatures that show a dependence on the vibrational level, with the temperature rising overall as the OH vibrational quantum number v increases. The source of this trend is not well understood and has generally been attributed to deviations from thermodynamic equilibrium. This technical note demonstrates that the existence of bimodal OH rotational population distributions is an inherent feature of rotational relaxation in gases and can provide an explanation for the previously reported temperature trend. The use of only a few lines from rotational transitions involving low rotational quantum numbers to determine rotational temperatures does not account for the bimodality of the OH rotational population distributions and leads to systematic errors overestimating the OH rotational temperature. This note presents selected examples, discusses the relevant implications, and considers strategies that could lead to more reliable OH rotational temperature determination.

scholarly journals Measuring the Distribution and Excitation of Cometary CH3OH Using ALMA

2015 ◽  
Vol 11 (A29A) ◽  
pp. 233-236 ◽  
Author(s):  
M. A. Cordiner ◽  
S. B. Charnley ◽  
M. J. Mumma ◽  
D. Bockelée-Morvan ◽  
N. Biver ◽  
...  
Keyword(s):  
Rotational Temperature ◽  
Solar Irradiation ◽  
Line Of Sight ◽  
Kinetic Temperature ◽  
Spherically Symmetric ◽  
Temperature Profiles ◽  
Spatially Resolved ◽  
Adiabatic Cooling ◽  
Excitation Processes ◽  
Spectrally Resolved

AbstractThe Atacama Large Millimeter/submillimeter Array (ALMA) was used to obtain measurements of spatially and spectrally resolved CH3OH emission from comet C/2012 K1 (PanSTARRS) on 28-29 June 2014. Detection of 12-14 emission lines of CH3OH on each day permitted the derivation of spatially-resolved rotational temperature profiles (averaged along the line of sight), for the innermost 5000 km of the coma. On each day, the CH3OH distribution was centrally peaked and approximately consistent with spherically symmetric, uniform outflow. The azimuthally-averaged CH3OH rotational temperature (Trot) as a function of sky-projected nucleocentric distance (ρ), fell by about 40 K between ρ= 0 and 2500 km on 28 June, whereas on 29 June, Trot fell by about 50 K between ρ =0 km and 1500 km. A remarkable (~50 K) rise in Trot at ρ = 1500-2500 km on 29 June was not present on 28 June. The observed variations in CH3OH rotational temperature are interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling, and heating through Solar irradiation, but collisional and radiative non-LTE excitation processes also play a role.

scholarly journals Dense cores in the HH24–26 outflow region

1987 ◽  
Vol 122 ◽  
pp. 179-180
Author(s):  
K. M. Menten ◽  
C. M. Walmsley ◽  
R. Mauersberger
Keyword(s):  
Optical Depth ◽  
Hyperfine Splitting ◽  
Rotational Temperature ◽  
High Density ◽  
Kinetic Temperature ◽  
Dark Cloud ◽  
Dense Cores ◽  
Depth Ratio ◽  
Hh Objects ◽  
Outflow Region

We have made observations of the (1,1) and (2,2) inversion lines of ammonia (NH3) towards the dark cloud region containing the Herbig-Haro (HH) objects 24–27. These transitions are only excited at H2 densities >104 cm−3, and thus probe high density gas. From the observed hyperfine splitting one can calculate optical depths. The optical depth ratio can be used to determine the rotational temperature T21 which is equal to the kinetic temperature under dark cloud conditions.

scholarly journals Hyperfine group ratio: a recipe for deriving kinetic temperature from the ammonia inversion lines

2020 ◽  
Vol 499 (3) ◽  
pp. 4432-4444
Author(s):  
Shen Wang ◽  
Zhiyuan Ren ◽  
Di Li ◽  
Jens Kauffmann ◽  
Qizhou Zhang ◽  
...  
Keyword(s):  
Parameter Space ◽  
Rotational Temperature ◽  
Signal To Noise Ratio ◽  
Real Data ◽  
Computer Time ◽  
Kinetic Temperature ◽  
Line Profiles ◽  
Intensity Ratios ◽  
Internal Error ◽  
Uncertainty Level

ABSTRACT Although ammonia is a widely used interstellar thermometer, the estimation of its rotational and kinetic temperatures can be affected by the blended hyperfine components (HFCs). We have developed a new recipe, referred to as the hyperfine group ratio (HFGR), which utilizes only direct observables, namely the intensity ratios between the grouped HFCs. As tested on the model spectra, the empirical formulae in the HFGR can derive the rotational temperature (Trot) from the HFC group ratios in an unambiguous manner. We compared the HFGR with two other classical methods, intensity ratio and hyperfine fitting, based on both simulated spectra and real data. The HFGR has three major improvements. First, it does not require modelling the HFC or fitting the line profiles, so it is more robust against the effect of HFC blending. Second, the simulation-enabled empirical formulae are much faster than fitting the spectra over the parameter space, so both computer time and human time can be saved. Third, the statistical uncertainty of the temperature ΔTrot as a function of the signal-to-noise ratio (S/N) is a natural product of the HFGR recipe. The internal error of the HFGR is ΔTrot ≤ 0.5 K over a broad parameter space of rotational temperature (10–60 K), linewidth (0.3–4 km s−1) and optical depth (0–5). When there is spectral noise, the HFGR can also maintain a reasonable uncertainty level at ΔTrot ≤ 1.0 K when S/N > 4.

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