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Nuclear spin dependence of the reaction of with H2. II. Experimental measurements
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10.1063/1.3587246
/content/aip/journal/jcp/134/19/10.1063/1.3587246
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/19/10.1063/1.3587246

Figures

Image of FIG. 1.
FIG. 1.

Schematic drawing of the hollow cathode cell used in this study. Technical drawings are available in the supplementary material (Ref. 26).

Image of FIG. 2.
FIG. 2.

Current during the discharge pulse for the four main sets of conditions used in this study. The discharge is started at t ∼ 230 μs, and is cut off at t ∼ 430 μs. Details about the choice of conditions are discussed in Secs. ??? and ???. The negative current after the discharge pulse is an artifact of the current monitor setup, which sees the pulser box recharging.

Image of FIG. 3.
FIG. 3.

A sample scan of the R(1,0) transition of in a n-H2 plasma produced by a liquid-nitrogen-cooled hollow cathode. The plot has been slightly modified for clarity by eliminating artifacts at the beginning and end of the discharge pulse resulting from electrical pickup.

Image of FIG. 4.
FIG. 4.

Kinetic and rotational temperatures and p- fraction (p 3) inferred from measurements of the R(1,0), R(1,1) u , R(2,2) l , and R(2,1) u transitions of in a liquid-nitrogen-cooled hollow cathode plasma consisting of 50% p-H2. The discharge is started at t ∼ 220 μs and is cut off at t ∼ 410 μs.

Image of FIG. 5.
FIG. 5.

Boltzmann plot of the first eight transitions of formed in a p-H2 plasma. The data are taken at t = 300 μs, about 70 μs after the start of the discharge pulse. Because of systematic underpopulation, the population of the (2,2) level is not taken into account for the rotational temperature calculation of p-.

Image of FIG. 6.
FIG. 6.

R(1,0) inegrated intensity as a function of cell pressure in an uncooled n-H2 plasma. The plotted data are selected at t = 300 μs. No error bars are shown, as only one scan was performed at each pressure.

Image of FIG. 7.
FIG. 7.

Experimental measurements of p- fraction plotted against p-H2 fraction for an uncooled plasma at 560 and 1430 mTorr.

Image of FIG. 8.
FIG. 8.

Kinetic and rotational temperatures as a function of p-H2 fraction in an uncooled plasma. Also plotted is the rotational temperature derived from comparison of the (2,2) and (1,1) levels, as an illustration of the underpopulation of the (2,2) level. Top: 560 mTorr. Bottom: 1430 mTorr.

Image of FIG. 9.
FIG. 9.

R(1,0) inegrated intensity as a function of cell pressure in a liquid-nitrogen-cooled n-H2 plasma. The plotted data are selected at t = 300 μs.

Image of FIG. 10.
FIG. 10.

Experimental measurements of p- fraction plotted against p-H2 fraction for a liquid nitrogen cooled plasma at 270 and 430 mTorr.

Image of FIG. 11.
FIG. 11.

Inferred temperatures as a function of p-H2 fraction in a liquid nitrogen cooled plasma. Top: 270 mTorr. Bottom: 430 mTorr.

Image of FIG. 12.
FIG. 12.

High temperature model fits to experimental measurements in an uncooled plasma.

Image of FIG. 13.
FIG. 13.

Time dependence of inegrated intensities of all four observed transitions in n-H2 (p 2 = 0.25, left) and p-H2 (p 2 = 0.999, right) plasmas under the different temperature and pressure conditions explored in this work. The integrated intensities are averaged over three scans of each transition. Nonzero intensities outside of the pulse are the result of a blind Gaussian fit to a noise feature within a spectrum with no absorption, resulting in a spurious “inegrated intensity.”

Image of FIG. 14.
FIG. 14.

Comparison of the data from the liquid nitrogen cooled hollow cathode with calculations from the low temperature model (Eq. (6)). For all curves shown, T kin = 135 K and S id = 0.1.

Image of FIG. 15.
FIG. 15.

Comparison of the data from the liquid nitrogen cooled hollow cathode with calculations from the low temperature model (Eq. (6)). For all curves shown, T kin = 135 K and S id = 0.9.

Image of FIG. 16.
FIG. 16.

Summary of all experimental data and the best estimates for α for each temperature. Also shown for reference are high temperature model traces for α = {0, 0.5, ∞}.

Tables

Generic image for table
Table I.

The rotational levels used in this work and their target transitions. Energies are relative to the forbidden (J, K) = (0, 0) level. Energies and transition frequencies are taken from literature values (Ref. 22). Transition dipole moments are calculated from the Einstein A coefficients (Ref. 23).

Generic image for table
Table II.

Integrated intensities of transitions from the lowest four rotational levels of in uncooled plasmas of varying p 2, with inferred kinetic and rotational temperatures and p 3 values. Numbers in parentheses represent 1σ uncertanties in the final digit(s).

Generic image for table
Table III.

Integrated intensities of transitions from the lowest four rotational levels of in liquid-nitrogen cooled plasmas of varying p 2, with inferred kinetic and rotational temperatures and p 3 values. Numbers in parentheses represent 1σ uncertanties in the final digit(s).

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/content/aip/journal/jcp/134/19/10.1063/1.3587246
2011-05-19
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Nuclear spin dependence of the reaction of H3+ with H2. II. Experimental measurements
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/19/10.1063/1.3587246
10.1063/1.3587246
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