High-resolution observations of the infrared spectrum of neutral neon

Journal of Research of the National Institute of Standards and Technology, May-June, 2004 by Craig J. Sansonetti, Marion M. Blackwell, E.B. Saloman

In order to estimate the uncertainty of the intensities, we examined the ratio of the standard deviation to the average value for each of the approximately 600 lines for which more than one measurement was made. From this analysis we observed that the relative uncertainty of the intensities is about 10% independent of intensity for lines with intensity of 100 or greater, 15% for lines with intensities 10 to 100, and 25% for lines weaker than 10. The analysis of uncertainties is summarized in Table 2, where we present the percentage of lines for which the relative standard deviation lies within 1, 2, and 3 times the stated uncertainty for each decade in the intensity. Based on this distribution, the stated uncertainties represent approximately a 90% level of confidence. The statistics for the 10 000 to 100 000 intensity range reflect the fact that the few lines with intensities greater than 50 000, especially those that are self-reversed, are somewhat less reproducible than weaker lines.

4. Results

Results of this work are presented in Table 3. Virtually all lines previously reported in this spectral region have been observed. Only lines that could be reliably classified as transitions between Ne I levels are reported in the table. Impurity lines of Ar I, Xe I, O I, C I, and Hg I were identified and removed. Also removed were 23 weak lines that we were unable to identify. The strongest of these had intensity 57. All others were much weaker.

The intensities reported in the first column of Table 3 are on a scale linear in photon number as described above. Lines that were used as internal standards for calibration of the spectra are indicated by an S following the intensity. An asterisk in this position denotes a line that is multiply classified. In almost all cases multiply-classified lines are associated with the small intervals between pair-coupled levels in 5[p.sup.5]nf and 5[p.sup.5]ng configurations. These transitions are unresolvable in observation of the emission spectrum because their Doppler widths exceed the level separation. The many unresolved blends of transitions to 5[p.sup.5]nd levels in Ref. [4] have all been resolved in this work.

The observed wavelengths and their uncertainties are given in the second and third columns of Table 3. Wavelengths shorter than 20 000 [Angstrom] are reported in standard air; wavelengths longer than 20 000 [Angstrom] are vacuum values. The observed vacuum wave numbers were converted to standard air wavelengths by using the index of refraction of air as calculated from the three term formula of Peck and Reeder [16]. Uncertainties are reported at the one standard deviation level representing a 68% confidence interval. The wavelengths have been rounded so that the uncertainty in the least significant digit does not exceed 20. Corresponding values of the vacuum wave number and its uncertainty are given in columns four and five.

The classification for each line is given in the remaining columns of Table 3. The configuration, term, and J value for the lower level is given first followed by the same information for the upper level. All level designations are given in the [J.sub.1]l coupling notation. The line identifications were initially made based on the Ne I level values reported by Kaufman and Minnhagen [5] and by Chang et al. [6]. A few identifications were later revised based on calculated transition probabilities and re-optimized level values determined in our comprehensive compilation of Ne I wavelengths and energy levels [8]. The classifications in Table 3 are fully consistent with Ref. [8].