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Intensity analysis of overlapped discrete and continuous absorption by spectral simulation: The electronic transition moment for the BX system in I2
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Image of FIG. 1.
FIG. 1.

Several determinations of the electronic transition strength as a function of R for the BX transition in I2. The legend gives reference numbers for previous works (Refs. 5 and 16–20). Most error bars are ±1σ, as is also the size of the point from Ref. 20. The exception is the present determination (solid lines), where ±2σ is used for clarity of display.

Image of FIG. 2.
FIG. 2.

I2 absorption spectra recorded for two instrumental slit widths using a Shimadzu UV2101 Spectrophotometer. The two spectra are not quantitatively comparable, as the I2 pressure was only approximately constant over the time taken to record these. The true continuum absorbance (A c ), as estimated from the results of the study, is near its weakest in this spectral region.

Image of FIG. 3.
FIG. 3.

R-centroid as a function of wavelength, for bands having υ″ = 0 − 3 and υ′ = 0 − 55. The open points come from bands having FCFs in the range 0.004–0.045; the filled points have smaller FCFs. The open points are well represented by .

Image of FIG. 4.
FIG. 4.

Hyperfine structures of several even-J″ lines in the I2 BX system, from Refs. 5 (bottom two) and 24. The pattern of evenly spaced groups of components, with an extra gap between the first two groups, holds also for odd J″.

Image of FIG. 5.
FIG. 5.

Profiles of even-J″ (four overlapped traces) and odd-J″ lines (two) near 532 nm, from Ref. 24, with uniform component strength assumed. The P13 line of the 43-0 band (dotted) has smaller component spread and varying strengths (Ref. 23). The illustrated Doppler width is for the lines at 532 nm. All profiles were generated from components arrayed as in Fig. 4, with zero being the lowest frequency.

Image of FIG. 6.
FIG. 6.

Spectral segment with strong absorption from low υ″ levels. Band heads are identified at bottom, LS residuals top. Baseline average was 0.00371(5). This fit yielded a standard deviation of 6.1 × 10−4, which is comparable to the average for the two baseline spectra (6.9 × 10−4).

Image of FIG. 7.
FIG. 7.

Spectral segment with strongest absorption from excited υ″ levels. Numbers at bottom identify υ levels of bands involving υ″ = 3 (long), 4 (medium), and 5 (short lines). Baseline average 0.00325(5). Standard deviation of fit = 7.4 × 10−4, as compared with 8.2 × 10−4 for the baseline spectra.

Image of FIG. 8.
FIG. 8.

Transition strength as a function of wavelength, as obtained from 38 spectra recorded on 2 days. Error bars represent 1σ. Weighted fits of the two data sets to a linear function of λ yield nearly identical results (overlapped straight lines).

Image of FIG. 9.
FIG. 9.

Current estimates of total continuum absorptivity (points, identified as in Fig. 8), compared with the estimated total from Ref. 16. Also shown are the CX and AX contributions, as estimated in Ref. 16 (solid lines) and in Ref. 17 (dashed).

Image of FIG. 10.
FIG. 10.

Revised estimate of |μ e |2 from least-squares fit of 18 A T values from Ref. 37 together with 37 |μ e |2 values from Table II. Error bars are 1σ. Included for comparison are the Ref. 10 results and theoretical estimates from Ref. 36.

Image of FIG. 11.
FIG. 11.

A T values from Ref. 37 compared with results computed for recommended transition moment function. The two open points at small υ were omitted from the final least-squares fit, along with one |μ e |2 value from Table II at 590 nm.


Generic image for table
Table I.

Representation of absorption line profiles as sums of six Doppler components.a,b

Generic image for table
Table II.

Results from analyzed I2 BX spectra.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Intensity analysis of overlapped discrete and continuous absorption by spectral simulation: The electronic transition moment for the B–X system in I2