Department of Chemistry,and the Enrico Fermi Institute

THE UNIVERSITY OF

CHICAGOChicago, IL 60637, USA

An Interactive Loomis-Wood Package For

Spectral Assignment In Igor Pro, Version 2.0

Christopher F. Neese

What is a Loomis-Wood Plot?

• A fitting function, νfit(m), is chosen to model a series in the spectrum. ν fit(m) = ν 0 + (2B”eff + ΔBeff ) m + ΔBeff m2 + … m = -J” (P-branch) or J”+1 (R-branch)

• Each line in the spectrum is assigned a value of m based on the closest predicted line.

• The residuals, ν obs - ν fit(m), of the fit are plotted versus m.

• The Loomis-Wood plot would just be a residual plot, except that every observed line is plotted, whether it is in the series or not.

Na2 (1,0) band

• F. W. Loomis and R. W. Wood, Phys. Rev. 32, 223-236 (1928).

• Fit based on Q branch.

• P and R branches clearly visible as smooth curves.

History

• Difficult to use in initial assignment process before the advent of computer.

• 1960s: First computer program to generate Loomis-Wood plots. J. F. Scott and K. N. Rao J. Mol. Spectrosc. 20, 461-

463 (1966)

• 1980s: Interactive Loomis-Wood assignment programs. B. P. Winnewisser, J. Reinstädtler, K. M. T. Yamada ,

and J. Behrend, J. Mol. Spectrosc. 136, 12-16 (1989).

Version 2.0

• The add-in is Macintosh and Windows compatible.  (Version 1.0 was not Macintosh compatible.)

• There is a detailed manual and a tutorial to help users get started.• The add-in provides an organized line/assignment database.• Lines can be assigned to multiple series.• The add-in gracefully handles band heads. • Multiple Loomis-Wood data sets can be created within a single Igor

experiment.• Multiple plots of a single Loomis-Wood data set can be created

within a single Igor experiment.• There is a user-extensible extract assignments feature.  This feature

allows the add-in to be used easily with external fitting programs.• Since the add-in is written for Igor (instead of as a stand-alone

program) all of Igor’s features are available to the add-in.  For example, printing and graphics export are provided by Igor, not the add-in.

HCNH+ Loomis-Wood

More details TA02

HCNH+ Loomis-Wood

HCNH+ Loomis-Wood

HCNH+ Loomis-Wood

C2H4 Loomis-Wood

N2+ Loomis-Wood

Acknowledgements

• Oka Group Current Members:

• Oka• Jennifer Gottfried• Chris Morong• Aaron Schoeffler

Former Members:• Dan Hullah• Mike Lindsay• Ben McCall• Chris Tarsitano

• Norman Craig

http://fermi.uchicago.edu/freeware/