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A. Overview The graphical user interface (GUI) computer program, jb95.exe, accepts experimental data in an ASCII format consisting of frequency and intensity pairs. Cubic spline interpolation routines are used to linearize the ASCII data in frequency. After input conversion, three separate binary files are created, each representing a different level of horizontal scale expansion. The compression factor and the method of determining the intensity per unit frequency interval is selected by the user for each level of scale expansion. The top level of view is usually chosen to have a horizontal compression factor so that the entire file will be displayed over a single screen. In this case, the maximum intensity over each frequency interval is typically used since, otherwise, digital averaging would wash out most spectral features. The most expanded level of view provides access to the linearized raw data at full experimental resolution. An intermediate level is also available for reviewing larger spectral regions and for precise positioning during scale expansion of very large data files. Various sections of the spectrum are accessed via toolbar buttons that expand and contract the data about the cursor position by rapidly switching between these different levels. Once these files are created, the speed to access any spectral region is nearly instantaneous and independent of the original data record length. Up to nine independent channels may be simultaneously displayed and additional tool bar buttons are provided for scaling and offsetting the data in each channel. All of relevant files are kept in a separate folder including a special working directory file used to record the filenames, display factors and calibration information for that folder. Theoretical rotational spectra are generated by an independently-executed console-based rotor program, iar95.exe. A dialog in jb95.exe provides an interface to the rotor program for convenient access to the input parameters. Rotational constants, Watson's centrifugal distortion parameters, and Coriolis and quadratic angular momentum cross terms are easily added or modified to calculate rotational spectra for one-state (microwave) and two-state (vibrational and electronic) systems. Based on these parameters, the rotor program generates a simulated set of transitions (a line set). Each transition is assigned an electric dipole selection rule label (band type label), six asymmetric rotor quantum numbers, and a calculated frequency and intensity for each line. The theoretical stick spectrum is imported into one of nine simulation channels that can be graphically overlaid and compared with the experimental data. The independent channels are useful for the deconvolution of overlapping spectra. Each simulated line may be convoluted with a Lorentzian, Gaussian, or Voigt lineshape function to adequately match the experimental data. Two fitting strategies are implemented for the refinement of the model parameters: i) spectral pattern matching through step-wise parameter adjustment and ii) linear least-squares regression after quantum-number assignment of experimental frequencies. For the first method, the simulated spectrum is regenerated upon step-wise changes in the model parameters. Each new transition frequency is calculated from the sum over the products of the modified parameters and the Feymann energy derivatives calculated from the eigenvectors of the Hamiltonian. The method is accurate for small changes in the parameters and when the derivatives are slowly varying functions of the parameters. The line intensities are not altered by this procedure and therefore, are not exact. The primary advantage of using this method is that it allows for the rapid regeneration of the theoretical line set, which permits the user to visually evaluate its parameter dependence for pattern matching purposes. Additional dialog boxes are used as a convenient interface for making step-wise changes in the parameter values. Mouse-controlled track bars provide for smooth variation of individual rotational constants or for changes in the parameter pairs, B+C and B-C. The magnitude of the parameter change per unit track bar step is user adjustable. An additional control in the dialog is provided for regeneration of the exact frequencies, intensities and derivatives using the rotor program, when the validity of the approximation may be suspect. When nuclear quadrupole interactions are important, separate control and track bar dialogs are available for quantum-number listings that include experimental assignments and for variation of the coupling constants. The second computer-assisted method for the systematic refinement of the rotorparameters is by means of a linear least-squares fitting procedure. The process begins with the creation of an assignment file that contains a list of experimental frequencies and the associated quantum-number labels. A dialog control is used to retrieve the quantum labels from simulated lines that are bracketed by an adjustable window positioned using the cursor. Additional dialog controls are used for selecting a specific line in the list and for assigning and deleting the associated experimental frequency also defined by the cursor position. Calculated lines that are selected reveal the experimental frequency with a vertical line on the display. When saved to file, the collection of assigned lines are used by the rotor program to minimize the observed-minus- calculated (O-C) standard deviation using a least squares procedure based on a singular-value-decomposition algorithm. A dialog control updates an auxiliary parameter set with the best-fit parameters, standard uncertainties, and O-C standard deviation of the assigned line set. Through examination of these values and from comparisons with the original parameters, the quality of the fit may be evaluated prior to updating and displaying the new simulated spectrum. If the changes are acceptable, the process is repeated until all experimental lines are assigned. Once a spectrum is fit, an additional option to create a binary file from the convoluted stick spectrum frees the simulation resource for further analysis of other overlapping subspectra. A separate dialog and console-based program, quad95.exe, is available for least- squares refinement of nuclear quadrupole coupling constants for a single nucleus up to second-order in each rotational state. As a visual aid for the determination and refinement of rotational band types defined by the different Ka and Kc selection rules, an additional dialog is provided for control over the magnitudes of each band type (a-, b- or c-type) by means of three vertical track bars. The simulated intensities of any given band type are rescaled and graphically updated upon adjustment of the track bar position. This procedure is particularly useful if the orientation of the transition dipole moment is unknown. The percentage contribution of each band type to the total band strength is also displayed for accurate determination of the orientation angles.
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