Hyperfine structure in a linear/symmetric rotor with a single quadrupolar nucleus

     This is a simple predictive program as found in the (now defunct) EXETER, UK rotational spectroscopy group of A.C.Legon. The changes made concern only commenting and output.

NSYM.FOR The listing
ARHCL35.DAT Specimen data set for the linear dimer Ar...H35Cl
ARHCL35.RES Results file for the data above

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Prediction of hyperfine structure in a rotor with a single quadrupolar nucleus

        This program calculates the nuclear quadrupole splitting structure for an asymmetric top with a single quadrupolar nucleus. The calculation is only first order but the program is tailored towards producing quick diagnostic plots for confrontation with spectra.

        ASQ1P calculates frequency shifts, relative intensities, as well as coefficients a and b of χaa and χbb in the expression:

        ν hyperfine = ν hyperfinefree + a χaa + b χbb

       These coefficients can then be used in an external least squares program to fit χaa and χbb from just the splittings, and/or to derive hyperfine free transition frequencies.

        The recommended extension for data is .ASQ

ASQ1P.FOR The listing
ASQ1P.EXE Windows executable
H2OHCLAR.ASQ Specimen data set for the trimer (H2O...HCl)...Ar.

Please note that, as implied by the primes, the quantum numbers of the upper level should come first. If the transition declared in this way is a P-type transition (J' < J'') then you will find that in the output the program will change the arrow direction and the order of the labels. The arrow direction will still be consistent with the implication in the input that E(J') > E(J''). When in doubt you can always check against Appendix I of the 3rd edition of Gordy&Cook.

H2OHCLAR.RES Results file for the data above

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Fitting of nuclear quadrupole coupling in a rotor with up to 2 quadrupolar nuclei

        The program has an excellent pedigree since its predecessor was written in Flygare's group (by W.G.Read). Q2FIT fits transitions assigned in the I,F coupling scheme of the two nuclear spins with rotation, the calculation is in full diagonalization and includes spin-rotation and spin-spin terms. We have actually switched to SPFIT for such problems, but Q2FIT is sometimes useful for comparisons.

        The main limitation is that on the fitted off-diagonal quadrupolar tensor components, since only either χab or χac can be fitted. There is also no factorisation.

        The recommended that extension for data files is .Q2S

Q2FIT.FOR The listing
Q2FIT.EXE Windows executable
VHCL.Q2S The data set for the H-bonded complex vinyl fluoride...HCl (only the Cl nucleus), for which a particularly strong quadrupole mediated perturbation has been fitted, J.Chem.Phys. 93,3054(1990)
VHCL.RES Results for the above
ARCLCN.Q2S The data set for the vdWaals complex Ar...ClCN (Cl and N nuclei) set up from results in J.Chem.Phys. 75,631(1981) and reproducing the constants therein
ARCLCN.RES Results for the above

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Diagonalization of the inertial quadrupole tensor (with errors)


Rotation of the nuclear quadrupole tensor

        QDIAG diagonalizes the inertial quadrupole tensor and the features are as follows:

  • calculation of principal tensor components and of their errors
  • calculation of direction cosines and of their errors
  • calculation of quadrupolar rotation angles and of their errors
  • constants fitted by SPFIT, i.e. (3/2)χaa, (χbb-χcc)/4 etc. can be used directly
  • input is always taken from the top of the file QDIAG.INP, so that the remainder of the file can be used for storage, such as previous matched versions of inputs and outputs 
  • there is no explicit output to disk so for hardcopy use a pipeline such as QDIAG>qdiag.out

        QDIAG should be run from a Command Prompt window (the old MS-DOS window) or the current PowerShell, in order to see the screen output.  The directory in which this window is open should contain the QDIAG.INP file. 

        QPRINC serves to predict the inertial tensor from guessed principal quadrupole components and the angular difference between the inertial and principal quadrupole tensors. As for QDIAG the data is taken automatically from the top of the file QPRINC.INP, and if you want hardcopy use the pipeline QPRINC>qprinc.out.

QDIAG.FOR The listing
QDIAG.EXE Windows executable
QDIAG.INP Several examples of literature tensors for QDIAG. Only the top declaration is read by the program.
QDIAG.OUT Results for the data set as above obtained with the pipeline command QDIAG>qdiag.out
QDIAGA.OUT Results for diagonal quadrupole components specified as (3/2)χaa and (χbb-χcc)/4 obtained by bringing one of the lower declarations in QDIAG.INP to the top.

QPRINC.FOR The listing
QPRINC.EXE Windows executable
QPRINC.INP Specimen data, rotation is only in the ab=xz plane
QPRINC.OUT Results for the above

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