11 Data for Conventional Table-CI Transition Moments

This Table-CI module will calculate both electrical and magnetic dipole moments as well as oscillator strengths and lifetimes of excited states. The module will look to calculate the moment between a specific state (typically the ground state) and a set of additional states (typically the excited states). It is assumed that the CI eigen-vectors have been generated and are available on the appropriate FORTRAN interfaces. While in most cases the ground and excited state CI-vectors will reside on the same interface, FTN036, the module will allow the use of differing data sets for these vectors, a situation most likely to occur when the ground and excited states are of different symmetry.

11.1 TM

The TM directive is used to request Transition Moment analysis, and comprises two data lines. The first line is read to the variables TEXT, TEXTF and TEXTB using format (3A).

• TEXT should be set to the character string TM.
• TEXTF is an optional parameter that may be used to control the quantity of printed output produced by the module. Valid settings include the strings,
  • NOPRINT, to suppress the major part of the output from the module;
  • IPRINT, to produce an intermediate level of output;
  • FPRINT, to produce output suitable for debugging purposes.
• TEXTB is an optional parameter that should be set to the string BYPASS if the user wishes to bypass TM processing. Such usage is typically associated with restarting Table-CI calculations.

The second data line of the TM directive is used to specify the location of the CI-vectors, and the number of excited state vectors involved in the subsequent analysis. The line is read to the variables IFTNX, ISECX, IFTNE, ISECE, NSTATE using format (5I);

• IFTNX defines the FORTRAN data set reference number of the interface holding the CI-vector of the first state. Normally this vector will reside on FTN036, with IFTNX=36.

• ISECX defines the position of this first vector on the interface defined by IFTNX. Typically, for the first state of a given symmetry, the vector will be located first on the data set i.e., ISECX=1.

• IFTNE defines the FORTRAN data set reference number of the interface holding the CI-vector(s) of the set of additional states. Assuming these states are of the same symmetry as the first, then we would expect all the states involved to lie on the same interface i.e., IFTNE will also be set to 36. If, however, the set of states is of different symmetry to the first, then their vectors will almost certainly reside on a different interface, which we will assume reside on FTN037 i.e., IFTNE should be set to 37.

• ISECE defines the position of the first of the excited state vectors on the interface defined by IFTNE. Typically, if all the states involved are of the same symmetry, residing on the same data set (IFTNX=IFTNE), then the first excited state vector will be located second on the data set i.e., ISECE=2. When the first and excited states are of different symmetry, then different data sets will be involved, and the first of the excited state vectors will be the first on IFTNE.

• NSTATE - defines the number of excited state vectors involved, and is usually equal to the number of transition moment calculations to be performed. Thus if we wished to calculate the transition moment between the two lowest states of H₂O, then NSTATE would equal 1, and the TM data would appear as follows:

            TM
            36 1 36 2 1