Keyword NQR

This keyword activates the calculation of the nuclear quadrupole splitting as measured in NQR and NMR spectroscopy.
Options:
BARN / FM^2

	BARN		The values of the nuclear quadrupole moments are given in barns ($10^{-24}$ cm$^2$). This is the default.
	FM^2		The values of the nuclear quadrupole moments are given in fm$^2$.
	READ		Specifies that nuclear quadrupole moments and nuclear spins are read from the keyword body of NQR.

Description:
The basic outputs of the NQR keyword are the traceless electric field gradient (EFG) components at the positions of the nuclei and the corresponding anisotropy parameters $\eta$ defined as:

$$\eta = {{V_{xx} - V_{yy}} \over {V_{zz}}}%$$ (35)

with

$$\mid V_{zz} \mid > \mid V_{yy} \mid \geq \mid V_{xx} \mid%$$ (36)

If nuclear quadrupole moments for specific nuclei are supplied by the READ option of the NQR keyword, then the nuclear quadrupole coupling constants (in MHz) are calculated [258,259]. In the following input, the nuclear quadrupole moment of Cl is given by the assignment line (CL Q = -7.97) in the body of the NQR keyword. In this particular case, the nuclear quadrupole moment is given in fm$^2$.

 NQR READ fm^2
 CL Q = -7.97
 #
 GEOMETRY Z-MATRIX
 C1
 C2  C1  RCC
 Cl  C1  RCCl  C2  ACCCl
 H1  C1  RCH1  C2  ACCH1  Cl  180.0
 H2  C2  RCH2  C1  ACCH2  Cl  180.0
 H3  C2  RCH3  C1  ACCH3  Cl    0.0
 #
 VARIABLES
 RCC   1.332
 RCCl  1.726
 RCH1  1.079
 RCH2  1.078
 RCH3  1.090
 ACCCl 122.3
 ACCH1 123.8
 ACCH2 119.5
 ACCH3 121.0

The components of the nuclear quadrupole coupling constants for the Cl atom are printed in the output as:

 TRACELESS EFG COMPONENTS FOR ATOM 3 ( CL )

 XX COUPLING CONSTANT:  -29.794 MHz
 YY COUPLING CONSTANT:  -39.685 MHz
 ZZ COUPLING CONSTANT:   69.479 MHz
 EFG ANISOTROPY ETA  :    0.142

If the nuclear spin is also given in the input, as in the following example,

 NQR READ
 Cl Q = -0.0797 S = 1.5

then the energy levels of the nuclear quadrupole splitting [11] are also calculated. To print the corresponding NQR spin Hamiltonian matrix, use PRINT NQR in the input. The additional output reads as follows:

 PRINCIPAL AXES OF EFG TENSOR

               1          2          3
     1      0.00000    0.52718    0.84976
     2      1.00000   -0.00002    0.00001
     3      0.00003    0.84976   -0.52718




 NQR SPIN HAMILTONIAN MATRIX

               1          2          3          4
     1     17.36967    0.00000    1.42758    0.00000
     2      0.00000  -17.36967    0.00000    1.42758
     3      1.42758    0.00000  -17.36967    0.00000
     4      0.00000    1.42758    0.00000   17.36967




 EIGENVECTORS OF NQR SPIN HAMILTONIAN

               1          2          3          4
     1      0.00000   -0.04099    0.99916    0.00000
     2      0.99916    0.00000    0.00000    0.04099
     3      0.00000    0.99916    0.04099    0.00000
     4     -0.04099    0.00000    0.00000    0.99916



 NQR ENERGY LEVELS

 ENERGY LEVEL  1 =   -0.1743E+02 MHz
 ENERGY LEVEL  2 =   -0.1743E+02 MHz
 ENERGY LEVEL  3 =    0.1743E+02 MHz
 ENERGY LEVEL  4 =    0.1743E+02 MHz