Nuclear quadrupole couplings in solid bromides and iodides

From measurements of pure nuclear quadrupole transitions at 77°K the following coupling constants (in Mc/sec) and asymmetry parameters have been obtained: for I127|eQq| =1765.846, ε2=0.00078 in CH3I; |eQq| =1897.368, ε2 = 0.00736 in CH 2I2; |eQq| = 2046.634, ε2=0.00033 in CHI3·3S8; |eQq| = 2130.33 for CI4; |eQq| =2069.17 for CF3I; |eQq| = 1324.788 and 1333.313, ε2=0.000082 and ≤0.000010 for the two nonequivalent I's in unit cell of SiI4; |eQq\ = 1484.339 and 1500.577, ε2 = 0.000087 and ≤0.000005 for the two nonequivalent I's in unit cell of GeI4; |eQq| = 1384.424 and 1394.190, ε2=0.000085 and ≤0.000016 for the two nonequivalent I's in unit cell of SnI4; |eQq| =1517.07, ε2=0.00008 in AsI3·3S 8; |eQq| = 1226.35, ε2 = 0.00101 in SbI 3·3S8. The coupling values of Br are: |eQq(Br 79)| = 437.27 and 441.15; |eQq(Br81)| = 365.272 and 368.514 for the two nonequivalent Br's in unit cell of PBr3 (T=87±4°K) ; |eQq(Br79)| = 329.000 and 345.920; |eQq(Br81)| = 274.856 and 288.980 for the two nonequivalent Br's in unit cell of SbBr3. From these coupling values the number of unbalanced p electrons in the atoms was calculated. The latter quantity was found to be closely related to chemical bond properties such as ionic character, and was found to vary systematically with chemical constitution. A cross bonding mechanism involving d orbitals is proposed to account for the iodine coupling in certain solids.

Duke Scholars

Author Hugh Robinson Physics