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Additions and Corrections
The Journal of Physical Chemistry, Vol. 94, No. 5, 1990
ADDITIONS AND CORRECTIONS 1988, Volume 92
L. Hanley, J. L. Whitten, and S. Anderson*: Collision-Induced Dissociation and ab Initio Studies of Boron Cluster Ions: Determination of Structures and Stabilities. Page 5808. In Table 11, the ground state of Bzf is incorrectly identified as 211u. Two states should have been listed for Bz+, the ground state %, and the excited state zIIu.By use of the Whiteside basis, 6-3 1G*, the calculated total energies and equilibrium bond lengths, R (at the CI level), for B2+ are as follows:
2% 2=,
SCF, au
CI, au
R, A
-48.7656 -48.8070
-48.9 173 -48.9293
1.8 2.2
The original entry in the table was erroneously reported at the SCF equilibrium distance for the 211ustate. At the CI level, the above data show the 211ustate to be 0.33 eV higher than the zZ, state. The calculated dissociation energy B,+(22,) = B(2P) + B+('S) is 1.47 eV, and the calculated ionization potential of Bz(%,) to give Bz+(,Z,) is 8.1 eV. Improvement of the basis and more extensive CI would be expected to increase both the dissociation energy of Bz+ and ionization potential of B,. The low appearance potential of B+ B observed in the experiment would appear to correlate better with dissociation from the *ITuexcited state of B2+ than from the ground state. Contributions from this excited state to lowering the experimental appearance potential for CID of B,+ are unlikely however. Radiative coupling to the ground state should be reasonably strong, and the experimental delay between ion formation and collisions is at least 20 ms. A more likely problem in the experiments is vibrational excitation. In our experimental arrangement, we attempt to cool the hot nascent cluster ions by >5000 collisions with helium buffer gas. For a light cluster ion like Bz+,where the vibrational frequency is significantly greater than the average collision energy, quenching may be inefficient. Compounding this is the fact that very little B,+ is produced in our source (Figure 2 of the original paper), and the CID measurements are quite difficult. For heavier cluster ions two effects help with quenching. First, the residence time in the cooling trap is longer, and coupled with larger size, this gives a much larger number of buffer gas collisions. In addition, the higher density of vibrational states in a large cluster makes deexcitation possible through a series of steps requiring only small V-T transfer. We would like to acknowledge P. Bruna and J. S. Wright's work on the ionization of B, bringing the omission of the 211gstate to our attention (preprint of work submitted for publication; J . Chem. Phys. 1989, 91. 1 126).
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