Knowledge Bank

The previously accepted vibrational and rotational constants for the B state of iodine are unable to reproduce accurately either the observed absorption spectrum or the intensity distribution in $fluorescence.1$ We have remeasured portions of the B-X absorption system, using a 10-meter echelle-grating spectrograph at a resolving power of approx. 600,000. A new analysis of 719 line in the $6\prime \prime -3\prime ,7\prime \prime -41,4\prime \prime -51,5\prime \prime -71,1\prime \prime -111,2\prime \prime -21,2\prime \prime -131,0\prime \prime -251$, and $0\prime \prime -291$ bands, combined with previous measurements by $Mecke,2$ $Loomis,3$ and R. L. $Brown,4$ gives the following revised constants. [FIGURE]$\omega e\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=125.077cm-1Be\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=.028969cm-1\omega exe\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=.6830\alpha e\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=.0001561\omega eye\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=-.00633\gamma e\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=-4.03\times 10-7\omega eze\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=+.000039\delta e\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=-3.5\times 10-8De\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=4378.De\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\cong 3.5\times 10-9Te\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}=15784.\beta e\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\cong 3.9\times 10-10$ Combination differences for ground state levels will also be reported and compared with Rank's most recent $determinations.5$ Using these new constants, it was still found impossible to compute the correct Franck-Condon factors, using a numerical Rydberg-Klein-Rees method to obtain the potential, and a L\ddot{o}wdin iteration-variation procedure with numerical integration to solve the radial Schr\ddot{o}dinger $equation,6$ so long as the vibrational numbering originally $assigned2,3$ was retained. We found that decreasing the vibrational numbering of the B state by one unit brought the calculated intensity distribution and all observed fluorescence data into complete agreement.