Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Iodine stands as the best known diatomic halogen molecule. It is now followed by iodine monochloride. One of the three lowest ion-pair states, namely D' ((OMEGA) = 2), is characterized by using the Optical-Optical-Double-Resonance, (UPARR)(UPARR), state-selective polarization-labelling technique. Data were cumulated for vibrational levels v = 0-2 and 15-28, including extensive coverage of two avoided crossings between D' and E states, at v = 0 and 1. The main spectroscopic constants for D' state of I ('35)Cl are T(,e) = 39061.830(80), (omega)(,e) = 173.63(35), (omega)(,e)x(,e) = 0.5572(27), 10('2)B(,e) = 5.4782(41), 10('4)(alpha)(,e) = 2.019(10)cm('-1) and 10r(,e) = 3.350nm. The Rydberg-Klein-Rees (RKR) potential is given for the D'(2) ion-pair state of I('35)Cl up to v = 28. The D' state is perturbed by the neighboring (beta) state, their electronic interaction term is evaluated at 1.860(77), 93% of the Van Vleck pure precession value. The three lowest ion-pair states in ICl, D', (beta) and E, have very similar electronic energy, vibrational energy and equilibrium bond distance as it can be expected.;By extending the technique to three steps (OOTR), (UPARR)(UPARR)(DARR), we characterized the first excited state A' ((OMEGA) = 2), above the ground state of ICl. Data from v = 2 to 28 were fitted to a Dunham expansion, and v = 23 to 38 were fitted to a near-dissociation expansion. The main spectroscopic constants for A'(2) state of I('35)Cl are T(,e) = 12682.05(27), (omega)(,e) = 224.57(15), (omega)(,e)x(,e) = 1.882(29), 10('2)B(,e) = 8.648(48), 10('4) (alpha)(,e) = 6.48(23), 10('8) D(,e) (TURNEQ) 5.27(20) cm('-1) and 10r(,e) = 2.665nm. The A'(2) state shows some similarity with the other (('3)(pi)) case (a) signature states, namely A(1) and B(0('+)), their vibrational energy and equilibrium bond distance being very close. No sign of perturbation have been observed in A' state even if data of partial coverage go up to (TURN)70 cm('-1) from the dissociation limit, 17557.57cm('-1), I(('2)P(,3/2)) + Cl (('2)P(,3/2)) to which converge ten electronic states. The Rydberg-Klein-Rees (RKR) potential curve is given for A'(2) state of I Cl up to v = 38.



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