Ab initio calculations on the ground and low-lying electronic states of the Cl3 radical: emission from Cl3

Photolysis of Matrix-Isolated HCl−Cl2 Complexes: Electronic Absorption and Emission Spectra Provisionally Assigned to Cl3

“…Kawasaki et al obtained a gas phase laser excitation spectrum in the range 415−427 nm that was tentatively assigned to Cl 3 . Following this work, Wright et al suggested that a 370−420 nm emission band, observed when Cl 2 was photodissociated under relatively high-pressure conditions, might also originate from Cl 3 . In parallel with the experimental efforts there have been many attempts to calculate potential energy surfaces for trihalogens using ab-initio ,− and semiempirical methods. ,− …”

“…The mechanism would then be that initial excitation populates an excited vibronic level that reemits mostly at short wavelengths. (Ab-initio calculations predict a substantial increase in the bond angle on electronic excitation. ,, ) Vibrational relaxation populates levels that emit to longer wavelengths, owing to the changes in the Franck−Condon factors (e.g., transitions to excited bending vibrational levels of the ground state become more favorable). Hence, the decay of the long wavelength emission would be artificially slowed by the collisional modification of the fluorescence spectrum.…”

“…I 2 F and ClIF resulting from F 2 + I 2 and F 2 + ICl reactions, and Br 3 from the photolysis of (Br 2 ) 2 dimers, were detected by mass spectrometry. With the possible exception of Cl 3 , , trihalogens have not yet been characterized in the gas phase by IR or optical spectroscopy. Several trihalogens that contained fluorine atoms have been stabilized in rare gas matrices and characterized by IR absorption and Raman techniques. − (Note that spectra originally attributed to matrix-isolated Cl 3 and Br 3 were later reassigned to the respective negative ions …”

“…The proposed technique for matrix isolation of trihalogens is a simple modification of the approach used in the time-resolved reaction studies. ,, HX−YZ complexes are trapped in solid Ar and then photolyzed. The hydrogen atom readily escapes the matrix cage, − while the halogen atoms remain trapped. − To test this method, we have examined Cl 3 as the search for the spectrum could be guided by theoretical calculations 15,26-32 and the gas phase results. , …”