The dynamics of palladium phthalocyanine excited states in magnetic fields at low temperatures

• Published in: Chemical physics Vol. 102; no. 1; pp. 193 - 203
• Main Authors: Chen, Wen-Hsiung, Rieckhoff, Klaus E., Voigt, Eva-Maria
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.02.1986; Elsevier
• Subjects: Atomic and molecular physics; Exact sciences and technology; Molecular properties and interactions with photons; Optical activity and dichroism; magnetooptical and electrooptical spectra; Physics; Shpolskij effect; Temperature; Palladium Complexes; Very low temperature; Singlet state; Transition metal Complexes; Experimental study; JJ coupling; Inorganic compound; Triplet state; Lifetime; Zeeman effect; Metallophthalocyanine; LS coupling; Phosphorescence; Low temperature
• ISSN: 0301-0104
• DOI: 10.1016/0301-0104(86)85131-X

The spectral and transient behavior of both the first excited singlet and the lowest triplet state of randomly oriented palladium phthalocyanine (PdPc) molecules in a Shpol'skii matrix were investigated at liquid-helium temperatures with magnetic fields up to ≈ 63 kG. It is estimated that the expectation value of the orbital angular momentum in S 1 of a free molecule amounts to Λ ≳ 3.1 ℏ from which an orbital reduction factor q of ≈ 0.8 follow. The phosphorescence lifetimes (τ p) of the observed field-split spin components differ substantially. At T=4.2 K and a field strength of ≈ 63 kG, the central component has τ p = 11.0 ± 1.0 μs and the low-energy component has τ p = 29 ± 2 μs, respectively. It is also found that at high fields very fast spin-lattice relaxation occurs among the triplet spin levels of the ẑ ⊥ H molecules. The interesting field and temperature dependence of the rates were discussed. The spectral intensity behavior and the related dynamic aspects of the energy transfer of the complex at T ≈ 25 K and liquid-helium temperatures were accounted for as well, assuming an acceptable model for the relaxation mechanism.