M. Noort

High resolution spectra of zinc porphin and magnesium porphin in a n-octane matrix at 4.2 K. Effect of the addition of ethanol and other solvents

Addition of solvent with free electron pairs on oxygen or nitrogen (ethanol, D2O, diethyl ether and pyridine) to zinc porphin (ZnP) in n-octane crystals causes the appearance of new spectra in absorption, flourescence and phosphorescence, superimposed on the normal ligand-free ZnP spectrum which has its origin at 17,954 cm−1 (absorption and flourescence) and 14,671 cm−1 (phosphorescence). The origins of the new spectra are displaced by 300–900 cm−1 to lower energy as compared to the normal spectrum. With ethanol and D2O the line widths of the origins are the same as observed for the normal spectra (<3 cm−1, whereas with diethyl ether and pyridine much broader lines result. Magnesium porphin in n-octane shows complicated spectra with many origins in the region 17,300–17,500 cm−1. After addition of ethanol a single spectrum remains with its origin at 17,415 cm−1 (absorption and flourescence). Microwave transitions between the spin components of the lowest triplet state have been used to distinguish between the solvated and unsolvated ZnP molecules.

High resolution spectra of palladium, platinum and copper porphins in n-octane crystals

Abstract High resolution Q -band absorption and emission spectra of palladium porphin (PdP), PtP and CuP in slowly grown single crystals of n -octane at 4.2 K are reported. The life times determined from the 0—0 line widths in the absorption spectra are given. Also the emission spectrum of CuP at 77 K is reported. The observed T D — T Q distance of CuP amounts to 320 cm −1 . A variation in peak intensities depending on sample preparation has been found.

Stark effect on the S1 ← S0 transition of the two tautomeric forms of chlorin studied by photochemical hole-burning in n-hexane and n-octane single crystals at 1.2 K

Abstract Stark experiments are reported on the S1 ← S0 0-0 transitions of chlorin (7.8-dihydroporphin) and its photoisomer in different sites in n-hexane and n-octane single crystals by photochemicals hole-burning at 1.2 K. For chlorin Δμ = +0.23 D, with ΔμtμtS0). For the photoproduct we estimate μ(S1) = 2.2 D with a site-dependent angle between μ(S1) and μ(S0) of up to 24.

Jahn-Teller instability of the first excited singlet state of zinc porphin: a study by Zeeman spectroscopy in some n-alkane host crystals at 4·2 K

Experiments in a strong magnetic field (7·5 T) have been performed on the S 1 ←S 0 absorption spectrum of zinc porphin (ZnP) at 4·2 K in n-alkane hosts ranging from n-heptane to n-decane, in order to determine the orbital angular momentum Λ, the frequency v, and the distortion parameter α of the active mode of the Jahn-Teller unstable state S 1. Although the crystal-field splitting δ varies strongly for the sites considered (δ = 5–109 cm-1), nearly-constant values for the other three parameters are obtained: Λ = 3.9–4.2, α = 1·1–1·3, and v = 171–180 cm-1. The results prove the validity of the model previously proposed for the Jahn-Teller instability of a metalloporphyrin in a crystal field. A low-frequency mode of 17 cm-1 is observed in the S 1 and S 0 states of ZnP in n-heptane. In the Zeeman spectra it leads to a level anticrossing, and in fluorescence and absorption it shows up in hot bands.

Zeeman effect of the S1 ← S0 transition of the two tautomeric forms of chlorin: a study by photochemical hole burning in an n-hexane host

Abstract Zeeman experiments are reported on the S 1 ← S 0 O-O transitions of chlorin (7,8-dihydroporphin) and its photoisomer in an n -hexane crystal by photochemical hole burning at 4.2 K. The holes shift with a quadratic field dependence of -39.0 MHz/T 2 (chlorin) and −245.3 MHz/T 2 (photoisomer). For chlorin A = ¦ 1 ¦ L z ¦S 2 > ¦=4.5. Single-site absorption and fluo spectra are reported. PPP calculations were performed.

Zeeman effect in the Q-band absorption spectrum of palladiumporphin in an n-octane single crystal

Abstract The Zeeman effect in the high resolution spectrum of palladiumporphin in a single crystal of n-octane at 4.2 K is reported. The two zero-point vibronic components |x〉 and |y〉 of the state S1 are split by 30 cm−1. They show a large second order Zeeman effect from which one derives |〈x|Lz|y〉| ⩾ 4.4 |h. In the field the high energy component shows a broadening proportional to H2.

The lowest triplet state of K2Cr2O7. Optical spectra and optically detected electron spin resonance at 1.2 K

Abstract High-resolution emission and excitation spectra are reported for a K2Cr2O7 crystal at 1.2 K, and the effect of microwave saturation on thes

Zeeman experiments on free-base porphin by means of photochemical hole-burning

Abstract Zeeman shifts were measured in the S 1 ← S o 0-0 transition of free-base porphin in a single crystal of n -octane by means of photochemical hole-burning at 4.2 K. On the application of a field parallel to the out-of-plane axis (z), holes burnt in zero-field shift with a quadratic field-dependence of −60.6 MHz/T 2 . After allowing for a diamagnetic correction, a value of Λ = {| 1 }| L z {|S2 > }|= 5.6 is obtained for the matrix element of the orbital angular momentum operator L z between the two lowest excited singlet states.

Zeeman experiments on the 3Eu α 1A1g transition of platinum porphein in an n-alkane single crystal at 4.2

Abstract We report absorption spectra from the ground state to the photoexcited triplet state of platinum porphin (PtP) in single crystals of n -octane (C 8 ) and n -decane (C 10 ) at 4.2 K, with and without a magnetic field. For PtP in C 10 the same transition was studied in emission. From the experiments, values are derived of the spin-orbit coupling parameter Z, the crystal field splitting δ and the orbital angular momentum A for PtP in the two hosts: Z = 76 ± 2 cm −1 (C 8 , C 10 ), δ = 71 ± 1 cm −1 (C 8 ), 55 ± 1 cm −1 (C 10 ) and A = 1.6 ± 0.1 (C 8 , C 10 ). For the ratio of the in-plane and the z-polarized electric dipole transition moments we obtain ¦ Mx,y ¦/¦ Mz ¦=76± 0.3 (C 8 ).

Zeeman effect on the S1 ← S0 transition of the photoisomer of chlorin in different sites in n-hexane studied by photochemical hole-burning

Abstract A Zeeman study of the S 1 ← S 0 transition of the unstable photoisomer of chlorin (7,8-dihydroporphin) in three different sites in an n -hexane single crystal at 4.2 K is presented. Zeeman shifts, detected via photochemical hole-burning, have a quadratic field dependence which varies for each site. The S 2 -S 1 energy separation in the four sites is determined and Λ = •〈S 1 • L z •S 2 〉• = 3.9.