Beat Meyer

Absorption Spectrum of Na and K in Rare‐Gas Matrices

The absorption spectrum of Na and K in Ar, Kr, and Xe matrices in the region from 2000 to 8000 A has been studied as a function of temperature and, at 4°K, as a function of concentration. Observations on some spectra of Na in Ne are also included. The first member of the principal series, 2P32,12∘←2S12, can be observed in all matrices. Higher members are weak and can, in most matrices, not be assigned. At alkali concentrations≥0.5%, strong additional absorptions are observed which seem to be due to alkali—alkali interaction.Most transitions appear blue shifted and have triplet structure. The spectra are sharp in xenon but become increasingly diffuse in lighter rare‐gas hosts. The line shape indicates fine structure in most absorption features. During the warm‐up, the 2P←2S absorption broadens and shifts to the red. For a given ratio of observation temperature to melting point of host lattice, atomic absorption of the alkali metals seems to have the same linewidth in all of the observed matrices.

The visible spectrum of S3 and S4

Abstract A vibrational analysis of the long-known, but unanalyzed and inconclusively assigned absorption around 400 nm in sulfur vapor at 450°C and 20 Torr, with pure isotopes 34 S and 32 S yields T 0,0 = 23,465 cm −1 . All 34 vibrational band heads fit the progression of ν ′ = 420 cm −1 and ν ″ = 590 cm −1 . At high dispersion, doublet band heads with unresolved rotational structure can be recognized. Another long-known absorption system around 530 nm reveals neither vibrational nor rotational structure. Photolysis experiments with a 10 −3 M solution of chlorosulfanes in an isopentane-methylcyclohexane glass at 77°K and in a krypton matrix at 20°K show that S 3 Cl 2 yields a new species characterized by a progression of bands with ν ′ = 400 cm −1 , and T 0,0 = 23,400 ± 100 cm −1 in the glass, while photolysis of S 4 Cl 2 at 77°K yields a species with continuum absorption at 530 nm. Annealing experiments with S 2 in a krypton matrix at 20°K also yield the 530 nm absorption. The correlation of the photolysis reactions and spectra indicates that the 400 nm system is due to S 3 while the 530 nm is due to S 4 . We discovered that the characteristic absorption of S 3 and S 4 is also found in hot liquid sulfur, in trapped liquid sulfur, and in trapped sulfur vapor.

Spectra of porphyrins: XI. Absorption and fluorescence spectra of matrix isolated phthalocyanines

Abstract Absorption and fluorescence spectra of free base and zine phthalocyanines (H 2 Pc and ZnPc) were studied in matrices of Ar, Kr, Xe, CH 4 , N 2 , and SF 6 at liquid hydrogen temperature. ZnPc was also studied in CO. The spectra show considerable fine structure whose resolution decreases along the series Ar > CH 4 ≳ Kr ≳ Xe > N 2 ≳ SF 6 > CO. Only part of the fine structure seen in absorption appears in emission. Provisionally we view the spectrum as made up of a broad band arising from phonon exchange with the lattice and nophonon lines arising from distinct sets of molecules. However, the lack of apparent correspondence between the line structure of the two Q bands of H 2 Pc remains unexplained.

Phosphorescent Decay Time of Matrix‐Isolated GeO, GeS, SnO, and SnS, and the Lifetime of the Cameron Bands of CO‐Type Diatomics

The lifetime for the Cameron bands, a 3Π → X 1Σ, of GeO, GeS, SnO, and SnS has been measured in argon, krypton, and xenon at 20 and 33°K, and in SF6 at 20, 33, and 77°K. The values range from 100 μsec to 3 msec, depending on molecule, matrix, and temperature. The external heavy atom effect on lifetime is strongest for light solutes. The internal heavy atom effect, expressed as the ratio of lifetimes, is in excellent agreement with predictions by first‐order perturbation theory. Therefore, we used this theory to estimate the lifetime of the Cameron bands of CO, CS, SiO, and SiS in argon. The matrix observations are then used to deduce values for the lower limit of the corresponding gas‐phase lifetimes. It is demonstrated that, for forbidden transitions, lifetimes of matrix‐isolated molecules are a useful tool to estimate unknown gas‐phase values.

The ultraviolet spectra of matrix isolated disulfur monoxide and sulfur dioxide

Abstract The absorption spectrum of disulfur monoxide was observed in matrices at 20°K. All 18 observed bands of the (0, 0, ν3) - (0, 0, 0) progression fit the equation G(ν 3 ′) = 29 070 + 426 (ν 3 ′ + 1 2 ) − 4.80 (ν 3 ′ + 1 2 ) 2 + 0.075 (ν 3 ′ + 1 2 ) 3 . The matrix data was used to reassign the reported gas-phase data and to deduce ν2′ and ν2″. The absorption spectrum of sulfur dioxide in a krypton matrix at 20°K is tentatively assigned to a progression A(ν1, ν2, 0) ← X(0, 0, 0). The SO2 a-X phosphorescence, excited by absorption of light in either the C or A system, is strongly enhanced in the matrix. T00, ν1 and ν2 shifts are listed for solid argon, krypton, xenon, nitrogen, methane, SF6, and C4F8. The phosphorescence intensity is strongly temperature dependent. The temperature-intensity curves are consistent with an energy transfer model involving interaction of the SO2 triplet state with the lattice vibration.

Absorption and Phosphorescence Spectrum of Matrix‐Isolated Ferrocene

The absorption and fluorescence spectrum of ferrocene was studied in argon, krypton, xenon, nitrogen, and methane matrices at 20°K. Five electronic transitions were found in the region from 50 000–16 000 cm−1. The absorption bands appear sharper and the band structure simpler than in the vapor phase or solution. A weak but distinct phosphorescence spectrum was recorded, the lifetime of which varied between 1 and 4 sec in different matrices.

The spectrum of matrix isolated SeO2: Evidence for slow internal conversion between excited states

The spectrum of matrix-isolated SeO2 was studied between 2200 and 6000 A at 20°K. A strong absorption with a Franck-Condon maximum near 2750 A and an origin near 31 000 cm−1 is assigned to the S3 ← S0 transition. It coincides with the B ← X system of the gas phase. Weak and broad absorption bands in the 3000–4500 A region belong to S1 ← S0 and possibly also to T1 ← S0, corresponding to the gas-phase system C ← X. A strong yellow emission, which has a lifetime of < 0.2 msec in xenon, 2.5 msec in SF6 and 2.0 msec in C4F8, and which consists of a well resolved progression of vibrational bands, is assigned to the transition T1 → S0, corresponding to a 3B1 → X 1A1 of SO2. This yellow phosphorescence is excited in the S1 ← S0 region at 3100–3700 A. Excitation below 3200 A and with X-rays stimulates a broad blue fluorescence between 3000–4200 A which we assign to the transition S3 → S0. The unusually slow internal conversion, S3 → S1 can be attributed to strong perturbation of S1 by T1.

Charge‐Transfer Spectra of Iodine with Hydrogen Sulfide and Benzene in Low‐Temperature Matrices

The absorption spectrum of benzene–iodine and hydrogen sulfide–iodine was studied at 20°K in argon, krypton, xenon, methane, nitrogen, and sulfur hexafluoride in the spectral range of 2300 to 4500 A. In addition to the component spectra, strong bands were observed around 2800 A in all solvents. They are assigned to the electronic charge‐transfer transitions of the electron donor‐acceptor systems benzene–iodine and hydrogen sulfide–iodine, respectively. The bands are broad and exhibit coarse as well as fine structure. The latter corresponds closely to the ground‐state vibrational frequency of iodine. While the solvent shifts in the benzene–iodine system follow the predictions for the heavy‐atom effect, the shifts of the hydrogen sulfide–iodine bands appear reversed. The half‐width of the bands increases, for benzene–iodine, with increasing polarizability, but decreases for the hydrogen sulfide–iodine system. The absorbance of the charge‐transfer bands of the hydrogen sulfide system are stronger than those ...

The spectrum of matrix-isolated GeO and GeS

Abstract The spectrum of GeO and GeS was studied in the 14 000 to 50 000 cm −1 region in argon, krypton, xenon, oxygen, sulfur hexafluoride, and methane at 20°K. In both molecules the system A 1 Π -X 1 Σ is observed. The analysis of the spectrum of GeS corresponds to that in the gas phase. For GeO in xenon, vibrational bands to the red of the gas phase (0,0) are found. This suggests that the gas phase numbering should be corrected by +1. This yields a new T 0.0 = 36 996 cm −1 . In both molecules, excitation into the A state yields phosphorescence in the visible. The emission is assigned to the previously unknown transition a 3 Π- X 1 Σ, which corresponds to the Cameron bands of isovalent CO. T 0.0 of the a 3 Π state in SF 6 at 20°K is 26 945 ± 200 cm −1 for GeO, and 22 465 ± 200 for GeS. From the transition energies in various matrices we deduce a gas phase value of T 0.0 = 26 900 ± 200 cm −1 for GeO and 22 500 ± 200 cm −1 for GeS. The phosphorescence results from matrix-induced intersystem crossing. Absorption and emission shifts are consistent with the external heavy atom effect. The spectrum of matrix-isolated GeO and GeS is in all respects analogous to that of SnO and SnS.

Fluorescence and Induced Phosphorescence of Formaldehyde in Solid Low‐Temperature Solutions

The absorption and emission spectrum of formaldehyde was studied in xenon, krypton, and sulfur hexafluoride and without matrix between 20° and 200°K in the region of 2600–6000 A. Matrix isolation of formaldehyde, even at M/R 1000, is dependent on solvent. The SF6 yields more than 99% isolation, xenon 90%, and krypton only 50%. The S1←S0 absorption is broad in all cases, and the system T1←S0 is too weak to be studied in detail. Strong emission in the 3800–5400‐A region is observed. The emission spectrum is independent of the exciting frequency between 2500 and 3500 A. In pure formaldehyde it is due to fluorescence of S1→S0 only, and in matrices it is due to simultaneous and overlapping fluorescence and phosphorescence. The fluorescence resembles the gas‐phase spectrum and is analyzed accordingly. Phosphorescence is caused by intersystem crossing. The phosphorescence yield increases with solvent polarizability and decreases reversibly with increasing temperature until diffusion occurs. Phosphorescence yield...