Liubomir Misev

Charge transfer half‐collisions: Photodissociation of the Kr⋅O+2 cluster ion with resolution of the O2 product vibrational states

The photodissociation of the Kr⋅O+2 cluster ion has been studied in the visible and UV regions of the spectrum (350–580 nm) using a crossed high energy ion beam/laser beam experiment. Photodissociation of Kr⋅O+2 occurs by a charge transfer transition to Kr+⋅O2 state(s). The only ionic product observed was Kr+. A value for the dissociation energy of the Kr⋅O+2 cluster of D00(Kr–O+2) ∼0.33 eV was estimated from the results. A compilation of ion–molecule cluster dissociation energies is given. The product angular distributions indicate that the lifetime of the excited state(s) is less than a rotational period. In the visible region of the spectrum the products are Kr+(2P3/2)+O2(2Σ−). For the UV it is argued that one of the products is probably electronically excited [i.e., either Kr+(2P1/2) or O2(1Δg)]. The product relative kinetic energy distributions show resolved features that can be assigned to production of the product O2 in specific vibrational states. Information on the product rotational excitation w...

High‐resolution gas phase emission and laser induced fluorescence excitation spectra of 1,3,5‐C6F3H3+ and 1,3,5‐C6F3D3+: Critical bands in the Jahn–Teller effect analysis

Cooled gas phase laser induced fluorescence excitation (LIFEX) spectra of 1,3,5‐C6F3H3+ (h3+) and 1,3,5‐C6F3D3+ (d3+) ions were obtained between 4600 and 4110 A at a resolution of 1 cm−1. Band intensities were corrected for laser power variations. Gas phase discharge emission spectra of the same ions were photographed at a resolution of 0.25 cm−1 from 4450 to 4800 A and at 0.1 cm−1, between 4500 and 4700 A. In emission, only the spectral region λ<4580 A, corresponding to the 000 band and bands to lower wavelengths, is reported here. Particular regions of the LIFEX spectra were also recorded at a resolution of 0.25 cm−1. Vibronic analysis of the B 2A″2–X 2E″ transition is made on the basis of five (seven) e′, three a′1, and one a″2 excited state fundamental frequencies which were assigned in the h3+ (d3+) ions. A few low‐lying ground state levels, among which the first j=3/2 (A1, A2) levels of mode 6 (e′), the most active Jahn–Teller (JT) mode, are particularly critical. Some discrepancies in band relati...

Laser induced excitation spectra of the cations of 1,3-pentadiynes, R(CC)2H+; R CH3, CD3: (A2E ← X2E) and of 2,4-hexadiynes, R (CC)2R+; R CH3, CD3; (A2Eu ← X2Eg) in the gaseous phase

Abstract Laser induced excitation spectra, A (π −1 ) ← X (π −1 ), of methyl, and trideuteromethyl, substituted diacetylene cations are reported. The well resolved vibrational structure is assigned to yield the frequencies of several of the totally symmetric fundamentals for the excited electronic state. These complement the values obtained for the ground cationic states from the corresponding emission spectra. The excitation spectra show that for these cations the radiative decay is apparent up to ≈0.4 eV internal energy in the A state in spite of the fact that fragment ions are also detected.

Lifetimes of C-2 in rotational levels of the B̃2Σ+u state in the gas phase

Abstract Lifetimes of C - 2 in rotational levels of the B 2 Σ + u :ν′ = 0, ν′ = 1 states have been measured. C - 2 was produced from bromoacetylene and rare-gas metastables and the B 2 Σ + u —X 2 Σ + g transition was laser excited. The lifetimes are constant within a vibrational level, 77 = 8 ns for ν′= 0 and 73 = 7 ns for ν′ = 1. The oscillator strength f νo = 0.044 ± 0.004.

Emission and laser excitation spectra of rotationally cooled cations: Ã 2Πu↔X̃ 2Πg band systems of X(C≡C)2 X+, X=Cl, Br

The A 2ΠΩ,u↔X 2ΠΩ,g, Ω=3/2, 1/2, electronic transitions of rotationally and vibrationally cooled dichlorodiacetylene and dibromodiacetylene cations in the gas phase have been studied by emission and laser excitation spectroscopies. The emission spectra were obtained by electron impact excitation of the molecules seeded in a supersonic helium free jet and the excitation spectra by laser‐excited fluorescence of cations cooled to liquid nitrogen temperature. The narrowing of the vibronic bands in the spectra allow the vibrational frequencies for these cations in the X 2ΠΩ,g and A 2ΠΩ,u states to be inferred to within 1–2 cm−1. Complementary use of both sets of data enable the spin‐orbit components to be unambiguously identified and many spectral features to be interpreted. The vibrational frequency trends are also discussed.

Fragmentation dynamics and energy disposal in photodissociation of (N2O)2+ in the 458–660 nm wavelength range

Abstract The nitrous oxide dimer cation (N2O)2+ has been studied in the visible wavelength range by photodissociation of a mass-selected high-energy ion beam followed by energy analysis of the charged photofragments. Information on the angular anisotropy of the fragmentation process has been obtained by rotating the polarization direction of the laser light. The results allow conclusions to be drawn about the lifetime of the optically accessed excited electronic state and on the energy disposal in the photofragmentation event.

Emission and laser excitation spectra of rotationally cooled cations in the gas phase: Ã2Π ↔ X̃2Π band systems of 2X+, X Cl, Br

Abstract Emission and laser excitation spectra of the A 2 Π ω ↔ X 2 Π ω transition of rotationally and vibrationally cooled chloroand bromodiacetylene cations have been obtained. The emission was excited by electron impact of a seeded supersonic helium free jet and the fluorescence by laser excitation of cations cooled to liquid nitrogen temperature following Penning ionisation. Comparison of the two sets of spectra locates the spin—orbit, ω = 3 2 , 1 2 , components and enables the main spectral features to be identified. The vibrational frequencies of many of the fundamentals could be inferred to within 1–2 cm −1 for the cations in the X 2 Π and A 2 Π states.

Spectroscopic characterisation of open-shell cations. Laser excitation spectra of XCCX+ (X = Cl, Br)

Abstract Laser excitation spectra of the A2ΠΩ,g ⇌ X2ΠΩ,u, electronic transition of rotationally and vibrationally cooled dichloro- and dibromoacetylene cations in the gas phase have been recorded. Vibrational frequencies for these cations in their excited state have been inferred from the spectra. These and other spectroscopic data obtained are discussed.

Gas-Phase Structure Studies on Open-Shell Organic Cations by Means of their Radiative Decay

One of the traditional ways of obtaining data on the electronic and geometric structure of gaseous species is by emission spectroscopy (1). Historically, the study of the rotational details of the band systems in the emission spectra of many diatomic, and some triatomic, cations provided fundamental knowledge of their structures (2). These aspects are discussed and illustrated by Herzberg in a review article on the Spectra and Structure of Molecular Ions (3) as well as in further publications (4, 5).

Laser excitation spectra Ã2Π3/2â†X2Π3/2 of the bromoacetylene and deuterobromoacetylene cations in the gas phase

Laser excitation spectra of the A2Π3/2â†�X2Π3/2 electronic transition of rotationally cooled bromo- and deuterobromo-acetylene cations in the gas phase have been obtained. The cations were produced by Penning ionisation in a liquid-nitrogen-cooled environment. The vibronic band systems have been analysed and the vibrational frequencies of the fundamentals for these cations in their A2Π3/2 states inferred.