Synopsis We demonstrate the importance of ionization from Rydberg orbitals via experimental and theoretical work focusing on the strong-field dissociative single ionization of small hydrocarbons. Our ...findings suggest that Rydberg states should be routinely considered when studying polyatomic molecules in intense laser fields.
A coincidence 3-D momentum imaging technique is employed to study the dissociation of a metastable NO2+ beam in an intense ultrafast laser field. We find that dissociation into N+ + O+ is aligned ...perpendicular to the laser polarization for intensities below 1015 W/cm2 while higher intensities (~1016 W/cm2) yield a prominent contribution from molecules breaking parallel to the field. The latter feature may be due to direct 2-photon transition to the vibrational continuum of the X2Σ+ ground state, a surprising multiphoton vibrational excitation.
A unified low‐temperature reaction mechanism on the formation of acenes, phenacenes, and helicenes—polycyclic aromatic hydrocarbons (PAHs) that are distinct via the linear, zigzag, and ...ortho‐condensed arrangements of fused benzene rings—is revealed. This mechanism is mediated through a barrierless, vinylacetylene mediated gas‐phase chemistry utilizing tetracene, 4phenacene, and 4helicene as benchmarks contesting established ideas that molecular mass growth processes to PAHs transpire at elevated temperatures. This mechanism opens up an isomer‐selective route to aromatic structures involving submerged reaction barriers, resonantly stabilized free‐radical intermediates, and systematic ring annulation potentially yielding molecular wires along with racemic mixtures of helicenes in deep space. Connecting helicene templates to the Origins of Life ultimately changes our hypothesis on interstellar carbon chemistry.
Kalt abserviert: Polycyclische aromatische Kohlenwasserstoffe (PAKs) können durch molekulares Massenwachstum über Anellierungsreaktionen bei niedrigen Temperaturen gebildet werden. Der über barrierelose Vinylacetylen‐basierte Gasphasenchemie vermittelte Mechanismus hinterfragt die Annahme, dass molekulares Massenwachstum zu PAKs hohe Temperaturen benötigt.
The dissociation of CD+ induced by intense 30 fs pulses of central wavelengths 385 nm and 790 nm, over a range of peak intensities (5 × 1013 − 1 × 1016 W/cm2), was measured using a coincidence 3D ...momentum imaging technique. The observed kinetic energy release and angular distributions of the different products are presented and the possible dissociation pathways are discussed.
The dissociation of CD super(+) induced by intense 30 fs pulses of central wavelengths 385 nm and 790 nm, over a range of peak intensities (5 x 10 super(13) - 1 x 10 super(16) W/cm super(2)), was ...measured using a coincidence 3D momentum imaging technique. The observed kinetic energy release and angular distributions of the di erent products are presented and the possible dissociation pathways are discussed.
A coincidence 3-D momentum imaging technique is employed to study the dissociation of a metastable NO super(2+) beam in an intense ultrafast laser field. We find that dissociation into N super(+) + O ...super(+) is aligned perpendicular to the laser polarization for intensities below 10 super(15)W/cm super(2), while higher intensities (~10 super(16)W/cm super(2)) yield a prominent contribution from molecules breaking parallel to the field. The latter feature may be due to direct 2-photon transition to the vibrational continuum of the X super(2) capital sigma super(+) ground state, a surprising multiphoton vibrational excitation.
The effect of substituted phenothiazines was studied in three different systems; bacteria and cancer cells and reverse transcriptase enzyme of Moloney leukemia virus. F'lac and hemolysin plasmids ...were eliminated by some substituted phenothiazines from E. coli at a very low frequency. The same phenothiazine derivatives also were synergistic with tetracycline in bacteria and shown antimutagenic effect in Ames test. No mutagenic effects were observed in TA 98 strain of Salmonella typhimunium. Chloroethyl-substituted phenothiazines showed antimutagenicity equivalent to the parent compounds; however, phthalimido-substituted phenothiazines had higher antimutagenicity of 50%. P-glycoprotein responsible for multidrug resistance was also inhibited in tumor cells. The accumulation of the fluorescent rhodamine 123 in the phenothiazine treated multi-drug resistant tumor cells was measured by flow cytometry. Some of the substituted phenothiazines were effective P-glycoprotein blockers, while some compounds had moderate activity, but others were without effect as compared to 5 microM verapamil. On the basis of computer analysis there are some correlations between the biological activities and the dipole moments, and entropy of the studied molecules. Our results suggest that the inhibition of Hly+ plasmid replication and P-glycoprotein function may depend partly on similar electronic properties of the studied phenothiazine derivatives. The activity of Moloney leukemia virus reverse transcriptase was inhibited by the substituted phenothiazines, however, no basic differences were found in the activities of phthalimido- and chloroethyl substituted phenothiazines.
The dissociation of an H$_2^+$ molecular-ion beam by linearly polarized,
carrier-envelope-phase-tagged 5 fs pulses at 4$\times10^{14} $W/cm$^2$ with a
central wavelength of 730 nm was studied using a ...coincidence 3D momentum
imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission
direction of H$^+$ fragments relative to the laser polarization were observed.
These asymmetries are caused by interference of odd and even photon number
pathways, where net-zero photon and 1-photon interference predominantly
contributes at H$^+$+H kinetic energy releases of 0.2 -- 0.45 eV, and
net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These
measurements of the benchmark H$_2^+$ molecule offer the distinct advantage
that they can be quantitatively compared with \textit{ab initio} theory to
confirm our understanding of strong-field coherent control via the
carrier-envelope phase.
The dissociation of an H\(_2^+\) molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4\(\times10^{14} \)W/cm\(^2\) with a central wavelength of 730 nm was studied ...using a coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction of H\(^+\) fragments relative to the laser polarization were observed. These asymmetries are caused by interference of odd and even photon number pathways, where net-zero photon and 1-photon interference predominantly contributes at H\(^+\)+H kinetic energy releases of 0.2 -- 0.45 eV, and net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These measurements of the benchmark H\(_2^+\) molecule offer the distinct advantage that they can be quantitatively compared with \textit{ab initio} theory to confirm our understanding of strong-field coherent control via the carrier-envelope phase.
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