Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 11 of 11
Full-Text Articles in Chemistry
Mass-Analyzed Threshold Ionization Of Lanthanide Imide Lnnh (Ln = La And Ce) Radicals From N–H Bond Activation Of Ammonia, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang
Mass-Analyzed Threshold Ionization Of Lanthanide Imide Lnnh (Ln = La And Ce) Radicals From N–H Bond Activation Of Ammonia, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang
Chemistry Faculty Publications
Ln (Ln = La and Ce) atom reactions with ammonia are carried out in a pulsed laser vaporization supersonic molecular beam source. Lanthanide-containing species are observed with time-of-flight mass spectrometry, and LnNH molecules are characterized by mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and a scalar relativity correction, electron correlation, and spin-orbit coupling for the Ce species. The MATI spectrum of LaNH exhibits a single vibronic band system with a strong origin band and two weak vibronic progressions, whereas the spectrum of CeNH displays two band systems …
Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—H And C—C Bond Activation Of 1-Pentene And 2-Pentene, Wenjin Cao, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang
Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—H And C—C Bond Activation Of 1-Pentene And 2-Pentene, Wenjin Cao, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang
Chemistry Faculty Publications
La atom reactions with 1-pentene and 2-pentene are carried out in a laser-vaporization molecular beam source. The two reactions yield the same metal-hydrocarbon products from the dehydrogenation and carbon–carbon bond cleavage of the pentene molecules. The dehydrogenated species La(C5H8) is the major product, whereas the carbon–carbon bond cleaved species La(C2H2) and La(C3H4) are the minor ones. La(C10H18) is also observed and is presumably formed by La(C5H8) addition to a second pentene molecule. La(C5H8) and La(C2 …
Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By Association And Carbon-Carbon Bond Cleavage Of Isoprene, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang
Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By Association And Carbon-Carbon Bond Cleavage Of Isoprene, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang
Chemistry Faculty Publications
La atom reaction with isoprene is carried out in a laser-vaporization molecular beam source. The reaction yields an adduct as the major product and C—C cleaved and dehydrogenated species as the minor ones. La(C5H8), La(C2H2), and La(C3H4) are characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of all three species exhibit a strong origin band and several weak vibronic bands corresponding to La-ligand stretch and ligand-based bend excitations. La(C5H8) is a five-membered metallacycle, whereas La(C2H2 …
Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang
Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang
Chemistry Faculty Publications
La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C4H6) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C4H6) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each of these …
Detection And Characterization Of The Tin Dihydride (Snh2 And Snd2) Molecule In The Gas Phase, Tony C. Smith, Dennis J. Clouthier
Detection And Characterization Of The Tin Dihydride (Snh2 And Snd2) Molecule In The Gas Phase, Tony C. Smith, Dennis J. Clouthier
Chemistry Faculty Publications
The SnH2 and SnD2 molecules have been detected for the first time in the gas phase by laser-induced fluorescence (LIF) and emission spectroscopic techniques through the Ã1B1–X̃1A1 electronic transition. These reactive species were prepared in a pulsed electric discharge jet using (CH3)4Sn or SnH4/SnD4 precursors diluted in high pressure argon. Transitions to the electronic excited state of the jet-cooled molecules were probed with LIF, and the ground state energy levels were measured from single rovibronic level emission spectra. The LIF spectrum of SnD2 …
Note: Improved Line Strengths Of Rovibrational And Rotational Transitions Within The X3Σ⁻ Ground State Of Nh, James S.A. Brooke, Peter F. Bernath, Colin M. Western
Note: Improved Line Strengths Of Rovibrational And Rotational Transitions Within The X3Σ⁻ Ground State Of Nh, James S.A. Brooke, Peter F. Bernath, Colin M. Western
Chemistry & Biochemistry Faculty Publications
Recently, a line list including positions and transition strengths was published for the NH X3Σ− rovibrational and rotational transitions. The calculation of the transition strengths requires a conversion of transition matrix elements from Hund’s case (b) to (a). The method of this conversion has recently been improved during other work on the OH X2Π rovibrational transitions, by removing an approximation that was present previously. The adjusted method has been applied to the NH line list, resulting in more accurate transition strengths. An updated line list is presented that contains all possible transitions with v′ and …
Predicted Properties Of Microhollow Cathode Discharges In Xenon, J. P. Boeuf, L. C. Pitchford, K. H. Schoenbach
Predicted Properties Of Microhollow Cathode Discharges In Xenon, J. P. Boeuf, L. C. Pitchford, K. H. Schoenbach
Bioelectrics Publications
A fluid model has been developed and used to help clarify the physical mechanisms occurring in microhollow cathode discharges (MHCD). Calculated current-voltage (I-V) characteristics and gas temperatures in xenon at 100 Torr are presented. Consistent with previous experimental results in similar conditions, we find a voltage maximum in the I-V characteristic. We show that this structure reflects a transition between a low-current, abnormal discharge localized inside the cylindrical hollow cathode to a higher-current, normal glow discharge sustained by electron emission from the outer surface of the cathode. This transition, due to the geometry of …
Excimer Emission From Cathode Boundary Layer Discharges, Mohamed Moselhy, Karl H. Schoenbach
Excimer Emission From Cathode Boundary Layer Discharges, Mohamed Moselhy, Karl H. Schoenbach
Bioelectrics Publications
The excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm, was studied in xenon and argon in a pressure range from 75 to 760 Torr. The thickness of the “cathode boundary layer” plasma, in the 100 μm range, and a discharge sustaining voltage of approximately 200 V, indicates that the discharge is restricted to the cathode fall and the negative glow. The radiant excimer emittance at 172 nm increases with pressure and reaches a value of 4 W/cm2 for …
Comparison Between The Ultraviolet Emission From Pulsed Microhollow Cathode Discharges In Xenon And Argon, Isfried Petzenhauser, Leopold D. Biborosch, Uwe Ernst, Klaus Frank, Karl H. Schoenbach
Comparison Between The Ultraviolet Emission From Pulsed Microhollow Cathode Discharges In Xenon And Argon, Isfried Petzenhauser, Leopold D. Biborosch, Uwe Ernst, Klaus Frank, Karl H. Schoenbach
Bioelectrics Publications
We measured the dynamic I–V characteristics and vacuum ultraviolet (VUV) emission lines of the second continuum in xenon (170 nm) and argon (130.5 nm) from pulsed microhollow cathode discharges (MHCD). For pulse lengths between 1 and 100 μs the dynamic I–V characteristics are similar in both inert gases. Only the time variation of the VUV emission line at 170 nm for xenon can be related to the dimer excited states. In argon the energy transfer between the Ar*2 dimers and the oxygen impurity atoms is responsible for a qualitatively different time behavior of the resonance line at 130.5 nm. …
Xenon Excimer Emission From Pulsed Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz
Xenon Excimer Emission From Pulsed Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz
Bioelectrics Publications
By applying electrical pulses of 20 ns duration to xenon microplasmas, generated by direct current microhollow cathode discharges, we were able to increase the xenon excimer emission by more than an order of magnitude over direct current discharge excimer emission. For pulsed voltages in excess of 500 V, the optical power at 172 nm was found to increase exponentially with voltage. Largest values obtained were 2.75 W of vacuum-ultraviolet optical power emitted from a single microhollow cathode discharge in 400 Torr xenon with a 750 V pulse applied to a discharge. Highest radiative emittance was 15.2 W/cm2. The …
Picosecond Laser Pulse Irradiation Of Crystalline Silicon, K. L. Merkle, H. Baumgart, R.H. Uebbing, F. Phillipp
Picosecond Laser Pulse Irradiation Of Crystalline Silicon, K. L. Merkle, H. Baumgart, R.H. Uebbing, F. Phillipp
Electrical & Computer Engineering Faculty Publications
Morphology changes introduced by picosecond laser pulses at λ = 532 nm and 355 nm in (111) and (100) silicon samples are studied by means of optical and high-voltage electron microscopy. Depending on energy fluence, orientation and wavelength, amorphous or highly defective regions may be created. From an analysis of damage thresholds and damage depth distributions it is concluded that melting and energy confinement precedes the formation of the structural changes.