J. Huc

Dissociation cross sections of silane and disilane by electron impact

Abstract The total dissociation cross sections for silane and disilane are reported for electron energies above their ionization thresholds up to 110 eV. The measurements are derived from a kinetic analysis of silane and disilane dissociation in a constant-flow multipole dc plasma reactor. The methane dissociation cross section was also measured and found in agreement with published data. Maxima for silane and disilane, occurring around 60 eV, are respectively (1.2±3)×10 −15 cm 2 and (2.6±0.6)× 10 −15 cm 2 . Total ionization cross sections are also measured and above 50 eV the ratios of dissociative ionization to dissociation cross sections are 0.5±0.1 and 0.25±0.10 respectively for silane and disilane. The probability for silane elimination in the disilane fragmentation reaches a maximum of 0.8 at 19 eV and decreases down to 0.5 at 100 eV. Dissociation processes of silane and disilane are discussed in comparison with methane and ethane

Growth of hydrogenated amorphous silicon due to controlled ion bombardment from a pure silane plasma

The growth process, optical and structural properties of a‐Si:H films deposited from a silane multipole dc discharge are analyzed by real time and spectroscopic ellipsometry, and ir absorption spectroscopy. Films deposited mainly from neutral polymerized species are systematically compared to films deposited from monomeric ionic species at various ion incident energy up to 100‐eV. An increase of ion bombardment energy is shown to favor the formation of high density homogeneous and isotropic films.

Silane dissociation mechanisms and thin film formation in a low pressure multipole dc discharge

A silane plasma is generated by a hot cathode dc discharge in a partially confining multipolar magnetic structure yielding hydrogenated amorphous silicon thin films on the walls. The low‐pressure range (0.1–5 mTorr) allows the analysis of the elementary processes for SiH4 dissociation. At low silane partial pressure the deposition rate remains in the range of 1–10 A/sec, but the contribution of ions to deposition can reach up to 80% in contrast with standard glow discharges.

Is there structure in the f0 mass region

Evidence is presented for structure in the f0-mass region in the reaction π+n→pπ+π− at a pion momentum of 11.7 GeV/c. A detailed analysis indicates that it is most unlikely that the structure is a statistical effect.

Growth characterization of a‐Si:H films by in situ ellipsometry in a silane multipole plasma

Fast real time ellipsometry has been performed to follow the growth of a‐Si:H films deposited in a low pressure D. C. discharge of silane. First results show that the growth is incompatible with a simple homogeneous layer by layer mechanism and suggest the presence of microstructure.

A study of the reactions π+d → dπ+π−π+ and π+d → dπ+π−π+π0 at 11.7 GeV/c

SummaryThe two coherent reactions π+d → dπ+π+π− and π+d → → dπ+π+π+π0 are studied in the 2 m DBC at the incoming momentum of 11.7 GeV/c. The production cross-sections are measured:σ=(0.37±±0.06) mb andσ=(0.24±0.05) mb respectively. The two reactions are analysed in the different LPS configurations. The dσ/dt′ distribution for the two reactions displays the same exp[−At′] shape withA⋍37 (GeV/c)−2 in both cases, thus indicating that the differential cross-sections are dominated by the deuteron form factor. The coherent inclastic interaction contains the channel π+d → θ0π+d with a cross-sectionσ==(20±5) µb and a signal for the B+-meson of about 12 µb. The four-pion masses display structures below 2 GeV/c.RiassuntoNella camera a bolle 2 m DBC del CERN esposta ad un fascio di π+ di 11.7 GeV/c si sono studiate le due interazioni coerenti π+d → π+π+π−d e π+d → π+π+π−π0d. Le sezioni d’urto di produzione sono rispettivamenteσ=(0.37±0.06) mb eσ=(0.24±0.05) mb. Si analizzano diversi aspetti dei due canali esclusivi tra cui le diverse configurazioni longitudinali più frequenti. La sezione d’urto differenziale dσ/dt′ presenta la stessa forma exp [−At′] con un valoreA⋍37 (GeV/c)−2 per entrambe le reazioni. Ciò implica la dominanza del fattore di forma del deutone su entrambi i processi in esame. La reazione coerente inelastica contiene un contributoσ=(20±5) µb del canale π+d → θ0π+d nel quale il segnale del mesone B+ è di circa 12 µb. Le masse effettive di quattro pioni mostrano strutture tipiche e significative perM∼2 GeV.РеэюмеИсследуются две когерентных реакции π+d → dπ+π−π+ и π+d → dπ+π−π+π0 в 2 м дейтериевой пуэырьковой камере при импульсе падающих частиц 11.7 ГзВ/с. Иэмеренные поперечные сечения рождения соответственно составляютσ=(0.37±±0.06))μб иσ=(0.24±0.05)μб. Исследуемые две реакции аналиэируются в раэли-чных LРS конфигурациях. Распределение dσ/dt′ для двух реакций обнаруживают ту же форму ехр [−At′] сA=37 (ГзВ/с)−2 в обоих случаях. Этот реэультат укаэы-вает, что дифференциальные поперечные сечения доминируют эа счет форм-фактора дейтрона. Когерентное неупругое вэаимодействие содержит канал π+d → ω0π+d с поперечным сечениемσ=(20±5)μб и сигнал для меэона В+ с величиной около 12μб. Эффективные массы четырех пионов обнаруживают типичную структуру дляM≼2ГзВ.

A Study of the Reactions pi+ d --> d pi+ pi- pi+ and pi+ d --> d pi+ pi- pi+ pi0 at 11.7-GeV/c

SummaryThe two coherent reactions π+d → dπ+π+π− and π+d → → dπ+π+π+π0 are studied in the 2 m DBC at the incoming momentum of 11.7 GeV/c. The production cross-sections are measured:σ=(0.37±±0.06) mb andσ=(0.24±0.05) mb respectively. The two reactions are analysed in the different LPS configurations. The dσ/dt′ distribution for the two reactions displays the same exp[−At′] shape withA⋍37 (GeV/c)−2 in both cases, thus indicating that the differential cross-sections are dominated by the deuteron form factor. The coherent inclastic interaction contains the channel π+d → θ0π+d with a cross-sectionσ==(20±5) µb and a signal for the B+-meson of about 12 µb. The four-pion masses display structures below 2 GeV/c.RiassuntoNella camera a bolle 2 m DBC del CERN esposta ad un fascio di π+ di 11.7 GeV/c si sono studiate le due interazioni coerenti π+d → π+π+π−d e π+d → π+π+π−π0d. Le sezioni d’urto di produzione sono rispettivamenteσ=(0.37±0.06) mb eσ=(0.24±0.05) mb. Si analizzano diversi aspetti dei due canali esclusivi tra cui le diverse configurazioni longitudinali più frequenti. La sezione d’urto differenziale dσ/dt′ presenta la stessa forma exp [−At′] con un valoreA⋍37 (GeV/c)−2 per entrambe le reazioni. Ciò implica la dominanza del fattore di forma del deutone su entrambi i processi in esame. La reazione coerente inelastica contiene un contributoσ=(20±5) µb del canale π+d → θ0π+d nel quale il segnale del mesone B+ è di circa 12 µb. Le masse effettive di quattro pioni mostrano strutture tipiche e significative perM∼2 GeV.РеэюмеИсследуются две когерентных реакции π+d → dπ+π−π+ и π+d → dπ+π−π+π0 в 2 м дейтериевой пуэырьковой камере при импульсе падающих частиц 11.7 ГзВ/с. Иэмеренные поперечные сечения рождения соответственно составляютσ=(0.37±±0.06))μб иσ=(0.24±0.05)μб. Исследуемые две реакции аналиэируются в раэли-чных LРS конфигурациях. Распределение dσ/dt′ для двух реакций обнаруживают ту же форму ехр [−At′] сA=37 (ГзВ/с)−2 в обоих случаях. Этот реэультат укаэы-вает, что дифференциальные поперечные сечения доминируют эа счет форм-фактора дейтрона. Когерентное неупругое вэаимодействие содержит канал π+d → ω0π+d с поперечным сечениемσ=(20±5)μб и сигнал для меэона В+ с величиной около 12μб. Эффективные массы четырех пионов обнаруживают типичную структуру дляM≼2ГзВ.

A study of the reactions π+d → dπ+π−π+ and π+d → dπ+π−π+π0 at 11.7 GeV/c@@@Исследование реакций π+d → dπ+π−π+ и π+d → dπ+π−π+π0 при 11.7 ГзВ/с

SummaryThe two coherent reactions π+d → dπ+π+π− and π+d → → dπ+π+π+π0 are studied in the 2 m DBC at the incoming momentum of 11.7 GeV/c. The production cross-sections are measured:σ=(0.37±±0.06) mb andσ=(0.24±0.05) mb respectively. The two reactions are analysed in the different LPS configurations. The dσ/dt′ distribution for the two reactions displays the same exp[−At′] shape withA⋍37 (GeV/c)−2 in both cases, thus indicating that the differential cross-sections are dominated by the deuteron form factor. The coherent inclastic interaction contains the channel π+d → θ0π+d with a cross-sectionσ==(20±5) µb and a signal for the B+-meson of about 12 µb. The four-pion masses display structures below 2 GeV/c.RiassuntoNella camera a bolle 2 m DBC del CERN esposta ad un fascio di π+ di 11.7 GeV/c si sono studiate le due interazioni coerenti π+d → π+π+π−d e π+d → π+π+π−π0d. Le sezioni d’urto di produzione sono rispettivamenteσ=(0.37±0.06) mb eσ=(0.24±0.05) mb. Si analizzano diversi aspetti dei due canali esclusivi tra cui le diverse configurazioni longitudinali più frequenti. La sezione d’urto differenziale dσ/dt′ presenta la stessa forma exp [−At′] con un valoreA⋍37 (GeV/c)−2 per entrambe le reazioni. Ciò implica la dominanza del fattore di forma del deutone su entrambi i processi in esame. La reazione coerente inelastica contiene un contributoσ=(20±5) µb del canale π+d → θ0π+d nel quale il segnale del mesone B+ è di circa 12 µb. Le masse effettive di quattro pioni mostrano strutture tipiche e significative perM∼2 GeV.РеэюмеИсследуются две когерентных реакции π+d → dπ+π−π+ и π+d → dπ+π−π+π0 в 2 м дейтериевой пуэырьковой камере при импульсе падающих частиц 11.7 ГзВ/с. Иэмеренные поперечные сечения рождения соответственно составляютσ=(0.37±±0.06))μб иσ=(0.24±0.05)μб. Исследуемые две реакции аналиэируются в раэли-чных LРS конфигурациях. Распределение dσ/dt′ для двух реакций обнаруживают ту же форму ехр [−At′] сA=37 (ГзВ/с)−2 в обоих случаях. Этот реэультат укаэы-вает, что дифференциальные поперечные сечения доминируют эа счет форм-фактора дейтрона. Когерентное неупругое вэаимодействие содержит канал π+d → ω0π+d с поперечным сечениемσ=(20±5)μб и сигнал для меэона В+ с величиной около 12μб. Эффективные массы четырех пионов обнаруживают типичную структуру дляM≼2ГзВ.