Xn Channels Research Articles

Comprehension of breakup fusion reactions using forward recoil range distribution measurements

To understand the break-up fusion reaction dynamics, the forward recoil range distribution (FRRD) measurements of 12C + 165Ho system at the incident projectile energy of ≈ 88 MeV has been performed. The recoil catcher activation technique followed by the off-line gamma ray spectroscopy was implemented. It is observed that the FRRD measurements of the evaporation residues (ERs) populated via xn and pxn channels have a single Guassian peak at large cumulative thickness. This is attributed to complete momentum transfer from the projectile to the target nucleus. However, in case of the FRRD measurements of the ERs populated via αxn, αpxn and 2αxn emitting channels, in addition to peak corresponding to complete momentum transfer, the Gaussian peaks at lower cumulative thicknesses are also observed. This is accredited to the breakup fusion. Moreover, the effect of projectile breakup on complete fusion cross section is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function, thus indicating the breakup probability of 12C projectile.

Growth and mobility characterization of N-polar AlGaN channel high electron mobility transistors

All-AlGaN based high electron mobility transistors (HEMTs) are promising for increasing the power density in both RF and power devices, improving overall efficiency. Nitrogen (N) polar GaN/AlGaN HEMTs offer lower contact resistance compared to its metal-polar counterpart. In this work, we report the metal organic chemical vapor deposition (MOCVD)-based growth of N-polar AlGaN channel HEMT structures with a varying Al mole fraction in the AlxGa1−xN channel (x = 20%, 30%, 59%, and 73%). We confirmed the high-quality morphology and the Al composition of the grown structures using atomic force microscopy and x-ray diffraction spectra, respectively. We measured a mobility of ∼160 cm2/(V.s) in our N-polar AlGaN HEMT stack (20% Al in the channel) structure and found an alloy-scattering dominated transport with increasing Al mole fraction, further supported by our simulations that consider both alloy-scattering and optical phonon-scattering mechanisms. From 20% to 59% Al composition, we found a decreasing trend in mobility while for 59%–73% Al composition in the channel, both the simulated and the experimental mobility showed a nearly saturating trend. The structures were then fabricated into HEMTs with Al0.20Ga0.80N (channel)/Al0.59Ga0.41N (barrier), showing 320 mA/mm drain current for a 4 μm long-channel device.

Tuning composition in graded AlGaN channel HEMTs toward improved linearity for low-noise radio-frequency amplifiers

Compositionally graded channel AlGaN/GaN high electron mobility transistors (HEMTs) offer a promising route to improve device linearity, which is necessary for low-noise radio-frequency amplifiers. In this work, we demonstrate different grading profiles of a 10-nm-thick AlxGa1−xN channel from x = 0 to x = 0.1 using hot-wall metal-organic chemical vapor deposition (MOCVD). The growth process is developed by optimizing the channel grading and the channel-to-barrier transition. For this purpose, the Al-profiles and the interface sharpness, as determined from scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy, are correlated with specific MOCVD process parameters. The results are linked to the channel properties (electron density, electron mobility, and sheet resistance) obtained by contactless Hall and terahertz optical Hall effect measurements coupled with simulations from solving self-consistently Poisson and Schrödinger equations. The impact of incorporating a thin AlN interlayer between the graded channel and the barrier layer on the HEMT properties is investigated and discussed. The optimized graded channel HEMT structure is found to have similarly high electron density (∼ 9 × 10 12 cm−2) as the non-graded conventional structure, though the mobility drops from ∼ 2360 cm2/V s in the conventional to ∼ 960 cm2/V s in the graded structure. The transconductance gm of the linearly graded channel HEMTs is shown to be flatter with smaller g m ′ and g m ″ as compared to the conventional non-graded channel HEMT implying improved device linearity.

Disentangling complete and incomplete fusion events in 12C + 169Tm reaction by spin-distribution measurements

The spin-distributions of different reaction products populated via x n and α/2αx n channels in + system have been measured at E lab ≈ 6, 7 and 7.5 MeV A−1 to disentangle complete and incomplete fusion events. Particle (p, α)-γ-coincidences were recorded to identify evaporation residues channel-by-channel. The spin-distributions of fusion evaporation and direct-α-emitting channels are found to be distinct corroborating the involvement of entirely different reaction dynamics in their production, respectively termed as complete (CF) and incomplete fusion (ICF). The values of mean input angular momenta, obtained from the analysis of the spin-distributions, involved in ICF-α/2α xn channels are estimated to be larger than that observed in CF-xn/α xn channels. For ICF-α/2αxn channels, the multiplicity of fast-α particle emission increases with the magnitude of input angular momentum imparted into the system. The CF residues display a population of broad spin range while the ICF residues are confined to a narrow spin range generally localized in the higher spin states. Findings of the present work conclusively demonstrate the possibility to populate high spin states in final reaction products using ICF, which are otherwise not accessible. Further, an attempt has been made to study the variation of input angular momentum with the choice of different entrance-channel parameters. It has been observed that the value of input angular momentum involved in ICF-α/2α xn channels increases with the deformation and entrance-channel mass-asymmetry parameter, indicating strong entrance-channel dependence of ICF dynamics.

Temperature characteristics of high-current UWBG enhancement and depletion mode AlGaN-channel MOSHFETs

We present the temperature-dependent electrical characteristics of high-current depletion (D-mode) and barrier-recessed enhancement-mode (E-mode) ultrawide bandgap (UWBG) AlxGa1−xN channel insulated gate heterojunction field-effect transistors fabricated on the same wafer. The key motivation is the higher Baliga figure of merit for devices with the UWBG AlGaN channel and their strong potential for use in high-power, high-temperature harsh environmental applications. Over a temperature range of 125 °C, the VTH shifted in the opposite direction for D- and E-mode devices with a rate of +13.5 mV/K and −23 mV/K, respectively, giving an overall shift of +1.7 V and −2.9 V. This was attributed to changes in the fixed and trapped charge densities in the dielectric and at the dielectric–AlGaN barrier interface. A single deep sub-bandgap trap level was sufficient to explain the threshold shifts in both devices. The effective channel mobility in the E-mode devices was argued to be limited by charge scattering, arising from the same charges introduced during barrier recessing that shifted VTH.

The Probable Projectile-Target Reactions to Synthesize SHE 304–312,314124 and the Predictions of α Decay Chains

The probable projectile-target reactions to synthesize SHE, Z = 124, are identified as 58Fe+248-254Cf, 64Ni+240–248,250Cm, 70Zn+236–242,244Pu, 76Ge+232–236,238U, and 82Se+228–230,232Th leading to 304–312,314124. The ER excitation functions in xn (x = 1 to 5 for hot fusion and x = 1 to 2 for cold fusion) evaporation channel are calculated. The sums of all xn channel ER cross-sections are listed and predicted the most suitable combinations. It is observed that the compound nucleus having neutron number up to N = 184 have finite ER cross-section values and we conclude that the CN having neutron number N > 184 could not be synthesized in the laboratory in near future. We have also studied the alpha decay properties of the isotopes mentioned above using modified generalized liquid drop model (MGLDM). In our study, 4α chains were observed for 304124, 3α chains observed for 305124, 6α chains observed for 306–307124, and 5α chains observed for 308–312, 314124.

High‐Temperature Operation of AlxGa1−xN (x > 0.4) Channel Metal Oxide Semiconductor Heterostructure Field Effect Transistors with High‐k Atomic Layer Deposited Gate Oxides

Due to their superior breakdown fields compared with GaN and SiC and high thermal conductivity, AlxGa1−xN (x > 0.4) channel high‐electron‐mobility transistors (HEMTs) will find applications in extreme environments such as power electronics. Herein, the high‐temperature operation of ultrawide‐bandgap (UWBG) Al0.65Ga0.35N/Al0.4Ga0.6N metal oxide semiconductor heterostructure field effect transistors (MOSHFETs) with atomic layer‐deposited (ALD) high‐k gate dielectrics TiO2, Al2O3, and ZrO2 is reported. As compared with similar geometry HFETs, these devices exhibit a simultaneous reduction in gate‐leakage current by ≈104 and a positive shift of the threshold voltage as much as 4 V. This positive threshold shift indicates the introduction of negative charges at the oxide/barrier interface and within the thin oxide, attributed to the pre‐ALD plasma treatment. The gate leakage increases weakly with temperature up to 250 °C, whereas the peak drain currents decrease from ≈0.5 to 0.3 A mm−1. An analysis of the C–V and I–V characteristics reveals that this drain current decrease is due to a reduction in channel electron mobility. The potential mechanisms responsible for this are discussed. Up to the measured temperature of 250 °C, the devices withstand repeated temperature cycles without catastrophic degradation or breakdown, underscoring the promise of these materials.

Systematic study of incomplete fusion reactions: Role of various entrance channel parameters

The evaporation residues, populated through complete and incomplete fusion processes in the reaction of 18O+ 165Ho, have been analyzed via excitation function measurements at projectile energies ≈ 4-7 MeV/nucleon. The cross-sections measured experimentally have been compared with the predictions of the compound nucleus model code PACE-4 calculations which only considers complete fusion (CF) reaction cross-sections. The experimental cross-section of the reaction residues populated through xn and pxn channels matches well with the theoretical model code PACE-4 predictions. On the other hand, α-emitting channels show an enhancement in the measured cross-section over PACE-4 calculations which reveals the occurrence of incomplete fusion (ICF) at the studied energy range. The relative percentage of incomplete fusion has been calculated from the experimental data and its dependence on various entrance channel parameters like projectile energy, mass-asymmetry, α-Q value and Coulomb factor (ZPZT) has been studied. The strength of incomplete fusion function obtained in the 18O+ 165Ho interaction has been compared with the previously studied systems. Results of the present study indicate that 18O (two neutron excess) projectile shows more incomplete fusion contribution as compared to 12C,13C and 16O projectiles due to its relatively small negative α-Q value.

Effect of projectile breakup in the system 19F + 154Sm

An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19 F + 154 Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19 F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles.

Systematic study of the break-up fusion process in the C12+Ho165 system and interplay of entrance channel parameters

To understand the low-energy incomplete fusion (ICF) reaction dynamics, the excitation function measurements of $^{12}\mathrm{C}+^{165}\mathrm{Ho}$ system has been performed in the energy region of \ensuremath{\approx} 4--7 MeV/nucleon, by employing the stacked foil activation technique. The cross sections of the measured evaporation residues are compared with the theoretical predictions of statistical model code PACE4, which takes into account only the complete fusion (CF) reaction cross section. It is observed that residues populated via xn and pxn channels are in good agreement with the PACE4 predictions, implying that these residues are populated via CF process. However, in the case of \ensuremath{\alpha}-emission channels a significant enhancement from the PACE4 predictions is observed even after the deduction of precursor contribution, which is accredited to ICF process. The projectile break-up probability is found to increase with increment in the incident projectile energy. Further, the dependence of incomplete fusion dynamics on entrance channel parameters like mass asymmetry, Coulomb effect (${Z}_{\mathrm{P}}{Z}_{\mathrm{T}}$), and projectile ${Q}_{\ensuremath{\alpha}}$ value is systematically studied. The present results reveal that a single entrance channel parameter does not oversee the ICF reaction dynamics but have varying contributions depending upon the projectile-target combination. Moreover, the effect of projectile break-up on complete fusion cross section at energies above the Coulomb barrier is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function.

Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors

In this letter, we design and demonstrate an improved metalorganic chemical vapor deposition (MOCVD) grown reverse Al-composition graded contact layer, whereby the Al-composition of AlxGa1−xN in the contact layer is graded from the higher Al-composition as in the channel to lower Al-composition, to achieve a low resistance contact to MOCVD grown ultrawide bandgap Al0.70Ga0.30N channel metal-semiconductor field-effect transistors. Increasing the thickness of the reverse graded layer was found to improve contact layer resistance significantly, leading to a contact resistivity of 3.3 × 10−5 Ω cm2. Devices with a gate length, LG, of 0.6 μm and a source-drain spacing, LSD, of 1.5 μm displayed a maximum current density, IDS,MAX, of 635 mA/mm with an applied gate voltage, VGS, of +2 V. Breakdown measurements on transistors with a gate to drain spacing, LGD, of 770 nm had breakdown voltage greater than 220 V, corresponding to a minimum breakdown field of 2.86 MV/cm—almost 3× higher than that exhibited by lateral GaN channel devices with similar dimensions. This work provides a framework for the design of low resistance contacts to MOCVD grown high Al-content AlxGa1−xN channel transistors.

Measurement of the Production Cross Sections for Isotopes of Transfermium Elements in Complete Fusion Reactions with the Subsequent Evaporation of a Proton and Neutrons

Experiments aimed at synthesizing and investigating the features of radioactive decay of isotopes of superheavy elements (Z ≥ 110) have been conducted in the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research. Complete fusion reactions of an accelerated beam of 48Ca ions with transactinide targets with the subsequent evaporation of several neutrons from excited compound nucleus are typically used in these experiments. “Exotic” reaction channels with the evaporation of protons and several neutrons may be used to produce more neutron-rich isotopes of superheavy elements. The production cross sections were measured in experiments at the SHELS separator for Db and Rf isotopes produced in xn and pxn channels of the 50Ti + 209Bi → 259Db* reaction. The ratio of cross sections σ(xn)/σ(pxn) was on the order of 100.

Ultra-wide band gap AlGaN polarization-doped field effect transistor

Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped AlxGa1−xN channel layer graded over Al compositions 0.70 ≤ x ≤ 0.85 and ohmic contact formation to the Al0.85Ga0.15N surface. Current density of 24 mA/mm was attained for a modest threshold voltage of −3.95 V owing to the high sheet charge concentration (ns) of 5.4 × 1012 cm−2 and average electron mobility (μ) of 210 cm2 V−1 s−1 for the channel region along with ohmic contacts with a specific contact resistivity of 1.1 mΩ cm2 and a large Schottky barrier height of 3.0 eV for the metal–semiconductor gate. The combination of ultra-wide band gap energy, high μ, and high ns, linear ohmic contacts, and large Schottky barrier for AlGaN PolFETs makes them attractive for both high voltage switches and high power rf devices.

Fusion-Barrier Distributions Will Unveil Most Probable Reaction Energies to Synthesize Isotopes of Superheavy Elements Beyond Z = 118

To investigate the correlations between barrier distributions and excitation functions of neutron-evaporation channels (xn channels) in nuclear reactions, researchers have measured fusion-barrier distributions in reaction systems in which superheavy isotopes are synthesized. They found that the excitation functions of 3n and 4n channels in the system 48Ca+248Cm are strongly affected by the deformation of the target nucleus. This finding will enhance our ability to quantitatively predict the most probable reaction energies for further searches of superheavy elements.

Study of incomplete fusion reaction dynamics in [formula omitted] system and its dependence on various entrance channel parameters

The excitation functions for the evaporation residues populated in the interaction of C13+165Ho system have been measured at projectile energies ≈ 4–7 MeV/nucleon. Stacked foil activation technique followed by off-line γ-ray spectroscopy have been employed in the present work. The experimentally measured cross-sections are analyzed in the frame work of statistical model code PACE4, which takes into account only the complete fusion reaction cross-sections. The evaporation residues populated via xn and pxn channels were found to be in good agreement with the PACE4 predictions, while a significant enhancement in the measured cross-sections over PACE4 predictions is observed in case of α-emitting channels, which may be attributed to the incomplete fusion process. For the better understanding of incomplete fusion dynamics, the incomplete fusion fraction has also been deduced and its sensitivity with various entrance channel parameters like: projectile energy, mass-asymmetry, projectile structure in terms of Qα-value and Coulomb effect has been studied in the present work. The incomplete fusion fraction is found to increase with increasing the projectile energy and a strong projectile structure dependent mass-asymmetry systematic is also observed. The incomplete fusion fraction is also found to be small for more negative Qα-value projectile (13C) induced reactions as compared to less negative Qα-value projectiles (12C, 16O and 20Ne) induced reactions with the same target nucleus 165Ho. An interesting trend is obtained on further investigation of incomplete fusion dependence on Coulomb effect (ZPZT).

Influence of incomplete fusion on complete fusion at energies above the Coulomb barrier

In the present work, excitation functions of several reaction residues in the system 19F+169Tm, populated via the complete and incomplete fusion processes, have been measured using off-line γ-ray spectroscopy. The analysis of excitation functions has been done within the framework of statistical model code pace4. The excitation functions of residues populated via xn and pxn channels are found to be in good agreement with those estimated by the theoretical model code, which confirms the production of these residues solely via complete fusion process. However, a significant enhancement has been observed in the cross-sections of residues involving α-emitting channels as compared to the theoretical predictions. The observed enhancement in the cross-sections has been attributed to the incomplete fusion processes. In order to have a better insight into the onset and strength of incomplete fusion, the incomplete fusion strength function has been deduced. At present, there is no theoretical model available which can satisfactorily explain the incomplete fusion reaction data at energies ≈4–6 MeV/nucleon. In the present work, the influence of incomplete fusion on complete fusion in the 19F+169Tm system has also been studied. The measured cross-section data may be important for the development of reactor technology as well. It has been found that the incomplete fusion strength function strongly depends on the α-Q value of the projectile, which is found to be in good agreement with the existing literature data. The analysis strongly supports the projectile-dependent mass-asymmetry systematics. In order to study the influence of Coulomb effect () on incomplete fusion, the deduced strength function for the present work is compared with the nearby projectile–target combinations. The incomplete fusion strength function is found to increase linearly with , indicating a strong influence of Coulomb effect in the incomplete fusion reactions.

AlGaN devices and growth of device structures

The structure of a number of GaN/AlGaN devices and their associated material growth and processing issues are examined in some detail, and extrapolations are made to predict what the advantages and challenges would accrue for similar AlGaN electrical and optical devices. For RF HEMTs, it is likely that the advantages of the larger breakdown voltage (V B) in an Al Y Ga1−Y N/Al X Ga1−X N AlGaN channel HEMT would be outweighed by the disadvantages of the lower frequency of operation created by the smaller channel mobility when compared to AlGaAs/GaAs HEMTs. The same thing can be said for lateral high-power electronic HEMTs because AlGaN/GaN HEMTs with GaN channels can now be fabricated with V B ~ 2,000 V, which is thought to be the upper voltage limit for them, even when the device structures are grown on Si substrates with its accompanying high dislocation density and bow. However, theory suggests that using Al Y Ga1−Y N/Al X Ga1−X N structures in vertical transistors and AlGaN P–N diodes could enable pulsed power applications such as electric armor because they should be able to handle an order of magnitude more power due to their ten times larger breakdown field in ~80 % Al AlGaN, and the Si donor is still relatively shallow at this Al concentration. The major challenges to achieving these goals are to be able to controllably dope the AlGaN in the mid 1015 cm−3 range, create an AlGaN current blocking layer beneath the Al Y Ga1−Y N/Al X Ga1−X N channel that contains an aperture to the drain, confine most of the mismatch dislocations in the AlGaN layers to near the interface with the GaN or AlN substrate that is parallel to the (0001) plane, and fabricate ohmic contacts to the AlGaN with a specific contact resistance <10−2 Ω cm2. Theoretically, the latter can be achieved using polarization doping. For applications to optical device structures, reducing the threading dislocation density in AlN layers on sapphire substrates by high temperature epitaxy is a key parameter for achieving AlGaN-based light emitters with a high efficiency. Stress control and prevention of relaxation is important for obtaining AlGaN layers with a similar dislocation density as the underlying AlN template. A dislocation density below 5 × 108 cm−2 is sufficient for obtaining an efficiency of radiative recombination of 40 % and higher at moderate excitation levels.

Effect of the Target Deformation on Incomplete Fusion Dynamics

To investigate the role of target deformation on incomplete fusion dynamics, a particle-gamma coincidence experiment has been performed at Inter University Accelerator Centre, New Delhi. Spin distributions for various evaporation residues populated via complete and incomplete fusion of 16 O with 124 Sn at 6.3MeV/nucleon have been measured. Experimentally measured spin distributions of the residues produced as incomplete fusion products associated with fast α and 2α-emission channels observed in forward cone are found to be distinctly different from those of the residues produced as complete fusion products. The mean value of input angular momentum J0 for evaporation residues produced through xn channels (complete fusion products) is found to be J0 ≈ 7ħ, while the mean value of input angular momentum J0 for the residues produced through direct αxn and 2αxn channels (incomplete fusion products) in forward cone, are found to be J0 ≈ 9ħ and ≈ 12ħ respectively for 16 O + 124 Sn (spherical) system [7]. The mean value of input angular momentum J0 for the system 16 O + 169 Tm (deformed) reported in ref. [8], are found to be ≈10ħ for xn-channels (complete fusion products) and for direct αxn and 2αxn channels (incomplete fusion products) the value of J0 approaches to ≈ 13ħ and ≈16ħ, respectively. The mean values of the input angular momentum observed for xn (complete fusion products), αxn and 2αxn (incomplete fusion products) in 16 O + 124 Sn (spherical) system are smaller than that of the mean values of the input angular momentum observed for xn (complete fusion products), αxn and 2αxn (incomplete fusion products) in 16 O + 169 Tm (deformed) system. The comparison of data inferred that the mean values of the input angular momentum are smaller in case of spherical target than that of deformed target at same projectile energy of 16 O-ion beam. It means that the target deformation affect the incomplete fusion dynamics.

Incomplete fusion reactions at low energies in13C+169Tm system

Aiming to investigate the incomplete fusion processes at low projectile energies, experiments have been carried out for the 13 C + 169 Tm system at ≈ 4-7 MeV/A. Excitation functions for several heavy residues likely to be populated via complete and incomplete fusion processes have been measured using heavy recoil residue catcher technique followed by γ - ray spectroscopy. The measured cross-sections for the complete fusion (xn and pxn ) channels are compared with the statistical model code PACE4, consistently using the same set of parameters. The complete fusion channels are found to be consistent with the model calculations. However, the cross-sections for all the measured α-emitting channels are found to be significantly enhanced over the calculations. Analysis of data indicate a significant fraction of incomplete fusion even at energies as low as 17% above barrier. The present results are discussed in light of the Morgenstern’s systematics. Incomplete fusion strength function is found to be relatively large for alpha cluster projectile i.e. for 12 C as compared to one neutron excess 13 C projectile.

Observation of entrance channel mass-asymmetry effect on incomplete fusion reaction for system

Abstract An experiment has been performed to explore the incomplete fusion (ICF) reaction dynamics in heavy ion induced reactions. Excitation functions (EFs) for eighteen evaporation residues (ERs) produced in the system Ne 20 + Ho 165 have been measured in the energy range ≈ 88 – 164 MeV . Some of the ERs have significant contribution from precursor decay, which has been separated out from the measured cumulative cross-sections to get direct production cross-sections. Parameters of the statistical model code PACE-2 are optimized to reproduce the ERs populated in complete fusion reactions such as in xn and pxn channels. Using the same parameters, EFs for the residues produced in α-particle(s) emission channels have been calculated. A significant enhancement in the measured EFs of the ERs produced in α-particle(s) emission channels over the PACE-2 predictions have been observed which indicates the occurrence of incomplete fusion reaction process. In the ICF process the break-up of projectile 20Ne into He 4 + O 16 and/or Be 8 + C 12 takes place followed by fusion of one of the fragments with the target nucleus 165Ho. The present data analyses suggest that probability of incomplete fusion reaction increases with projectile energy. The ICF fraction F ICF has been estimated and found to increase with increasing mass-asymmetry [ A T / ( A T + A P ) ] of the partners in entrance channel. It is also observed that critical angular momentum associated with incomplete fusion channels at higher projectile energy may be associated with l-values lower than that of peripheral collisions, indicating that the incomplete fusion competes with complete fusion even at angular momentum values little lower than critical angular momentum.