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An array of eight CsI(Tl) detectors has been set up to measure the light charged particles in nuclear reactions using heavy ions from the Pelletron Linac Facility, Mumbai. The energy response of CsI(Tl) detector to α -particles from 5 to 40 MeV is measured using radioactive sources and the 12C(12C, α ) reaction populating discrete states in 20Ne. The energy non-linearity and the count rate effect on the pulse shape discrimination property have also been measured and observed the deterioration of pulse shape discrimination with higher count rate.

To disentangle the role of shell effects and dynamics, fission fragment mass distributions of 191Au, a nucleus in the newly identified island of mass asymmetric fission in the sub-lead region, have been measured down to excitation energy of ≈20 MeV above the fission barrier via two different entrance channels, viz. 16O+175Lu and 37Cl+154Sm reactions. Apart from having signature of the shell effects in both the cases, clear experimental evidence of quasifission has been observed in the mass distributions of the Cl induced reaction, that has also been substantiated by the theoretical calculations. This crucial evidence along with a systematic analysis of the available experimental data has revealed that the dynamics in the entrance channel has significant influence on most of the reactions used earlier to explore the persistence of recently discovered mass asymmetry in β-delayed fission at low energy in this mass region, ignoring which might lead to ambiguity in interpreting the heavy-ion data. Keywords: Fusion-fission, Mass asymmetric fission, Shell effects, Quasifission

Elastic-scattering angular distributions were measured for the $^{7}\mathrm{Li}+^{159}\mathrm{Tb}$ system at various energies; namely, 24, 26, 28, 30, 35, 40, and 44 MeV. The optical-model analysis was performed to investigate the energy dependence of real and imaginary potentials, employing a Woods--Saxon form of potential. The dispersion-relation analysis were also carried out to check the consistency of real and imaginary parts of the potentials. The energy dependence of real and imaginary potentials does not follow the trend of conventional threshold anomaly but rather represents unusual behavior of the increase of imaginary part of the potential and corresponding decrease in real part of the potential near the Coulomb barrier energy. The effect of breakup coupling on elastic-scattering angular distributions was studied by a continuum-discretized coupled-channels (CDCC) calculation. The behavior of dynamic polarization potentials obtained due to the breakup coupling is discussed. The total reaction cross sections for the present and various other systems are also compared involving $^{7}\mathrm{Li}$ projectile on different target nuclei in the mass range $A=16$ to 232.

Gamma ray spectra in the energy range of ∼4–25 MeV were measured in the reaction 28 Si + 124 Sn at E ( 28 Si) ∼ 150 MeV in coincidence with low energy γ -multiplicities. The spectra were analysed using a simulated Monte Carlo CASCADE code. The centroid energy and width of the giant dipole resonance were extracted for various multiplicity windows. The average angular momentum and temperature of the final states populated after the giant dipole photon emission range from ∼25 ℏ and 1.5 MeV to ∼56 ℏ and 1.3 MeV, respectively. The extracted widths are almost constant for the lower multiplicity windows and show an increase of ∼1.4 MeV at the highest window. The nuclei are expected to be near the liquid drop regime and the experimental results are not inconsistent with the liquid drop behaviour.

Gamma multiplicity gated proton spectra have been measured in the 12C + 93Nb reaction at E ( C 12 ) = 40 MeV at backward angles. The shape of the spectrum shows a drastic change with the increase in multiplicity acquiring a broad structure at proton energies beyond ∼ 15 MeV corroborating our earlier measurements at E ( C 12 ) = 42.5 MeV . Measurements made in coincidence with residue γ rays, detected in an array of eight HPGe clover detectors, confirm these observations. An excitation energy and angular momentum-dependent enhancement of the nuclear level density or a massive cluster transfer of 11B to the 93Nb can explain the data.

Proton and alpha spectra in the energy range E p c.m. ∼6 –24 MeV and E α c.m. ∼12 –40 MeV, respectively, have been measured in the reaction 28 Si + 58 Ni at E lab ( 28 Si )=100 and 125 MeV. The spectra at various laboratory angles from 100° to 160° were corrected for angular distribution effects to obtain the angle-integrated spectra. An asymptotic (liquid drop) level density parameter of a =A/7.5 describes the proton and alpha spectra at both the beam energies. No lowering of emission barrier is needed to explain the alpha spectra although the spin dependence of level density has to be tuned. The derived value of a is somewhat larger than that for other near-stable nuclei and possibly arises due to the excitation energy dependent collective enhancement of the nuclear level density.

High-energy proton spectra in the energy range E p c.m. ∼8.5–25 MeV are measured in the reaction 12 C+ 93 Nb at E lab ( 12 C)=42.5 MeV and at laboratory angles of 130°, 145° and 160°. The spectra, recorded in coincidence with a gamma ray multiplicity detector array, show a broad structure which becomes more prominent at higher multiplicity. The centroid of the structure shifts with multiplicity. These features could arise from an unusual spin and excitation energy dependence of the nuclear level density in Pd and Ag nuclei with mass around A =104. However, a non-statistical process, viz. , the massive cluster transfer, cannot be ruled out.

A compact array of seven hexagonal BaF2 detectors, with cosmic ray background suppression, has been set up for the measurement of high energy photons up to ∼30 MeV. The array has been used in the measurement of giant dipole photons in low energy heavy-ion reactions.

The effects of breakup reactions on elastic and α-production channels for the 6Li+116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels (CDCC) calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials (DPP) from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of 6Li projectile with 116Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels.

The fusion barrier distributions for $^{28,30}\mathrm{Si}$ + $^{124}\mathrm{Sn}$ systems were extracted from quasielastic excitation function measurements at backward angles. The experimental barrier distributions were then compared with coupled-channel (CC) calculations. The fusion barrier distribution for the $^{30}\mathrm{Si}$ + $^{124}\mathrm{Sn}$ reaction was well reproduced by the CC calculations with the inclusion of projectile and target inelastic couplings and only one possible positive $Q$-value 2$n$-transfer channel coupling using the ccfull code. However, CC calculations with similar coupling schemes for inelastic excitation of target and projectile with the 4$n$-transfer channel corresponding to the highest positive $Q$ value failed to reproduce the barrier distribution for the $^{28}\mathrm{Si}$ + $^{124}\mathrm{Sn}$ reaction, because it has many positive $Q$-value multi-neutron transfer channels. A better agreement between the experimental fusion barrier distribution for the $^{28}\mathrm{Si}$ + $^{124}\mathrm{Sn}$ system and the prediction of semiempirical CC calculations based on the Zagrebaev framework [V. I. Zagrebaev, Phys. Rev. C 67, 061601(R) (2003)] was obtained only after considering positive $Q$-value multi-neutron transfer couplings. The sensitivity of the fusion barrier distribution to the hexadecapole deformation parameter ${\ensuremath{\beta}}_{4}$ of the projectile was also discussed.

The fission decay probabilities of the $^{235}\mathrm{Pa}$ and $^{236}\mathrm{U}$ compound nuclei produced in a single experiment in $^{232}\mathrm{Th}$($^{7}\mathrm{Li}$, $\ensuremath{\alpha}f$)$^{235}\mathrm{Pa}$ and $^{232}\mathrm{Th}$($^{7}\mathrm{Li}$, $tf$)$^{236}\mathrm{U}$ transfer induced fission reaction channels, have been measured at ${E}_{\mathrm{lab}}=39.5$ MeV in the excitation energy range of 14--20 MeV. The $^{234}\mathrm{Pa}$(n, f) cross sections are then deduced from the measured fission decay probability ratios of $^{235}\mathrm{Pa}$ and $^{236}\mathrm{U}$ compound systems in the equivalent neutron energy range of 8--14 MeV within the framework of the hybrid surrogate ratio method, considering the well-measured $^{235}\mathrm{U}$(n, f) cross sections as the reference. The experimental data on $^{234}\mathrm{Pa}$(n, f) cross sections have been compared with the calculated fission cross sections using empire-3.1 code with the fission barrier height values obtained from barrier formula (BF) as well as ripl-3 [24]. The present experimental results are found to be in very good agreement with the empire-3.1 predictions for the fission barrier heights predicted by the BF.

The excitation functions have been measured for the {sup 12}C ({sup 12}C,{alpha}){sup 20}Ne and {sup 12}C({sup 12}C,{sup 8}Be){sup 16}O reactions leading to the excited states up to 25 MeV in {sup 20}Ne and 20 MeV in {sup 16}O, respectively, in the beam energy range E({sup 12}C)=48{endash}72 MeV. The region of excitation investigated was E{sub x}=38{endash}50 MeV in {sup 24}Mg which is well above the threshold for breakup into six alpha particles. In the {sup 8}Be channel leading to the 6{endash}7 MeV region of {sup 16}O, excitation functions were also measured for {sup 8}Be- {gamma} coincidences in {sup 12}C ({sup 12}C,{sup 8}Be){sup 16}O{sup *}{r_arrow}{gamma}+{sup 16}O{sub g.s.} particularly to distinguish between the otherwise unresolved 6.05 MeV, 0{sup +} and 6.13 MeV, 3{sup {minus}} states in {sup 16}O. It is observed that a cluster of resonances in the excitation region 39{endash}43 MeV in {sup 24}Mg decays via {alpha} and {sup 8}Be channels predominantly to the particle-hole states in {sup 20}Ne and {sup 16}O which are members of deformed bands. Another cluster of resonances in the region 44{endash}49 MeV (centered at E{sub c.m.}=32.5 MeV) decays predominantly to the 20.48 MeV state in {sup 20}Ne (which is above the 5{alpha} breakup threshold) and to amore » possible 4{alpha} linear chain band in {sup 16}O around 18 MeV, indicating their highly deformed nature. This latter cluster structure coincides in energy with the possible 6{alpha} linear chain resonance identified in the literature at E{sub c.m.}=32.5 MeV in the inelastic scattering channels {sup 12}C{sub 7.65,0{sup +}}+{sup 12}C{sub 7.65,0{sup +}} and {sup 12}C{sub 7.65,0{sup +}}+{sup 12}C{sub 9.64,3{sup {minus}}}. In this excitation energy region intermediate structures in the {sup 8}Be channel are found at E{sub c.m.}=31.5 and 33.5 MeV decaying to the 6.13 MeV, 3{sup {minus}} state and at E{sub c.m.}=32.5 MeV decaying to the 6.92/7.13 MeV states of {sup 16}O. (Abstract Truncated)« less

The ${}^{241}$Pu(n,f) cross sections have been determined by the surrogate ratio method in the equivalent neutron energy range 11.0--16.0 MeV by using ${}^{238}$U(${}^{6}$Li,$d$)${}^{242}$Pu and ${}^{232}$Th(${}^{6}$Li,$d$)${}^{236}$U transfer reactions at E${}_{\text{lab}}=39.6$ and 39.0 MeV, respectively. Results have been compared with direct measurement of ${}^{241}$Pu(n,f) cross-section data and predictions of statistical model code empire 3.1 for different sets of values of fission barrier heights from evaluated data libraries. The present ${}^{241}$Pu(n, f) cross-section data are observed to be consistent with the direct measurements, suggesting the applicability of surrogate methods. However, the empire 3.1 predictions are not in complete agreement with the experimental data in the neutron energy range 2.0--20.0 MeV for any set of the fission barrier data libraries. The consistency of experimental results on ${}^{241}$Pu(n,f) cross section data from direct and surrogate measurements suggests the need for fission barrier heights for Pu isotopes that are different from those used in standard libraries. The fission barrier heights for various Pu isotopes have been obtained for best fit to the experimental data in the neutron energy range 2.0--20.0 MeV.

Proton yields in the energy range of {similar_to}10--30 MeV have been measured in the reactions {sup 12}C+{sup 93}Nb at {ital E}({sup 12}C)=40, 45, 50, and 56 MeV and {sup 12}C+{sup 103}Rh at {ital E}({sup 12}C)=53 MeV at {theta}{sub lab}=125{degree} and 155{degree}. From these measurements the energy variation of the total nuclear level density has been extracted for {sup 104}Pd and {sup 114}Sn in the excitation-energy range of {similar_to}7--24 MeV and {similar_to}12--24 MeV, respectively. No sizable effect of the proton shell closure at {ital Z}=50 is seen at excitation energies beyond {similar_to}15 MeV though there is an indication of this effect becoming important at lower energies.

Evaporation-residue-gated high-energy gamma-ray spectra were measured in the ${}^{19}$F+${}^{27}$Al reaction at two beam energies of $\ensuremath{\sim}$75 and 125 MeV. The compound nuclear angular momenta populated at the higher energy should extend beyond the critical value for the Jacobi shape transition, while those at the lower energy should be mostly restricted below the critical value. A sharp low-energy (at $\ensuremath{\sim}$10 MeV) component has been observed in the gamma-ray strength function superimposed on a broad distribution. At the higher beam energy, the component becomes more prominent at higher angular momentum, whereas an opposite behavior is witnessed at the lower beam energy. The implication of these observations in connection with the occurrence of the Jacobi shape transition is discussed.

Elastic-scattering angular distributions of 7Li on 116Sn have been measured at different bombarding energies between 18 to 35 MeV. The effects of the weakly bound projectile breakup channel on the bombarding energy dependence of the interaction potential have been investigated. In this work we present the experimental results, along with the theoretical analysis using Woods-Saxon potential to investigate the energy dependence of the interacting polarizing potentials. Total reaction cross-sections are also presented and discussed.

We have measured the elastic scattering of the weakly bound $^{6}\mathrm{Li}$ on the $^{116,112}\mathrm{Sn}$ targets, at energies close to the Coulomb barrier. The energy dependence of the interaction potential has been investigated by two different methods and the presence of the breakup threshold anomaly is observed. We have also derived the total reaction cross sections for the above systems and compared them to those of other systems with halo, weakly bound, and tightly bound projectiles on targets with similar masses. The reaction cross sections are largest for systems with halo nuclei, then the systems with no-halo weakly bound nuclei, and the smallest cross sections are those for tightly bound systems.

Proton and {alpha}-particle spectra have been measured at backward angles in the {sup 12}C + {sup 93}Nb reaction at E({sup 12}C)=37.5-60 MeV and in the {sup 16}O+{sup 93}Nb reaction at E({sup 16}O)=54-75 MeV. The inclusive particle spectra generally are in good agreement with the statistical model calculations except for the {alpha} spectra in the {sup 12}C-induced reaction at beam energies of 37.5-42.5 MeV which are close to the Coulomb barrier in the entrance channel. In these cases the evaporation peak is up to 2 MeV lower than its expected position from the statistical model predictions. Gamma-multiplicity-gated {alpha} spectra, measured in the same reaction, also show the aforementioned discrepancy. These observations reveal that the conventional statistical model cannot explain the {alpha}-particle spectra in the {sup 12}C-induced reactions near the Coulomb barrier.

A new hybrid surrogate ratio approach has been employed to determine neutron-induced fission cross sections of $^{233}\mathrm{Pa}$ in the energy range of 11.5 to 16.5 MeV for the first time. The fission probability of $^{234}\mathrm{Pa}$ and $^{236}\mathrm{U}$ compound nuclei produced in $^{232}\mathrm{Th}$($^{6}\mathrm{Li}$, $\ensuremath{\alpha}$)$^{234}\mathrm{Pa}$ and $^{232}\mathrm{Th}$($^{6}\mathrm{Li}$, $d$)$^{236}\mathrm{U}$ transfer reaction channels has been measured at ${E}_{\mathrm{lab}}=38.0$ MeV in the excitation energy range of 17.0 to 22.0 MeV within the framework of the absolute surrogate method. The $^{233}\mathrm{Pa}$$(n,f)$ cross sections are then deduced from the measured fission decay probability ratios of $^{234}\mathrm{Pa}$ and $^{236}\mathrm{U}$ compound nuclei using the surrogate ratio method. The $^{233}\mathrm{Pa}$$(n,f)$ cross section data from the present experiment along with the data from the literature, covering the neutron energy range of 1.0 to 16.5 MeV have been compared with the predictions of statistical model code EMPIRE-2.19. While the present data are consistent with the model predictions, there is a discrepancy between the earlier experimental data and EMPIRE-2.19 predictions in the neutron energy range of 7.0 to 10.0 MeV.

The measurement of the giant electric dipole resonance built on the isobaric analog state in the self-conjugate even-even nucleus $^{12}\mathrm{C}$ is reported covering a wide excitation energy range. This is done using the $^{11}\mathrm{B}$($p,\ensuremath{\gamma}$) reaction leading to the 15.1 MeV $T=1$ state in $^{12}\mathrm{C}$ over a proton energy range of 7 to 24.5 MeV. Two resonances of 1.3 and 2 MeV widths are observed at excitation energies of 24.4 and 28.8 MeV superimposed on a smoothly varying cross section. The \ensuremath{\gamma} transitions from both the resonances are assigned $E1$ multipolarity. The structured $T=0$ component of the $E1$ strength distribution is thus very different from that built on the first $T=1$ state in the neighboring nucleus $^{14}\mathrm{N}$ and those built on the ground states of $^{12}\mathrm{C}$ and $^{14}\mathrm{C}$.

A large area plastic scintillator detector array(~ 1 m x1m) has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for mono-energetic neutrons using the 7Li(p,n1)7Be*(0.429 MeV) reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7Li(p,n1) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4-12 MeV, in the reaction 12C+ 93Nb at E(12C)= 40 MeV. This is in reasonable agreement with a statistical model calculation., Comment: 31 pages, 17 figures, submitted to NIM A

The angular distributions of cross sections for the reaction $^{13}\mathrm{C}$${(}^{3}$He${,}^{4}$He${)}^{12}$C leading to ground state and first excited 4.44 MeV, ${2}^{+}$ state of $^{12}\mathrm{C}$ have been measured at sub-Coulomb energies of ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.}$=1.20 and 1.05 MeV. The angular distributions are asymmetric with respect to 90\ifmmode^\circ\else\textdegree\fi{} and anisotropies are also found to be much larger than those expected from compound nuclear processes. Analyses of the data, with assumptions of direct transfer processes, by exact finite range distorted wave Born approximation calculations show the presence of interference of two modes of direct transfer mechanisms of neutron transfer and $^{9}\mathrm{Be}$ cluster transfer from the target $^{13}\mathrm{C}$ to the projectile $^{3}\mathrm{He}$. These direct transfer calculations are in good agreement with the angular distributions and yield the value of the ratio of three nucleon spectroscopic strengths of first excited state to ground state of $^{12}\mathrm{C}$ in good agreement with the value predicted from structure calculations.

Coulomb effects during the interaction of light deformed projectile nuclei with a heavy collision partner have been predicted to modify the fusion barrier distribution leading to a hindrance in the sub-barrier fusion cross section. In order to verify this experimentally, we have determined the fusion barrier distributions from the measurement of quasielastic excitation functions for {sup 16}O(spherical)+{sup 115}In, {sup 28}Si(oblate)+ {sup 115}In, and {sup 30}Si(prolate)+ {sup 115}In systems. For {sup 16}O+{sup 115}In system, the fusion barrier distribution is single peaked, whereas for {sup 28}Si+{sup 115}In and {sup 30}Si+{sup 115}In systems, one observes broadening and well defined structures in fusion barrier distribution, which could be explained by coupled-channel calculations performed using the CCFULL code after including deformation and Coulomb effects on the projectile in the field of target nucleus.

The radiative proton capture cross section to the $15.1\phantom{\rule{0.3em}{0ex}}\text{MeV}$ $T=1$ state in $^{12}\mathrm{C}$ has been measured in the reaction $^{11}\mathrm{B}(p,\ensuremath{\gamma})^{12}\mathrm{C}$ at the proton energies of $7.2\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and $17--24\phantom{\rule{0.3em}{0ex}}\text{MeV}$ in $1\phantom{\rule{0.3em}{0ex}}\text{MeV}$ steps. The capture $\ensuremath{\gamma}$ ray was detected in coincidence with the $15.1\phantom{\rule{0.3em}{0ex}}\text{MeV}$ $\ensuremath{\gamma}$ ray arising from the subsequent decay of the $T=1$ state to the ground state. The measured cross sections, for ${E}_{p}=17--24\phantom{\rule{0.3em}{0ex}}\text{MeV}$, are much larger than the direct capture model prediction whereas the agreement with the model is good at ${E}_{p}=7.2\phantom{\rule{0.3em}{0ex}}\text{MeV}$. A semidirect capture model, including the excitation of the giant dipole resonance on the $15.1\phantom{\rule{0.3em}{0ex}}\text{MeV}$ state, reasonably explains the data. The energy and the width of the resonance are extracted.

High-energy $\ensuremath{\gamma}$ rays in the energy range of $\ensuremath{\sim}4--35\mathrm{MeV}$ were measured in coincidence with a $\ensuremath{\gamma}$-ray multiplicity detector array in the reaction ${}^{28}\mathrm{Si}{+}^{58}\mathrm{Ni}$ at ${E(}^{28}\mathrm{Si})=100$ and 125 MeV. The data were analyzed using the statistical model, and the giant dipole resonance parameters were extracted for various multiplicity windows. The exclusive temperature dependence of the $\ensuremath{\gamma}$-ray strength function has been obtained for a wide range of angular momentum, while the angular momentum dependence has been derived over a restricted range of temperature. The observed increase in the resonance width can be attributed to an increase in temperature. No dependence on angular momentum is observed. The last observation is at variance with the results in the tin region for similar rotational frequencies.

Gamma-ray multiplicity gated proton spectra have been measured in the 12C + 93Nb and 16O + 89Y reactions producing the same compound nucleus 105Ag at an excitation energy of ~39.8 MeV, and in the 12C + 89Y reaction at E(12C) = 40 MeV. Multiplicity gated alpha particle spectra have been measured in the 12C + 93Nb reaction at E(12C) = 37.5–45 MeV. All these measurements were aimed at gaining more insight into the origin of the unexpected broad structures seen earlier in the high energy part of the proton spectra at high gamma-ray multiplicities. Two possible explanations, one of the enhanced nuclear level density within the statistical model and the other of a massive cluster transfer process, were suggested by us to understand the earlier data. The former prescription appears to be favoured by the present proton data.

The excitation functions have been measured in the energy range E/sub ..cap alpha../ = 26--37 MeV for the reaction /sup 24/Mg(/sup 4/He,/sup 12/C)/sup 16/O at theta/sub lab/ = 30/sup 0/, 40/sup 0/, and 50/sup 0/ and for /sup 24/Mg(/sup 4/He,/sup 4/He')/sup 24/Mg at theta/sub lab/ = 152/sup 0/--160/sup 0/. Prominent structures are observed in the excitation functions. The cross sections are compared with the Hauser-Feshbach statistical-model calculations. Probability distributions of the deviations from the average are calculated for all the excitation functions and compared with the statistical-model expectations for the fluctuations. The coherence width is estimated to be 176--214 keV from the observed number of maxima in the excitation functions and it is in agreement with the expected value for the excitation region of 32--42 MeV in the compound nucleus. Cross-channel correlations have been calculated between the /sup 12/C channel and alpha elastic and inelastic scattering channels. At E/sub ..cap alpha../ = 27.8 and 28.6 MeV where large cross-channel correlations have been observed, angular distributions of /sup 12/C have been measured and found to follow the pattern (P/sub 11/(costheta))/sup 2/. These results show that the excitation functions are all generally in agreement with the fluctuations expected from the statistical model.more » However, at E/sub ..cap alpha../ = 27.8 and 28.6 MeV where large cross-channel correlations are observed, though there is a small chance of less than 6 x 10/sup -4/ for these to be due to statistical fluctuations, the possibility that these structures at these two energies are nonstatistical in origin cannot also be ruled out.« less