Evidence for the ground state of the neutron-unbound nucleus 26 O was observed for the first time in the single proton-knockout reaction from a 82 MeV/u 27 F beam. Neutrons were measured in coincidence with 24 O fragments. 26 O was determined to be unbound by 150 +50 −150 keV from the observation of low-energy neutrons. This result agrees with recent shell model calculations based on microscopic two-and three-nucleon forces.A major challenge in nuclear physics remains the description of nuclei based on fundamental interactions. "Ab-initio" approaches have been developed to calculate nuclear properties based on nucleon-nucleon scattering data up to A ∼ 12 [1]. Recent advances in nuclear theory made it possible to describe some fundamental properties of light nuclei up to oxygen based on two-and three-nucleon interactions [2][3][4][5][6]. On the way to heavier nuclides it will be critical for these models to describe the dramatic change in the location of the neutron dripline from oxygen (N = 16) to fluorine (N ≥ 22) which was first pointed out by Sakurai et al. [7]. The addition of one proton binds at least six additional neutrons. The two-neutron separation energy of 26 O serves as an important benchmark for these calculations. The majority of the current nuclear structure models predict 26 O to be bound [8][9][10][11][12][13] respect to two-neutron emission. 26 O is thus also an excellent candidate for di-neutron emission. Furthermore calculations by Grigorenko et al. predict that the emission of a pair of correlated neutrons might be hindered so that for very low decay energies lifetimes on the order of pico-to nanoseconds could be possible [27].We searched for unbound states in 26 O using oneproton knockout reactions from 27 F and by measuring neutrons in coincidence with 24 O fragments. Figure 1 shows a schematic level scheme of the possible decay paths for predicted states of 26 O. In this letter we present the first evidence for the observation of the unbound ground state of 26 O.

This paper provides an improved estimate of CO2‐EOR (where CO2 is carbon dioxide and EOR is enhanced oil recovery) and CO2 storage potential for depleted oil fields in Michigan's northern pinnacle reef trend (NPRT). Our methodology is based on capturing data on reservoir performance from reefs currently undergoing CO2‐EOR operations in the NPRT (referred to as ‘monitored reefs’), and then applying them to other reefs within the NPRT (referred to as ‘catalog reefs’). For each monitored reef, we calculate fractional primary recovery, fractional incremental EOR recovery, net utilization ratio, and storage efficiency factor. The corresponding incremental oil recovery from EOR, storage capacity until end of EOR, and total CO2 injection needs are then estimated for each catalog reef and combined (over all monitored reefs) using a weighted averaging procedure. These weights are related to a statistical similarity measure that is calculated between each monitored reef and each catalog reef based on a number of variables related to production data, formation type, or descriptive geologic attributes. For the entire NPRT catalog of 383 reefs as used in this study, our results indicate 118 million (MM) stock tank barrels (STB) (1.88 × 107 Sm3) of incremental oil from EOR operations, corresponding to 49 MM metric tons (MT) of CO2 storage and 266 MM MT of total CO2 injection. However, approximately one‐third of the reefs provide two‐thirds of the potential for CO2‐EOR and geologic storage, assuming an economic threshold of 0.5 MM STB (80 000 Sm3) of incremental oil from EOR. © 2020 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.

No abstract

No abstract

No abstract