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Today, we take international collaborations as a necessity, but 150 years ago, when travel was not so convenient, it involved an enduring and time-consuming challenge. This paper presents letters and reports written by German physicist Julius Plücker to his wife, Antonie née Altstädten describing his travels to Great Britain and France between 1853 and 1866. These letters provide a view into how international collaboration and communication were developed and maintained as well as how friendships were built within the scientific community during the early industrial age, prior to telegraph, telephone, email, and internet.

The origin of calcium production in the first stars (Pop III stars), which formed out of the primordial matter of the Big Bang, and their fates, remain most fascinating mysteries in astrophysics. Advanced nuclear burning and supernovae were thought to be the dominant source of the Ca production seen in all stars. Here we report on a qualitatively different path to Ca production through break-out from the "warm" carbon-nitrogen-oxygen (CNO) cycle. We extend direct measurement of the $^{19}$F($p$, $\gamma$)$^{20}$Ne break-out reaction down to an unprecedentedly low energy point of 186 keV and discover a key resonance at 225 keV. In the domain of astrophysical interest, at around 0.1 giga kelvin, this thermonuclear $^{19}$F($p$,$\gamma$)$^{20}$Ne rate is up to a factor of 7.4 larger than the previous recommended rate. Our stellar models show a stronger break-out during stellar hydrogen burning than thought before, and may reveal the nature of Ca production in Pop III stars imprinted on the oldest known ultra-iron poor star, SMSS0313-6708. This result from the China Jinping Underground Laboratory, the deepest laboratory in the world, offering an environment with extremely low cosmic-ray induced background, has far-reaching implications on our understanding of how the first stars evolve and die. Our rate showcases the impact that faint Pop III star supernovae can have on the nucleosynthesis observed in the oldest known stars and first galaxies, key mission targets of the James Webb Space Telescope., Comment: 32 pages, 8 figures, 6 tables

Proposed mechanisms for the production of calcium in the first stars (population III stars)-primordial stars that formed out of the matter of the Big Bang-are at odds with observations

Fluorine is one of the most interesting elements in nuclear astrophysics, where the ^{19}F(p,α)^{16}O reaction is of crucial importance for Galactic ^{19}F abundances and CNO cycle loss in first generation Population III stars. As a day-one campaign at the Jinping Underground Nuclear Astrophysics experimental facility, we report direct measurements of the essential ^{19}F(p,αγ)^{16}O reaction channel. The γ-ray yields were measured over E_{c.m.}=72.4-344 keV, covering the Gamow window; our energy of 72.4 keV is unprecedentedly low, reported here for the first time. The experiment was performed under the extremely low cosmic-ray-induced background environment of the China JinPing Underground Laboratory, one of the deepest underground laboratories in the world. The present low-energy S factors deviate significantly from previous theoretical predictions, and the uncertainties are significantly reduced. The thermonuclear ^{19}F(p,αγ)^{16}O reaction rate has been determined directly at the relevant astrophysical energies.

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed O 18 / O 16 relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions O 18 ( p , α ) N 15 and O 18 ( p , γ ) F 19 in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the ( p , γ ) reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement. Purpose: Our aim is the direct measurement of states in F 19 as populated through the reaction O 18 ( p , γ ) F 19 to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of F 19 .Method: Branchings and resonance strengths were measured in the proton energy range E p lab = 150 – 400 keV , using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity. Results: The uncertainty of the γ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the 334 keV resonance, and individual γ decays of the 215 keV resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through α emission were identified. The strengths of the observed resonances are generally in agreement with literature values. Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the O 18 ( p , γ ) F 19 reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the O 18 depletion observed in Group 2 oxygen-rich stardust grains.

This work presents results of macro, micro, and nanoscale surface characterization for a set of Roman denarii, ranging from 136 BCE to 240 CE, using large-scale X-ray fluorescence (XRF) mapping, particle-induced X-ray emission (PIXE) spectroscopy, focused-ion-beam-assisted scanning electron microscopy (FIB-SEM) with energy dispersive spectroscopy (EDS). The combination of XRF and PIXE, with varying beam energies, allowed for visualization and quantification of individual elements as a function of the surface distribution. These results helped to select suitable areas for FIB-SEM-EDS analysis. The edges of selected coins were polished to image the inner composition and surface morphology of the coins using a backscattering electron (BSE) imaging method and EDS mapping. Nanosized lamellas extracted from the coins were investigated by transmission electron microscopy (TEM) as well. The combination of these methods enabled the surface, the subsurface, and volume composition of these coins to be probed to better understand their production methods, their surface treatment methods, and their corrosion. The results also provide evidence that a particular surface treatment method, amalgam silvering, had been used to make authentic Roman coins as early as the third century CE.

First generation, or Population III, stars have a different evolution than those of later generations owing to their initial primordial abundance composition. Most notably, the lack of carbon, oxygen, and nitrogen means that primordial massive stars must rely on the less efficient p-p chains, thereby requiring the star to contract to reach temperatures high enough to eventually trigger 3α reactions. Even small amounts of the C12(α,γ)O16 reactions begin feeding the CNO mass range and enable the CNO cycle to generate energy, but this occurs at higher temperature compared to later stellar generations. It is currently controversial if the observed enhanced abundances of Ca in the most metal-poor stars could be a result of the high temperature H-burning conditions in the first massive stars. The level of this enrichment depends on the hot breakout path from the CNO cycles via the F19(p,γ)Ne20 reaction. In this work, the rates of both the F19(p,γ)Ne20 and competing F19(p,α)O16 reactions are re-evaluated using the phenomenological R-matrix approach, simultaneously considering several F19(p,γ)Ne20, F19(p,α)O16, and F19(p,p)F19 data sets, to better characterize the rate uncertainties. It is found that the rate uncertainty for F19(p,γ)Ne20 reaction is considerably larger than previously reported. This is the result of undetermined interferences between observed resonances, a possible threshold state, possible subthreshold states, direct capture, and background levels. Additional experimental measurements are therefore needed to determine if F19(p,γ)Ne20 CNO breakout is responsible for Ca enrichment in metal-poor stars. Astrophysically, the breakout reaction revision makes it less likely that Ca observed in the most Fe-poor stars can originate in hot CNO breakout H-burning nucleosynthtesis, thereby casting doubt on the prevailing faint supernova scenario to explain the abundances observed in these stars.

The CNO cycle is the main energy source in stars more massive than our sun, it defines the energy production and the cycle time that lead to the lifetime of massive stars, and it is an important tool for the determination of the age of globular clusters. One of the largest uncertainties in the CNO chain of reactions comes from the uncertainty in the $^{14}$N$(p,\gamma)^{15}$O reaction rate. This uncertainty arises predominantly from the uncertainty in the lifetime of the sub-threshold state in $^{15}$O at $E_{x}$ = 6792 keV. Previous measurements of this state's lifetime are significantly discrepant. Here, we report on a new lifetime measurement of this state, as well as the excited states in $^{15}$O at $E_{x}$ = 5181 keV and $E_{x}$ = 6172 keV, via the $^{14}$N$(p,\gamma)^{15}$O reaction at proton energies of $E_{p} = 1020$ keV and $E_{p} = 1570$ keV. The lifetimes have been determined with the Doppler-Shift Attenuation Method (DSAM) with three separate, nitrogen-implanted targets with Mo, Ta, and W backing. We obtained lifetimes from the weighted average of the three measurements, allowing us to account for systematic differences between the backing materials. For the 6792 keV state, we obtained a $\tau = 0.6 \pm 0.4$ fs. To provide cross-validation of our method, we measured the known lifetimes of the states at 5181 keV and 6172 keV to be $\tau = 7.5 \pm 3.0$ and $\tau = 0.7 \pm 0.5$ fs, respectively, which are in good agreement with previous measurements., Comment: 10 pages, 13 figures

Radiative neutron capture reactions play an important role in nuclear astrophysics. In some cases direct neutron capture reaction studies are not possible and neutron transfer reactions have been suggested as a surrogate approach. We have performed a detailed study of the $^{25}\mathrm{Mg}(d,p)^{26}\mathrm{Mg}$ reaction at a beam energy of 56 MeV as a surrogate reaction to the radiative neutron capture reaction $^{25}\mathrm{Mg}(n,\ensuremath{\gamma})^{26}\mathrm{Mg}$. A large number of neutron bound and unbound states between 10.6 and 12.1 MeV excitation energy in $^{26}\mathrm{Mg}$ were observed. Angular distribution analysis provided information about the orbital momentum transfer populating these levels. The comparison with resonances observed in the $^{25}\mathrm{Mg}(n,\ensuremath{\gamma})^{26}\mathrm{Mg}$ reaction indicate that different levels in $^{26}\mathrm{Mg}$ are being populated through the two reaction mechanisms, causing substantial discrepancies in the reaction-rate prediction. This result demonstrates that neutron transfer reaction studies may not necessarily lead to reliable predictions for neutron capture reaction rates.

This chapter describes the origins and development of Emma Beatrice Huber. Emma spent the war as a college girl and a nun in hiding, in the United States. She returned to Europe to seek a theater and design career.

Emma Beatrice Haas was left without income after Arthur’s death. Using her skills in multiple languages, she first worked at the Notre Dame Archives and from there she transferred to the National Archives in Washington. She was recruited by the OSS and subsequently by the CIA and had a successful career in identifying Nazi criminals in hiding, during the first years after the war. She continued to serve and while closer details were not disclosed by the CIA archives, her personal letter and postcard collection reveals that she was stationed in Japan, Korea, Egypt and Algeria, all hotspots of US foreign politics and involvement before her final retirement. She died in 1985, more than forty years after the death of Arthur.

During these years many Austrian scientists who had emigrated returned for summer visits to Vienna and while there, they visited Arthur Haas who was building a dense web of relationships toward his goal of a permanent position as a professor. Yet his personal relationship began to suffer and his wife began to travel independently. Although Haas himself always claimed limited financial resources, she had inherited a substantial fortune from her father, which helped her to finance her excursions.

The second IIE lecture tour to the United States was delayed but eventually took place in 1931. Haas gave lectures on the new concept of particle waves and on questions of cosmology, an emerging topic in the scientific community. His visits covered universities all over the United States. Letters sent by Haas to his wife provide a rich and entertaining description of the academic environment of US universities at the time. With this trip, US academic institutions were very much interested in having Haas. However, the financial shortages caused by the world economic crisis did not allow for a sufficiently attractive offer and so, Haas was not convinced to abandon his actuary position, which by that time generated a considerable income.

This chapter gives some insight into the developments of the Jewish citizenry within the Habsburg empire, exemplifying the Haas family and describing the economic success of the broader family in the 19th century. Arthur Haas grew up in the Moldavian city of Brno in the wealthy environment of the Strakosch sugar dynasty in the Austrian Hungarian Empire. He enjoyed a protected upbringing in a privileged family.

The Vienna Academy of Sciences was an important institution for Austrian scientists. While Haas was primarily in charge of the organization and coordination of academic activities in the natural sciences, he found enough time to follow his own interests, publishing several books on topics of modern science. He also maintained an intense letter exchange with members of the scientific community. In this way he became a well-known and highly regarded member of the German and also Anglo-Saxon science community.

In the development of the new nuclear model, Haas worked closely with scientists from the University of Chicago. After a meeting in Chicago, where he had presented a talk on his latest results, he collapsed on the stairs of the conference hotel. He never recovered.

This chapter provides insight around the intellectual and academic life of Austrian and German universities at the turn of the last century. Arthur Haas’ success at high school turned into struggle as he tried to become an experimental physicist. Gottingen provided him with an intellectually strong and scientifically challenging environment, which he enjoyed despite his dislike of German student culture. Failure in the progress of his PhD project took him back to Vienna to seek a PhD in theoretical physics with Ludwig Boltzmann. The suicide of Boltzmann curtailed this plan, leaving Haas to write and submit a thesis on the historical philosophical development of physics concepts.

The dark years are the last years of Austrian independence in the shadow of Nazi Germany. Haas himself was under steady attack by Nazi sympathizers, in both Austria and Germany, who wanted him as a Jew to be removed from his post at the Vienna Academy. Haas responded by writing books for the public, describing the benefits of the scientific approach versus the pseudo-scientific claims made by Nazi representatives and followers. These years were further darkened by the murder of Dollfuẞ. Afraid of traveling to Germany, Haas sent his wife to negotiate with German publishers about his publishing income. In a number of rather entertaining reports, she describes the political changes that were taking place in Germany and the German publishing world. At last, Haas has the long-awaited position in America, albeit a temporary post.

It is a well-established fact that the generation of the heavy elements occurred in stars—the Cauldrons of the Cosmos—via multiple complex nuclear reaction processes during stellar life and death. This paper will address the question of the first step, the formation of heavier elements such as carbon and oxygen from the primordial elemental abundance distribution in first stars. This nucleosynthesis can be facilitated by nuclear clustering of primordial isotopes in hot and highly convective first stars, provided that a helium rich or hydrogen depleted environment is available. The paper will summarize the associated nuclear reactions and the nucleosynthesis paths linking $$^4$$ He to $$^{12}$$ C. This will be based on an analysis of new experimental data for several of the anticipated nuclear reactions, and the role they might play at different temperature and density conditions in first star matter.

This chapter describes the nature of the IIE as a post-war institution in the United States. The IIE was primarily founded with the goal of attracting promising central European scientists to American universities in order to raise the relatively low academic profile of these institutions. Many German and Austrian scientists followed this call in the difficult post-war years, and many of these were former students of Haas’, while he himself was considered a bit too old to be employable. Haas did not share this opinion.

Haas sought to combine his ideas on cosmology with the idea of a higher being, whose existence he saw reflected in the universal constants of physics. He developed close relationships with Catholic visitors and developed several lectures to find proof of the existence of God, going back to many of his original arguments from his younger years. In this idea Haas diverged from Canon Lemaitre, one of the famous cosmologists at the time, who was spending a sabbatical year at Notre Dame.

Haas maintained his interests in the history of science and with the help of the famous and influential science historian Karl Sudhoff, he was appointed in 1914 as docent for science history and as lector of the Poggendorff Journal at the University of Leipzig. He gave several successful lectures on the topic but also gradually developed a strong interest in theoretical physics.

The rise to power of the Nazi party in Germany also generated dark shadows for Austria, which turned to its own fascist government model while also maintaining the participation of the Jewish community. Haas saw himself as a member of the party led by Austrian Chancellor Engelbert Dollfuẞ, believing that a church-supported movement would shield Austria against Nazi terror. While increasingly worried, he turned his thoughts and scientific interests more and more to cosmology and the role of the fundamental constants in the greater picture of physics. In this, Haas followed the ideas of Arthur Eddington. During these years Haas published the first book on the topic of cosmology.

Arthur Haas’ high school education in Brno occurred in an enlightened environment which stimulated a broad range of intellectual interests from antiquity to physics, and also awakened his sensibilities and competitive spirit. The latter relied on positive feedback from friends and teachers. This chapter also provides insight into pedagogical developments during the late Habsburg empire.

The right to teach did not provide permanent employment and Haas continued his career while relying on his own private means of support. He was also trying to build a social network toward permanent employment as a faculty member at one of the Austrian universities. Growing anti-Jewish sentiment in academia prevented success despite several initially promising opportunities. The death of his father and the lingering sickness of his mother made his personal situation more difficult.

This chapter gives an overview of Vienna’s academic life and the struggles for young scientists seeking an academic career in an extremely competitive environment. During this time of revolution in physics, with the theory of relativity and new ideas on thermodynamics and spectroscopy, Haas initially tried to maintain his course of combining historic with scientific interests. Although this failed, Haas developed a first model to combine the new concept of the energy quantum with spectroscopy. His goal was to give the Planck constant h a physical meaning in the framework of the atom model.

This chapter describes the first IIE sponsored lecture tour of Arthur Haas through the eastern part of the United States in 1927. The tour was a great success, with Haas talking about nuclear energy as the energy source of the future, although he did not succeed in generating a position. Upon his return to Austria, he continued publishing and generated contacts with British and US publishing houses and, indeed, many of his books became translated bestsellers in the United States. This led to a number of invitations from US universities and Haas began planning a second lecture tour to the United States, again sponsored by the IIE.

Despite considerable differences in personality, temper, and vivacity, Haas and Huber decide to marry, a decision that was primarily hampered by the lack of financial resources that Haas considered necessary for a successful marriage. This chapter relies to a large extent on the exchange of personal letters during this particularly difficult year of 1924. The correspondence includes the personal and economic difficulties of a young physicist without employment, as he vacillates between big ambitions and little hope. The chapter ends with the marriage of Artur Haas and Emma Beatrice Huber.

Haas continued to teach during the first months of the war but was eventually drafted to the Army. His strong dislike of military affairs was a matter of record and the authorities charged him with the maintenance of the horse stables for the cavalry. His commanding officer had more appreciation for his academic titles and Haas enjoyed relatively peaceful but boring war years. He used the time to write a first textbook of modern physics. With the collapse of Germany and inner revolutionary struggles, Haas decided to return to Vienna. But, being from Brno, he saw himself identified as a Czech citizen.

Energy production in Type Ia x-ray bursts depends on a number of nuclear reactions that become efficient in a hot environment (up to 2 GK). Model sensitivity studies have been performed in an effort to better identify the reactions that have the largest effect, but these efforts are hampered by the high level of complexity of the astrophysical model and large nuclear physics uncertainties. In a recent study, the $^{24}\mathrm{Mg}(\ensuremath{\alpha},p)^{27}\mathrm{Al}$ reaction was found to significantly affect the energy generation in x-ray bursts. This manuscript reports the first study of the $^{24}\mathrm{Mg}(\ensuremath{\alpha},{p}_{1,2}\ensuremath{\gamma})^{27}\mathrm{Al}$ reaction at energies relevant for x-ray bursts. The branches to the $^{27}\mathrm{Al}$ excited states increase to a small degree the estimates of the total astrophysical $^{24}\mathrm{Mg}(\ensuremath{\alpha},p)^{27}\mathrm{Al}$ reaction rate.