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Warehouses are big architectonical structures mostly made of spruce wood and utilized as storage buildings principally by food traders in Northern Countries. Trondheim’s warehouses currently observable along the river Nidelva, date back between the 17th and half of the 19th century were mostly used to stock and process fish. Therefore, where the food goods were stored, residuals are expected to be still present and/or to be responsible for the formation of alteration products on the wooden surfaces as well as inside the wooden structure. Here we propose a characterization of residual and neo-formed compounds inside and on the surface of wooden logs by means of vacuum microbalance that allowed both to individuate the type of salts, as well as, to estimate the maximum water film thickness adsorbed on the wooden samples at 93% of RH. These data have been related to variations in the acoustic emission (AE) intensity detected at the log surface and to the wood moisture content measured with capacitive and resistance operating moisture meters. The application of three independent techniques have allowed obtaining interestingly information indicating their potentiality as decay assessment techniques in the field of historical materials and specifically in the study of salts weathering on wood. The methodology allowed identifying a clear relationship between the amount of water in logs as a function of their distance from the ground and variations in the amplitude of the acoustic emission signals.

Schemes for internal ro-vibrational cooling in Yb2 and Cd2, as well as 171Yb Bohm's spin-1/2 particle version of the Einstein‒Podolsky‒Rosen experiment based on photo-dissociation of (171Yb)2 are p...

A critical review of experimental studies and ab initio calculations of the low-lying ungerade excited and ground state interatomic potentials of Cd2 van der Waals dimer is presented. Consistency as well as discrepancies between experimental results and ab initio calculations are probed. In order to obtain better agreement with existing experimental data, fill in gaps in current knowledge and provide a unifying framework, advanced all-electron ab initio calculations were performed and simulations of the reported spectra were executed. From simulations of laser-induced fluorescence excitation and dispersed emission spectra, analytical and/or point-wise representations of the (51P1), B11u(51P1), a31u(53P1), (53P1) and c31u(53P2) excited-, and the (51S0) ground-state Cd2 interatomic potentials were obtained. The comparison of the ab initio calculated potentials with results of the analyses allows to illustrate a current state-of-the-art of theory-and-experiment correspondence for such a demanding sys...

Timber elements are major structural and architectural components in historic buildings and at the same time belong to the category of materials vulnerable to degradation. The recovery of 150-year old timber beams from a roof of a historic building made possible the non-destructive investigation of their response to cyclic loading. The experimental study carried out using the acoustic emission technique provided evidence that historic wood shows the load memory known as the Kaiser effect. The effect was observed for different loading and unloading time windows. The observations open up a new perspective for the determination of defects in wooden objects and constructions, important for assessing their possible structural instability.

Excitation spectra of CdNe, CdAr and CdKr complexes were recorded using the B31(53P1) ← X10+(51S0) bound ← bound and free ← bound transitions. A simulation of the dissociation continua formed by the free ← bound transitions in CdNe and CdAr permitted a determination of the repulsive part of the B31-state potential above the dissociation limit. The bound ← bound transitions in the excitation spectra of CdNe, CdAr and CdKr, and those previously recorded for CdHe and CdXe, were analyzed; by including their rotational structure and isotopic composition in the analysis, the characterization was improved. Morse functions for CdNg (Ng = noble gas) (also Lennard-Jones (12-6) for CdHe) and ab initio calculated interatomic potentials were tested for the representation of the B31-state potential above and below the dissociation limit. It was also found that previously reported ab initio calculated potentials for CdNe, CdAr, CdKr and CdXe could be modified and used. The B31-state rotational constants could be determined from the simulation of the ( υ ′ ; υ ″ ) = (2; 0)-band rotational profile in CdAr.

The method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in an investigation of vibronic and isotopic structures in the D 1 0 u + (6 1 S 0 ) and F 3 1 u (6 3 P 2 ) electronic energy Rydberg states of Cd 2 . Laser-induced fluorescence excitation spectra recorded using the D 1 0 u + ← X 1 0 g + (5 1 S 0 ) and F 3 1 u ← X 1 0 g + transitions in the region of 206-218 nm provided spectroscopic characteristics of the excited states and allowed constructing of their intratomic potentials. Isotopic structures recorded in the (v',v") bands of the D 1 0 u + ← X 1 0 g + transition were used in determination of the D 1 0 u + state vibrational characteristics (ω' e x' e , ω' e x' e ) and v' assignment The v 0,0 recorded directly in the F 3 1 u ← X 1 0 g + transition enabled determination of the bottom of the F 3 1 u state potential well. Valence ab initio calculations of Cd 2 interatomic potentials were performed with relativistic and spin-orbit effects taken into account. The experimental results were compared with results of the ab initio calculations. A free-jet expansion of Cd 2 as a source of entangled atoms for a test of Bell's inequality was analyzed.

Isotopic and rotational structures of the ( υ ′, υ ″) = (13,5), (14,5), (16,5) and ( υ ′, υ ″) = (0,1)–(6,1) vibrational bands of the E 3 Σ + ← A 3 Π 0 + and E 3 Σ + ← B 3 Σ 1 + transitions in CdAr, respectively, as well as the ( υ ′, υ ″) = (21,9) of the E 3 Σ + ← A 3 Π 0 + transition in CdKr were investigated using free-jet expansion beam and laser excitation. An optical–optical double resonance process was employed from the X 1 Σ 0 + + to the E 3 Σ + Rydberg via the A 3 Π 0 + or B 3 Σ 1 + intermediate electronic state. The structure of the bands with resolved isotopic structure was analyzed including their rotational structure. Analysis and simulation of the bands provided values for vibrational and rotational characteristics of the states. The analysis extended our previous low-resolution studies performed for the E 3 Σ + ← A 3 Π 0 + and E 3 Σ + ← B 3 Σ 1 + transitions.

Laser-induced fluorescence excitation and dispersed emission spectra of Cd2 recorded using the c 3 1 u ( 5 3 P 2 ) ← X 1 0 g + and b 3 0 u + ( 5 3 P 1 ) → X 1 0 g + transitions, respectively are reported. In the excitation to the c31u state, red-shaded vibrational components of several υ′ ← υ″ = 0, 1, 2, 3 progressions and Δυ = 0,1 sequences were identified. In the emission from the b 3 0 u + state, well resolved υ′ = 0,1,2,3,4 → υ″ transitions were recorded using a spectrograph with CCD camera. Analyses of the spectra provided an improved characterization of the b 3 0 u + , c31u and X 1 0 g + states involved in the transitions. The results were compared with our ab initio calculations and those obtained experimentally in earlier studies.

Laser-induced fluorescence dispersed emission spectra recorded using the C 1 Π 1 ( υ ′ ) → X 1 Σ 0 + transition in ZnKr, ZnAr and ZnNe complexes are reported. The complexes were produced in a continuous free-jet beam crossed with a pulsed dye-laser beam. The spectra were recorded using a spectrograph equipped with CCD camera. The recorded profiles displayed characteristic Condon internal diffraction patterns. The patterns consisted of reflection type continuous features corresponding to bound → free transitions and bound → bound transitions. In simulation of the spectra, M–S(9.09, 7.81), M–S(10.86, 10.32) and M–S(14.49, 8.91) Maitland–Smith M–S( n 0 , n 1 ) functions were found to represent the repulsive walls of the X 1 Σ 0 + -state potentials of ZnKr, ZnAr and ZnNe, respectively. The obtained results were compared with available experimental and theoretical representations of other studies.

Laser-induced fluorescence excitation spectra of CdRg (Rg = He, Ne, Xe) complexes were recorded at the D 1 Σ 0 + ← X 1 Σ 0 + bound ← bound and free ← bound transitions. In case of CdXe, analysis of the recorded profiles resulted in determination of the D 1 Σ 0 + -state potential energy curve and ground-state dissociation energy. In case of CdHe and CdNe, analysis of the free ← bound profiles provided a repulsive part of the D 1 Σ 0 + -state potential. Valence ab initio calculations of the ground- and excited-state potentials and electronic transition dipole moments of the studied transition were performed taking scalar-relativistic and spin-orbit effects into account. The results were supplemented with those for CdAr and CdKr of our earlier study.

Laser-induced fluorescence excitation spectra observed using the D 1 Σ 0 + ← X 1 Σ 0 + transition were used to determine the D 1 Σ 0 + -state potential in ZnNe, ZnAr and ZnKr. The complexes were produced in a free-jet expansion beam and excited with a dye-laser beam from the ground to the excited state. Analysis of the unstructured free ← bound profiles yielded information on the short-range repulsive part of the D 1 Σ 0 + -state potential. Ab initio calculations of the potential energy curves for the ground and excites states as well as for electronic transition dipole moments of the studied transition were performed taking scalar relativistic and spin–orbit effects into account.

Rotational profiles of the 228Cd2 isotopomer recorded in the (υ′, υ″) = (26, 0), (27, 0), (42, 0), (45, 0), (46, 0), (48, 0) vibrational bands of the A 0 u + ← X 0 g + transition were analysed. As a result, the B υ = 26 ′ = 0.0311 ( 5 ) cm - 1 , B υ = 27 ′ = 0.0309 ( 5 ) cm - 1 , B υ = 42 ′ = 0.0279 ( 5 ) cm - 1 , B υ = 45 ′ = 0.0278 ( 5 ) cm - 1 , B υ = 46 ′ = 0.0275 ( 5 ) cm - 1 and B υ = 48 ′ = 0.0272 ( 5 ) cm - 1 excited- as well as the B υ = 0 ″ = 0.0207 ( 5 ) cm - 1 ground-state rotational constants of the (114Cd)2 were determined. The analysis allowed determining the absolute values for the R e ′ ( A 0 u + ) = 2.71 ( 7 ) A and R e ″ = 3.76 ( 4 ) A excited- and ground-state bond lengths, respectively. The obtained result – the R e ″ – distinctly shorter than that obtained with assumption of pure ground-state van der Waals bonding, supports a theoretical prediction of a covalent admixture to the bonding. Analysis of the partially-resolved rotational profile recorded in the (υ′, υ″) = (38, 0) band of the same isotopomer recorded at the B 1 u ← X 1 0 g + transition allowed estimating the B υ = 38 ′ = 0.0317 ( 2 ) cm - 1 rotational constant in the B1u state.

A method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in investigation of vibrational and rotational structures in the 1 0 u + ( 5 1 P 1 ) and 11u(51P1) electronic energy states of Cd2. Laser induced fluorescence (LIF) excitation and dispersed fluorescence spectra recorded at the 1 0 u + - X 1 0 g + and 1 1 u - X 1 0 g + transitions provided spectroscopic characteristics of the excited and ground states as well as a shape of the repulsive part of the ground-state potential energy curve (PEC). Rotational structures of the 228Cd2 isotopomer recorded in the (υ′,υ″) = (45,0) and (38,0) bands of the 1 0 u + ← X 1 0 g + and 1 1 u ← X 1 0 g + transitions, respectively, were used for a direct determination of the ground- and excited-state bond lengths. Moreover, the 11u-state interatomic potential was obtained numerically using an inverted perturbation approach (IPA). The position and height of the 11u-state potential barrier was determined and compared with results of ab initio calculation. Analysis of Condon-internal-diffraction (CID) profiles in the bound-free dispersed fluorescence spectrum resulted in determination of a degree of repulsion between two ground-state Cd atoms in the dimer, supporting a hypothesis of a covalent admixture to the dominant van der Waals (vdW) bonding.

Analysis of a first-time recorded rotational structure of the υ ′ = 45 ← υ ″ = 0 band of the 1 0 u + ( 5 1 P 1 ) ← X 1 0 g + transition in 228 Cd 2 is presented. In the interpretation, an influence of a nuclear spin intensity alternation and rotational levels symmetry properties are taken into account. From the analysis, the B υ ″ = 0 = 0.0206 ± 0.0005 cm - 1 and B υ ′ = 45 = 0.0277 ± 0.0005 cm −1 rotational constants, and the R e ″ = 3.77 ± 0.04 A and R e ′ = 2.94 ± 0.03 A bond lengths are determined for the 114 Cd 114 Cd. The obtained value of R e ″ is close to that obtained with an assumption of a covalent admixture to the dominant van der Waals bonding of Cd 2 and is smaller than that derived with an assumption of pure dispersion forces.

New ab initio and revisited experimental studies of the interatomic potentials of ungerade excited and ground electronic energy states of the heavy van der Waals (vdW) dimer Hg2 were used as a “test-bed” for theory-to-experiment comparisons. Representations of the lowest excited- and ground-state Hg2 interatomic potentials were proposed, by using a new analytical approach as well as by using an inverted perturbation approach (IPA). The comparison of the new ab-initio calculated potentials with the results of the analyses illustrates an improved theory-to-experiment agreement for demanding heavy systems such as Hg2.

Results of new all-electron ab initio calculations and revisit of experimental studies of the interatomic potentials of lower-lying ungerade excited and ground electronic energy states of the Hg_{2} and Cd_{2} van der Waals complexes are used as probes of discrepancies between theory and experiment. From simulations of the previously and presently measured LIF excitation and dispersed emission spectra new analytical representations of the excited- and the ground-state interatomic potentials are proposed. An inverted perturbation approach was also used to improve the studied interatomic potentials. The comparison of the new ab-initio calculated potentials with the results of the analyses illustrates an improve theory-to-experiment agreement for such a demanding system like Hg_{2} or Cd_{2}.

Acoustic emission (AE) is defined as a transient elastic wave produced by the rapid release of energy stored in material under stress. The energy propagates itself as ultrasound and sound waves, and can be detected at the surface using a piezoelectric sensor which converts the vibration of the surface into an electric signal. The AE technique has recently become an important non-destructive tool to gain insight into the evolution of damage in materials. It is widely used as a laboratory method in material science and civil engineering. However, it has not been applied sufficiently in the field of cultural heritage, mainly due to the great variety of historic materials and limited knowledge about their physical properties. In comparison with other non-destructive techniques AE possesses some very important advantages – it is simple in application and does not require any external stimulation of the object. Due to its high sensitivity (which is both an advantage and disadvantage) complications in interpretation of the recorded signals are unavoidable, especially during long-term monitoring in noisy environmental conditions. The main problem is how to distinguish AE signals related to damage from signals which originate from other non-destructive processes as well as from ambient noise. In this paper a comparison of AE signals measured for different materials (stone samples, timber joist specimens) and different destructive and non-destructive processes, including mechanical tests, is presented. The proper evaluation of the results obtained in the laboratory can help to distinguish between AE signals related to material damaging and non-damaging processes. The presented work demonstrates the potential of AE as a practical tool to assess the risk of mechanical damage to historic building materials also at different moisture contents or in varying state of decay.

The method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in an investigation of vibronic and isotopic structures in the D¹0(u)⁺ (6¹S₀) and F³1(u)(6³P₂) electronic energy Rydberg states of Cd₂. Laser-induced fluorescence excitation spectra recorded using the D¹0(u)⁺ ← X¹0(g)⁺(5¹S₀) and F³1(u) ← X¹0(g)⁺ transitions in the region of 206-218 nm provided spectroscopic characteristics of the excited states and allowed constructing of their intratomic potentials. Isotopic structures recorded in the (υ',υ'') bands of the D¹0(u)⁺ ← X¹0(g)⁺ transition were used in determination of the D¹0(u)⁺ state vibrational characteristics (ω'(e)x'(e), ω'(e)x'(e)) and υ' assignment. The ν(0,0) recorded directly in the F³1(u) ← X¹0(g)⁺ transition enabled determination of the bottom of the F³1(u) state potential well. Valence ab initio calculations of Cd₂ interatomic potentials were performed with relativistic and spin-orbit effects taken into account. The experimental results were compared with results of the ab initio calculations. A free-jet expansion of Cd₂ as a source of entangled atoms for a test of Bell's inequality was analyzed.

Laser-induced fluorescence excitation spectra of MeRg (Me = Zn, Cd; Rg = He, Ne, Ar, Kr, Xe) complexes were recorded using the D 1 Σ 0 + ← X 1 Σ 0 + free ← bound transition. The complexes were produced in their ground state in a free-jet expansion beam and excited with a dye-laser beam directly to the excited state. Analysis of free ← bound unstructured profiles provided a shape of the repulsive part of the D 1 Σ 0 + -state potentials. Valence ab initio calculations of the ZnRg and CdRg ground- and excited-state potentials and electronic transition dipole moments for the studied transition were performed, taking scalar relativistic and spin–orbit effects into account. Results of the calculations show regularities and correlations in the repulsive branches and bound wells of the X 1 Σ 0 + - and D 1 Σ 0 + -state potentials as well as provide information on the bonding character in both electronic energy states. The trends were compared with available experimental results for ZnRg and CdRg as well as for MgRg and HgRg.

Laser-induced fluorescence excitation and dispersed fluorescence spectra of a cadmium dimer recorded using the B11u ↔ X10+g transition are reported. In the excitation, well-resolved isotopic structure of several υ' ← υ'' = 0 vibrational components (υ' from 34 to 40) as well as a free ← bound unstructured band was recorded. The B11u-state interatomic potential was derived using the 'inverse-perturbation' fitting method. In the dispersed fluorescence after selective excitation of the B-state υ' = 39 level of the 226Cd2 molecular isotopic component, a Condon internal diffraction pattern was recorded and simulated, confirming the υ'-assignment. Analysis of the dispersed fluorescence spectrum yielded information on the repulsive branch of the ground-state potential. The experimental results were compared with results of ab initio calculations as well as with experimental results of earlier studies.