Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry最新文献

{"title":"Modulus of Natural Rubber Cross-Linked by Dicumyl Peroxide III. Some Molecular Interpretations, Possible Refinements of Theory, and Conclusions.","authors":"Lawrence A Wood","doi":"10.6028/jres.080A.051","DOIUrl":"10.6028/jres.080A.051","url":null,"abstract":"<p><p>The shear modulus <i>G</i> = 5.925 × 10 <i>^-</i> ³(<i>fp</i> - 0.45)<i>T</i>+<i>G*</i> (Part I), its energy component <i>G</i>* = 0.0684 (<i>fp</i> - 0.45)+ 2.70 (Part II), and the number of effective suh-chains per unit volume <i>v_e</i> = (<i>G - G*</i>)<i>/RT</i> are given detailed molecular consideration. <i>G</i> is given in Mdyn cm^-2 for rubber cross-linked by adding <i>p</i> parts of dicumyl peroxide per hundred of rubber, and heating until a fraction <i>f</i> of the peroxide is decomposed. <i>v_e</i> is found to be approximately twice the density of cross-links, after a correction for impurities and chain ends is made. It can not be computed as <i>G/RT</i> since only the entropy component of modulus is related to <i>v_e.</i> The sub-chains for the most highly cross-linked rubbers studied had a molecular weight of about 575 g mol^-1, corresponding to about 8 isoprene units. The modulus corresponding to no added cross-links is not zero. It is determined chiefiy by the energy component of the modulus; it does not arise from entanglements. The \"front factor\" is found to be unity. An extensive literature survey yields values of the quantity <i>RT</i>Ψ(<i>v</i> ₂), where Ψ (<i>v</i> ₂) is the Flory- Rehner equation function of <i>v</i> ₂, the equilibrium volume fraction obtained by swelling the cross-linked rubber. <i>RT</i>ψ (<i>v</i> ₂) is found to be greater than <i>G - G*</i> but not as large as <i>G</i> itself.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"451-463"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293352/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37758481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluorescence Quantum Yield Measurements.","authors":"J B Birks","doi":"10.6028/jres.080A.038","DOIUrl":"10.6028/jres.080A.038","url":null,"abstract":"<p><p>Four <i>molecular fluorescence parameters</i> describe the behaviour of a fluorescent molecule in very dilute (~ 10^-6 <i>M</i>) solution: the fluorescence spectrum <math> <mrow><msub><mi>F</mi> <mi>M</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> ;the fluorescence polarization <i>P_M</i> ;the radiative transition probability <i>k_FM</i> ; andthe radiationless transition probability <i>k_IM</i> .These parameters and their temperature and solvent dependence are those of primary interest to the photophysicist and photochemist. <math> <mrow><msub><mi>F</mi> <mi>M</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> and <i>P_M</i> can be determined directly, but <i>k_FM</i> and <i>k_IM</i> can only be found indirectly from measurements of the secondary parameters,the fluorescence lifetime <i>τ_M</i> , andthe fluorescence quantum efficiency <i>q_FM</i> ,where <i>k_FM</i> =<i>q_FM/τ_M</i> and <i>k_IM</i> =(1-<i>q_FM</i> ) <i>τ_M.</i> The <i>real fluorescence parameters</i> <math><mrow><mi>F</mi> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> , <i>τ</i> and <i>ϕ_F</i> of more concentrated (<i>c</i> > 10^-5 <i>M</i>) solutions usually differ from the molecular parameters <math> <mrow><msub><mi>F</mi> <mi>M</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> , <i>τ_M</i> and <i>q_FM</i> due to concentration (self) quenching, so that <i>τ</i> > <i>τ_M</i> and <i>ϕ_F</i> < <i>q_FM.</i> The concentration quenching is due to excimer formation and dissociation (rates <i>k_DMc</i> and <i>k_MD</i> , respectively) and it is often accompanied by the appearance of an excimer fluorescence spectrum <math> <mrow><msub><mi>F</mi> <mi>D</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> in addition to <math> <mrow><msub><mi>F</mi> <mi>M</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> , so that <math><mrow><mi>F</mi> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> has two components. The <i>excimer fluorescence parameters</i> <math> <mrow><msub><mi>F</mi> <mi>D</mi></msub> <mrow><mo>(</mo> <mover><mi>v</mi> <mo>¯</mo></mover> <mo>)</mo></mrow> </mrow> </math> , <i>P_D</i> , <i>k_FD</i> and <i>k_ID</i> together with <i>k_DM</i> and <i>k_MD</i> , and their solvent and temperature dependence, are also of primary scientific interest. The <i>observed</i> (technical) <i>fluorescence parameters</i> <math> <mrow><msup><mi>F</mi> <mi>T</mi></msup> <mrow><mo>(</mo> <","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"389-399"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293345/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Calorimetric Detection of Excited States.","authors":"James B Callis","doi":"10.6028/jres.080A.042","DOIUrl":"10.6028/jres.080A.042","url":null,"abstract":"<p><p>Calorimetric techniques offer the photophysicist and photochemist the opportunity to measure a number of parameters of excited states which may be difficult to obtain by other techniques. The calorimetric strategy seeks to measure the heating of a sample resulting from radiationless decays or chemical reactions of excited states. Heating is best measured through volume and pressure transducers, and four calorimeters based on these are described. With calorimetric instrumentation one can perform measurements on samples in the gas, liquid and solid phases over a wide temperature range. Moreover time dependent processes with time constants ranging from microseconds to seconds are amenable to study. Examples of the application of calorimetric techniques to the determination of quantum yields of fluorescence, triplet formation and photochemistry are given.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"413-419"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293348/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calculations of Configurations of Doubly Ionized Copper (Cu III).","authors":"J Sugar, W C Martin","doi":"10.6028/jres.080A.052","DOIUrl":"10.6028/jres.080A.052","url":null,"abstract":"<p><p>The energy levels belonging to the configurations 3<i>d</i> ⁷4<i>s</i> ² and 3<i>d</i> ⁸ <i>nℓ</i> (<i>nℓ</i> = 4<i>s</i>, 5<i>s</i>, 4<i>p</i> 5<i>p</i>, 4<i>d</i> 5<i>d</i> 4<i>f</i>, and 5<i>g</i>) have been calculated. The radial energy integrals were treated as parameters and adjusted to give a least-squares fit to the observed levels. Two- and three-body effective electrostatic interactions for equivalent electrons were included, as well as two-body effective interactions for inequivalent electrons. Strong configuration interaction between 3<i>d</i> ⁷4<i>s</i> ² and 3<i>d</i> ⁸4<i>d</i> was taken into account. Values of the parameters are given for all the above configurations, and the calculated levels are given for all except 3<i>d</i> ⁸4<i>s</i> and 3<i>d</i> ⁸4<i>p</i> (for which essentially equivalent results have been published). Leading eigenvector percentages are given in appropriate coupling schemes.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"465-476"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293353/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37758480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oscillator Strengths for Lines of Ionized Uranium (U II).","authors":"Charles H Corliss","doi":"10.6028/jres.080A.045","DOIUrl":"https://doi.org/10.6028/jres.080A.045","url":null,"abstract":"<p><p>Oscillator strengths for 49 lines of U II recently measured by Voight can be used to calibrate the intensity scale of the U II lines in the NBS Tables of Spectral-Line Intensities and derive a larger set of oscillator strengths of lower precision but consistent with the new measurements. The standard deviation of the differences between the two sets of <i>gf</i>-values for the 49 lines is 29 percent. Oscillator strengths of that precision are given for 776 additional lines from the NBS Intensity Tables. The uncertainty in absolute value is 67 percent.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"429-438"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293350/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vapor Pressure of Water at Its Triple Point.","authors":"L A Guildner, D P Johnson, F E Jones","doi":"10.6028/jres.080A.054","DOIUrl":"10.6028/jres.080A.054","url":null,"abstract":"<p><p>The vapor pressure of water at its triple point was measured with exceptionally high accuracy by realizing it with a special apparatus and measuring the pressure with the NBS precision mercury manometer. The vapor pressure apparatus had a system for circulating the liquid water. Actual triple point conditions were established with a thin sheet of freshly distilled liquid flowing down over an exposed mantle of ice frozen on a vertical well. This technique reduced non-volatile contaminants and the vapor was repeatedly pumped to remove accumulated volatile contaminants. A diaphragm pressure transducer was used to separate the water vapor from the helium used to transmit the pressure to the manometer. The value found for the vapor pressure of water at its triple point was 611.657 Pa with an uncertainty of ± 0.010 Pa from random errors, computed at 99 percent confidence limits. The systematic errors are estimated to be insignificant relative to the random errors.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"505-521"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293355/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37758483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cancer Detection by NMR in the Living Animal.","authors":"I D Weisman, L H Bennett, L R Maxwell, D E Henson","doi":"10.6028/jres.080A.048","DOIUrl":"10.6028/jres.080A.048","url":null,"abstract":"<p><p>The purpose of this paper is to review <i>in vivo</i> NMR experiments [1, 2] on a transplantable tumor in mice and to discuss the feasibility of using noninvasive NMR for cancer detection in humans.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"439-450"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293351/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the Actinometric Measurement of Absolute Luminescence Quantum Yields.","authors":"J N Demas, B H Blumenthal","doi":"10.6028/jres.080A.041","DOIUrl":"10.6028/jres.080A.041","url":null,"abstract":"<p><p>The theory of the measurement of luminescent quantum yields using chemical actinometry is described. The sample's emission intensity is measured by nearly completely surrounding the sample with an actinometer solution, and the excitation intensity is directly measured with the same type of actinometer. The ratio of the measured sample emission intensity corrected for the fraction escaping through the excitation ports to the measured excitation intensity is the absolute luminescence yield. Equations, a suitable cell design, and computer calculated correction factors for different cell dimensions and optical densities are given. The absolute yield of the actinometer is not needed, only its relative response with wavelength. New quantum-flat actinometers which should greatly simplify the measurements are described.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 3","pages":"409-412"},"PeriodicalIF":0.0,"publicationDate":"1976-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5293347/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bidirectional Reflectometry. Part II.: Bibliography on Scattering by Reflection from Surfaces.","authors":"Joseph C Richmond,&nbsp;Jack J Hsia","doi":"10.6028/jres.080A.022","DOIUrl":"https://doi.org/10.6028/jres.080A.022","url":null,"abstract":"<p><p>In connection with the work on development of a high resolution laser source bidirectional reflectometer, a large number of papers were collected dealing with various aspects of the geometrical distribution of the radiant energy reflected from surfaces of different types. Each paper has been classified into one or more classes on the basis of its technical content. There are eight general classes, with several subclasses in some of the general classes. Because of the interest in this field, the bibliography is being published as a service to the public.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 2","pages":"207-220"},"PeriodicalIF":0.0,"publicationDate":"1976-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5296188/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bidirectional Reflectometry. Part I.: A High Resolution Laser Bidirectional Reflectometer With Results on Several Optical Coatings.","authors":"Jack J Hsia,&nbsp;Joseph C Richmond","doi":"10.6028/jres.080A.021","DOIUrl":"https://doi.org/10.6028/jres.080A.021","url":null,"abstract":"<p><p>A laser-source bidirectional reflectometer that is fully automated and has angular resolution on the order of one degree has been designed and built. The direction of incidence and viewing can be independently varied over an entire hemisphere except for directions more than 77.5° from the normal, and the two directions must be at least 2.5° apart. Bidirectional reflectances for 15 samples of black and white coatings are presented.</p>","PeriodicalId":17018,"journal":{"name":"Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry","volume":"80A 2","pages":"189-205"},"PeriodicalIF":0.0,"publicationDate":"1976-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5296187/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37757423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}