Deheng Shi

Sulfur monoxide radical has widely been detected in outer space using ground-state spectroscopy. The a ¹Δ₂ and b ¹Σ⁺₀₊ states of this radical have low excitation energies, and they possibly exist in outer space. In this work, the potential energy curves and dipole moment functions of the two states were evaluated using the complete active space self- consistent field method, followed by the valence internally contracted multireference configuration interaction approach. The transition line positions, oscillator strengths, band transition dipole matrix elements, Einstein A coefficients, and Franck–Condon factors of all transitions were calculated for lower vibrational levels at rotational angular momentum quantum number J up to 150. The transition line positions calculated in this study are in good agreement with the experimental results. The rovibrational transition became noticeably weak at Δυ > 5. Comparing the results of a ¹Δ₂ and b ¹Σ⁺₀₊ states reported in this paper with the previous values, we conclude that these results are the most accurate and complete to date.

This work endeavors to study the effect of surface oxidization on the normal spectral emissivity of red copper T1 samples at 1.5 μm. The normal emissivity is measured over a temperature range from 800 to 1100 K during a 6-h heating period. The radiance emitted by the specimens is received by an InGaAs photodiode detector, which works at 1.5 μm with a bandwidth of approximately 20 nm. The temperature of sample surface is obtained by averaging the readings of two thermocouples, which are symmetrically welded in the front surface of specimens near the measuring area. The strong oscillation of emissivity appears only during the initial heating period at each temperature, which is affirmed to be connected with the thickness of oxide layer. The interference effect is discussed between the radiation stemming from the oxide layer and the radiation from the underlying metal substrate, which is responsible to the strong oscillation. The uncertainty of emissivity yielded only by the surface oxidization is approximately 2.9% to 14.3%. The temperature uncertainty generated only from the surface oxidization is approximately 2.5 to 8.8 K. The models of normal emissivity with heating time are evaluated at a certain temperature. A simple functional form is found to reproduce well the variation of normal emissivity with heating time, including the reproduction of strong emissivity oscillation occurring during the initial heating period.

This work strived to study the variation in the spectral emissivity of steel 316L specimens with wavelength at a certain temperature. The spectral emissivity and radiances from the specimen surface were measured by multispectral radiation thermometry at wavelengths of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and 2.1 μm and at temperatures from 800 to 1100 K in increments of 20 K. The specimen was heated and kept at a certain temperature in air for 6 h. The temperature of the specimen surface was measured by two thermocouples, which were symmetrically welded onto the front surface of the specimens near the measuring area for accurate monitoring of the surface temperature. The average of their readings was regarded as the real temperature. Variation in the spectral emissivity with wavelength was studied at different temperatures and different heating times. Effect of surface oxidation on the fitting accuracy of the emissivity models was evaluated. Two favorite models were determined. With the radiant values measured by thermometry and in combination with the least-squares fitting technique, two favorite models were examined. On the whole, both the five-parameter LLWE and LWE models could yield the best overall temperature prediction and could farthest relieve the effect of surface oxidation on the accuracy of temperature prediction over the present wavelength and temperature ranges.

The transition dipole moments of the SiN radical are calculated by the valence internally contracted multireference configuration interaction (icMRCI) approach with the aug-cc-pV6Z basis set. The transition probabilities of spontaneous emissions are computed between the eight lowest-lying doublet states. The vibrational band origins, Einstein coefficients, and Franck–Condon factors of all the spontaneous emissions involved are evaluated. The rotationless radiative lifetimes of the first 15 vibrational levels were determined to be approximately 10⁻³–10⁻⁵ s long for the A²Π state, 10⁻³–10⁻⁷ s long for the F²Π state, 10⁻⁶–10⁻⁷ s long for the C²Π state, 10⁻⁶ s long for the D²Σ⁻ and E²Δ states, and 10⁻⁷ s long for the B²Σ⁺ and G²Δ states. It is observed that the rotationless radiative lifetimes quickly become shorter, with an increase in the vibrational level for the A²Π and F²Π states. The Einstein coefficients of many emissions are large for the B²Σ⁺–X²Σ⁺, B²Σ⁺–A²Π, C²Π–X²Σ⁺, C²Π–A²Π, D²Σ⁻–A²Π, E²Δ–A²Π, F²Π–X²Σ⁺, F²Π–A²Π, and G²Δ–A²Π systems. However, the emissions are very weak for the F²Π–D²Σ⁻ system. The vibrational levels and rotational constants of each state are determined and the spectral range of each transition system is evaluated. The vibrational band origins are compared with the available experimental ones. The spectroscopic routines for detecting the unobserved states are proposed. These results can be employed to measure emissions, in particular those of interstellar clouds and stellar atmospheres.

This work investigates the transition dipole moments (TDMs) and transition probabilities of electric dipole emissions between the X²Π, B²Σ⁺, B^′2Π, D^′2Π, C²Σ⁻, C^′2Δ, F²Σ⁺, and P²Π states of the PO radical. The TDMs of 23 pairs of states are calculated by the internally contracted multireference configuration method with the aug-cc-pV6Z basis set. The vibrational band origins, Franck–Condon factors, and Einstein coefficients of all the spontaneous emissions are evaluated. The rotationless radiative lifetimes of the vibrational levels are approximately 10⁻⁷–10⁻⁸ s for the B²Σ⁺, C²Σ⁻, C^′2Δ, P²Π, and F²Σ⁺ states; 10⁻⁴–10⁻⁵ s for the B^′2Π state; and 10⁻¹–10⁻² s for the D^′2Π state. The Einstein coefficients of many emissions are large for the B²Σ⁺–X²Π, B^′2Π–X²Π, C^′2Δ–X²Π, C²Σ⁻–X²Π, F²Σ⁺–X²Π, P²Π–X²Π, P²Π–B^′2Π, and P²Π–D^′2Π systems. Almost all the spontaneous emissions arising from the D^′2Π state are very weak. The vibrational band origins of these emissions extend from the UV into the far-infrared spectra. The radiative lifetimes and vibrational band origins are compared with available experimental and theoretical values. According to the radiative lifetimes and transition probabilities obtained in this paper, some guidelines for detecting these states spectroscopically are proposed. The TDMs and transition probabilities reported here are considered to be reliable and can be used as guidelines for detecting similar transitions, especially those in interstellar space.