Hideto Kanamori

Spin polarization in SO photochemically generated from SO2

The photochemical processes induced in sulfur dioxide by 193 nm excimer laser excitation have been investigated by examining vibration‐rotation transitions of the reaction product SO with the use of tunable infrared diode‐laser spectroscopy. Only X 3Σ− ground‐state SO molecules were observed. About 70% of the nascent SO molecules were found to be in the v=2 state, about 20% in v=1, and some in v=5. The rotational distribution in each vibrational state differed significantly from the thermal distribution, and was shifted towards higher rotational levels in lower vibrational states. The electron spin was observed to be polarized in the v=1 and 2 states in a direction either parallel or antiparallel to the rotational angular momentum, i.e., the F1 and F3 spin sublevels are more populated than the F2 level in these states. This selective population was not observed for v=5. The origin of the spin polarization is discussed in terms of spin‐orbit mixing between the C state and a repulsive triplet state of SO2....

Infrared diode laser kinetic spectroscopy of the ν3 band of C3

Infrared diode laser kinetic spectroscopy was applied to reaction intermediates generated by the photolysis of diacetylene and allene at 193 nm. A strong band was observed around 2040 cm−1 and was assigned to the ν3 band of C3 . The observed spectrum was analyzed by using an energy level expression for a linear molecule; higher‐order centrifugal distortion terms were necessary to be included in the least‐squares fit. The band origin was determined to be 2040.0198 (8) cm−1. The rotational and centrifugal distortion constants obtained suggest the presence of a potential barrier at the linear configuration in both the ground and ν3 states.

Infrared diode laser kinetic spectroscopy of the CCH radical ν3 band

Infrared diode laser kinetic spectroscopy was applied to the photodecomposition of acetylene at 193 nm to observe the ν3 (C–C stretching) band of the CCH radical. More than one hundred absorption lines were observed between 1750 and 1900 cm−1, but none of them could have been assigned to the ν3 band. This is probably due to CCH molecules being excited to high‐lying vibrational states by the excess energy of the photolysis. In fact, when either hydrogen or deuterium was added to acetylene as a buffer gas, new absorption lines appeared and were assigned to the ν3 fundamental band. The band origin which was derived from the observed spectrum is 1840.5711(4) cm−1, in agreement with the result of a previous matrix study. The spin–rotation interaction constant was found to decrease by as much as 30% upon ν3 excitation, presumably because of mixing with the lowest excited electronic state.

Diode laser spectroscopy for monitoring the yield of metastable Cl from photodissociation of simple molecules

Time resolved spectroscopy of the atomic fine structure transition of Cl, 2P1/2–2P3/2 at 882.35 cm−1 is applied to derive relative yields of the metastable level 2P1/2 of Cl(Cl*) from the photodissociation by excimer laser radiation of KrF or ArF. Molecules such as HCl, CH3Cl, CH2Cl2, phenyl chloride, and PCl3 are studied, getting for the first time the possibility of systematic comparison of yields for Cl* and also of earlier results on heavier halogens obtained by other authors using different methods. Most yields determined in the present work are close to a value as calculated from the statistical weights of the two fine structure levels of Cl. This finding is related in a simple diabatic picture to the small spin–orbit interaction in Cl compared to that in iodine. Additionally some rate constants for the collisional quenching of the metastable Cl by the parent molecule are derived.

Vibronic bands of the CCH radical observed by infrared diode laser kinetic spectroscopy

Five infrared bands of the CCH radical were observed by diode laser kinetic spectroscopy. Two Π–Π type bands were assigned to hot bands from the (0110) state in X 2Σ+, namely to ν2+ν3−ν2 and 7ν12−ν12. The latter band was found to share the upper state with a Π–Σ type band, of which the lower state was the ground vibronic state. Two other Π–Σ type bands corresponded to transitions from the ν3 state in X 2Σ+ to two vibronic Π states. Simultaneous analysis of all the observed bands yielded molecular parameters with high precision including the ν2 fundamental frequency, which was determined to be 371.6034 (3) cm−1. The parity of each rovibronic level was determined unambiguously because Π–Σ+ transitions were observed, allowing us to choose the signs of K‐type doubling constants p and q uniquely.

Diode laser spectroscopy of C3: The ν2+ν3−ν2, 2ν2+ν3− 2ν2, and 2ν2+ν3 bands

The ν3 hot bands (011)–(010), (021)–(020), and the combination band (021)–(000) of C3 were observed by a diode laser spectroscopic method. The C3 molecule was produced by the photolysis of allene or by the discharge in cyclopropane or furan. Analysis gave molecular constants in each vibrational state and also the energy difference between (020) and (000). The derived vibrational frequencies were compared with the result of a Morse oscillator‐rigid bender internal dynamics (MORBID) calculation by Jensen.

Detection of the silylene ν2 band by infrared diode laser kinetic spectroscopy

The ν2 band of the silylene SiH2 molecule in X 1 A1 was observed for the first time in the gas phase by using infrared diode laser kinetic spectroscopy. Silylene molecules were generated by the photolysis of phenylsilane at 193 nm. The observed spectrum was analyzed to determine the rotational and centrifugal distortion constants in the ground and v2 =1 states and the band origin ν0 =998.6241(3) cm−1 with one standard deviation in parentheses. The significance of the derived parameters is discussed in detail.

Ab initio MO studies of van der Waals molecule (N2)2: Potential energy surface and internal motion

The equilibrium structure, potential energy surface and van der Waals (vdW) mode vibration of (N2)2 have been studied with high levels of ab initio calculations. The most stable structure is found to be a 45 deg. canted parallel structure of C2h. On the other hand, neither T-shape of C2v nor cross-shape of D2d is a stable structure, but they are transition state structures, which are contrary to the previous calculations. The out-of-plane motion changing from the 45 deg. canted parallel structure of C2h to the cross-shape of D2d has a higher barrier than the in-plane motion. The binding energy of two N2 monomers is about 80 cm−1 and the fundamental frequency of vdW stretching mode is estimated at 22 cm−1. A small energy difference of 5 cm−1 between the C2h and C2v structures implies that two N2 molecules move coherently like a gear rotation in the plane. This internal freedom of motion should make the rotational energy states extremely modulated, and therefore, a very complex spectrum pattern could be exp...

The vinyl radical investigated by infrared diode laser kinetic spectroscopy

A c‐type band was observed at around 895 cm−1 by infrared diode laser kinetic spectroscopy combined with the excimer laser photolysis of vinyl halides at 193 nm and was assigned to the CH2 wagging mode of the vinyl radical. The band was found to consist of two component bands separated by 0.0541(11) cm−1. Both component bands showed clearly the statistical weight in an alternative way, that is, if one shows the weight 1:3 for even:odd Ka levels, the other exhibits 3:1, indicating that the radical is of C2v effective symmetry, executing a double‐minimum motion probably associated with the C–H in‐plane rocking vibration. The upper states of the two bands were found to be perturbed weakly, possibly by a Coriolis interaction with the first overtone state of the C–H rocking mode.

Infrared diode laser kinetic spectroscopy of transient molecules produced by excimer laser photolysis: Application to the SO radical

Abstract Excimer laser photolysis has been incorporated with infrared tunable diode laser spectroscopy in order to observe infrared spectra, primarily vibration-rotation spectra, of transient molecules which are difficult to produce by other means such as electrical discharge. The method has been applied to SO generated by the photolysis of SO 2 , and the vibration-rotation transitions of SO in the X 3 Σ − state, each resolved into a fine structure triplet, have been identified for the bands of v = 1−0 up to 6−5 and have been analyzed to improve the precision of the vibrational parameters.