12C 14N Research Articles

Fermi resonance perturbations between (ν β= n) and (ν σ=1, ν β= n−2) states in the rotational spectrum of HCN…HF

A useful graphical method for the assignment and analysis of the effects of Fermi resonance in rotational spectra has been devised and applied to vibrational satellites in the microwave spectrum of H 12C 14N…H 19F. The analysis leads to a value of 7.4 cm −1 for the cubic potential constant k σββ.

A redefined anharmonic potential energy surface of HCN

A set of cubic and quartic anharmonic potential constants, k ijl , k ijlm of the normal mode potential energy surface of H 12C 14N was determined by a least-squares analysis applied to 79 most recently observed values of the vibrational and rotational energies. The calculated constants are a second solution of the fitting besides that of T. Nakagawa and Y. Morino ( Bull. Chem. Soc. Jpn., 42, 2212–2219 (1969)).

Conservative Replication of Double-Stranded RNA in Saccharomyces cerevisiae by Displacement of Progeny Single Strands

Saccharomyces cerevisiae contains two double-stranded RNA (dsRNA) molecules, L and M, encapsulated in virus-like particles. After cells are transferred from dense (13C 15N) to light (12C 14N) medium, only two density classes of dsRNA are found, fully light (LL) and fully dense (HH). Cells contain single-stranded copies of both dsRNAs and, at least for L dsRNA, greater than 99% of these single strands are the positive protein-encoding strand. Single-stranded copies of L and M dsRNA accumulate rapidly in cells arrested in the G1 phase. These results parallel previous observations on L dsRNA synthesis and are consistent with a role of the positive single strands as intermediates in dsRNA replication. We propose that new positive strands are displaced from parental molecules and subsequently copied to produce the completely new duplexes.

Conservative replication of double-stranded RNA in Saccharomyces cerevisiae by displacement of progeny single strands.

Saccharomyces cerevisiae contains two double-stranded RNA (dsRNA) molecules, L and M, encapsulated in virus-like particles. After cells are transferred from dense (13C 15N) to light (12C 14N) medium, only two density classes of dsRNA are found, fully light (LL) and fully dense (HH). Cells contain single-stranded copies of both dsRNAs and, at least for L dsRNA, greater than 99% of these single strands are the positive protein-encoding strand. Single-stranded copies of L and M dsRNA accumulate rapidly in cells arrested in the G1 phase. These results parallel previous observations on L dsRNA synthesis and are consistent with a role of the positive single strands as intermediates in dsRNA replication. We propose that new positive strands are displaced from parental molecules and subsequently copied to produce the completely new duplexes.

Classical chaos and quantum simplicity: Highly excited vibrational states of HCN

Direct overtone spectra of H 12C 14N, H 13C 14N, and H 12C 15N have been measured between 15 000 and 18 500 cm−1 with a precision of 0.001 cm−1. These were obtained using intracavity photoacoustic spectroscopy, with a fully automated laser system. The spectra are unperturbed. The transition energies and rotational constants are in good agreement with predictions of first order anharmonic constants. Classical trajectories for HCN have been computed on the best experimentally parameterized potential, and found to be stochastic 12 990 cm−1 above the ground state. Quantal density of states were computed for HCN and show that if extensive vibrational coupling occurs, the observed states would be highly perturbed. The simplicity of the observed states is shown to be expected given a Franck–Condon type limitation on significantly perturbing states. The results show the inapplicability of classical dynamics for predicting the dynamics of molecular vibrations.

Rotational spectra of excited vibrational states of F 12C 15N. Equilibrium structure of cyanogen fluoride

The rotational spectra of F 12C 15N have been observed in the ground state and in the (01' 0), (02° 0), (10° 0), (20° 0) and (00° 1) excited vibrational states. From analysis of the spectroscopic data available for F 12C 14N, F 12C 15N and F 13C 14N the equilibrium structure of cyanogen fluoride has been evaluated.

Laser Stark spectroscopy of DCN and DC 15N

Using a CO laser, laser Stark resonance spectra were measured for the CN stretching fundamentals (the 00 01-00 00 bands) of D 12C 14N and D 12C 15N near 1925 cm −1. Laser Stark resonances were also measured for the hot band 01 11-01 10 of D 12C 14N. In addition to accurately determining the band centers, dipole moments are given for the different vibrational states involved.

Infrared spectrum of H 12C 14N and H 12C 15N

The high-resolution spectrum of H 12C 14N has been measured near 4870 and 6060 cm −1. The following bands have been identified and analyzed: 01 12-00 00, 02 02-01 10, 02 22-01 10, 04 01-00 00, 11 11-00 00, 12 01-01 10, and 12 21-01 10. The CN stretching fundamental ( ν 3) of H 12C 15N has also been measured near 2100 cm −1. This fundamental is found to be 3 cm −1 higher than previously reported. Other bands that have been identified in the H 12C 16N spectrum are 03 10-00 00, 04 00-01 10, 04 20-01 10, and 01 11-01 10.

Analysis of the microwave rotation spectrum of silyl cyanide, SiH 3CN, in its ground and vibrationally excited states

The rotational spectrum of silyl cyanide, SiH 3CN, has been studied by microwave spectroscopy. A detailed analysis of the transitions in the excited states of the ν 3, ν 4, ν 7, and ν 8 modes has been carried out. In particular the v 8 = 1, 2, 3, and 4 vibrational satellites have been subjected to a complete vibration-rotation analysis. Ground state transitions of 28SiH 3 12C 14N, 29SiH 3 12C 14N, 30SiH 3 12C 14N, 28SiH 3 13C 14N, and 28SiH 3 12C 15N have all been studied in natural abundance. The overall study has yielded a large amount of detailed vibration-rotation data. The effects of quadrupole interactions have been taken into account. To confirm the analysis, computer simulated spectra have been compared with those observed.

HCN radio emission from Comet Kohoutek (1973f)

Radio emission spectra of the J = 1−0 ground state transition of H 12C 14N has been detected in comet Kohoutek (1973f) before and after perihelion passage. The HCN gas production rate is about 10 28 molecules sec −1 at a heliocentric distance of ∼0.4 AU. Multiple Doppler shifts in the observed spectrum suggest jets with velocities ranging up to several km sec −1.

Nuclear shielding and magnetic hyperfine structure of hydrogen cyanide

A millimeter-wave molecular beam maser has been used to resolve the magnetic hyperfine structure of hydrogen cyanide. The spin-rotation interaction constants have been measured for the three nuclei 14N, 13C, and H. The paramagnetic nuclear shielding factors have been calculated for the three nuclear sites. The spin-rotation constants for 14N in H 12C 14N, for H in H 12C 14N and for 13C in D 13C 14N are + 10.4 kHz, −3.7 kHz, and +15.0 kHz, respectively. The respective paramagnetic shielding factors are −408.98 × 10 −6, −73.40 × 10 −6, and −249.52 × 10 −6.

Force field of cyanogen from vibrational spectra of isotopic species

The Raman spectra of ( 12C 14N) 2, ( 13C 14N) 2, and ( 12C 15N) 2 in the vapor phase have been studied. From the isotope shifts of several levels the Fermi resonance constant, W 01000-0002 00 = 41 cm −1, has been determined. The observed data, together with earlier infrared data, allow a determination of all the first order anharmonic corrections and thus of the fundamental harmonic frequencies. From these results, force constants and compliance constants of a general quadratic force field are calculated and discussed.