Chemists have puzzled for the past 30 years over the strange behavior of ozone molecules in the Earth’s atmosphere.

Ozone (O₃), a gas known for its ability to absorb the sun’s potentially harmful ultraviolet rays in the stratosphere, performs that function when it splits into a single oxygen atom and an O₂ oxygen molecule and subsequently recombines.

Scientists 30 years ago discovered that when ozone breaks up, its O₂ photofragment showed a strong preference to its rotational states with even quantum numbers, over odd quantum numbers.

Why?

Distinguished Professor Hua Guo in UNM’s Department of Chemistry and Chemical Biology, with colleagues from Texas A&M University, has the answer.

In a paper published in 2020 in the Proceedings of the National Academy of Sciences, Guo explains how he solved the problem and why it matters.

“The rotational quantum number dictates how fast the O₂ molecule rotates and it contains important information about how the O₃ molecules break up in an excited electronic state,” Guo said. “The O atom is largely formed in its excited electronic state and it can have a large impact on the formation of the hydroxyl radical, which serves as the detergent in cleaning various pollutions in Earth’s atmosphere.”

Using a supercomputer due to the complexity of the calculations required, Guo’s team was able to solve the differential equation and definitively explain why the 02 photofragment disproportionately prefers rotational states with even quantum numbers.

According to Guo, “the even-odd propensity in the O₂ rotational states stems from preference of O₃ to break up within the molecular plane.” While plans for follow-up research have not been made at this time, Guo explained the importance of better understanding the processes of how ozone forms.

The Tamarind Institute at UNM is having an important birthday, which it celebrated with a curated selection of lithographs spanning six decades of collaborative printmaking that was revealed online each month through February and with a limited-edition pandemic-themed print.

Each year Tamarind selects an artist who produces a featured print for the institute’s Collector Club. The Collectors Club is limited to only 95 members who pay a yearly subscription fee to access the featured print. The latest Collectors Club artist is Jaune Quick-to-See Smith (’80 MA), who created “Coyote in Quarantine,” a nine-color lithograph that reflects the global pandemic and public health crisis.

Painter and printmaker Quick-to-See Smith is an enrolled member of Confederated Salish and Kootenai Nation, who grew up in Montana and now lives in Corrales. Despite the pandemic, the world-famous lithography institute’s team of printers worked with Quick-to-See Smith remotely through the summer to produce the print.